Fixit Log

What skills to learn, what tools to get
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Sclass
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Fixit Log

Post by Sclass » Wed Mar 07, 2018 2:26 pm

I fix a lot of stuff to save money. I thought I'd post up a few things here as I complete them since members like money saving fixes. Feel free to post up some of your own. I'm always eager to learn new ways to make money saving repairs.

I'll start out with my latest project. My Carrier Furnaces. Repairmen can get expensive on these. In California, we are not allowed to fix these without a contractor's license and we cannot even buy parts over the counter. At my mom's, when the furnace broke in the past her caregivers would just call the repairman and send a bill. This got into the hundreds of dollars. Sometimes they just came in and did something silly like tightening some electrical connections. So I started by telling the ladies to call me first and let me take a look.

Using YouTube, I became my own HVAC repairman. Simple tools like screwdrivers and wrenches along with a free Harbor Freight Tools digital voltmeter was all it took to do a blower motor, a flame sensor cleaning, an ignitor replacement and most recently on my residence, two controller board swaps.

I have some photos of the controller board swaps. The specific information regarding the operation, removal and replacement of your particular controllers can be found on YouTube. I'll fill in some general purpose tips that helped. In other words, this is not a tutorial, but more a slideshow and journal for your entertainment and inspiration.

This is what I have in my crawl space. Two of these. They have been getting flakey lately. Sometimes they don't light up and heat. FIRST DISCONNECT THE POWER OR OPEN THE BREAKER.
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It turns out they both failed in the same way. Using a voltmeter I was able to determine that the call signal came from my wall controls but it didn't get further than turning on the inducer blower and ignitor. A handy flow chart for debugging found on the inside of the furnace indicated that the next step should have been turning on the gas. I wasn't getting gas flow nor was I getting voltage at my gas valve. The limit sensors all checked out good on my meter and so did the pressure switch. There was really nothing left but the controller board.

So I open the doors and expose the controller pcbs. Simple eight bit microcontroller designs to check a bunch of sensors and sequence lightup. Not rocket science.

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expose the board.
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find the part number
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Go search online for a replacement. I found some on ebay for $40 each. They were used which may be problematic because they could fail for the same reason as the old ones. I learned a little more about this too and I'll discuss this at the end.

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searching, searchhing, searching...,

After obtaining replacements I carefully photograph the wiring connections so I know how to put it all back together. Photos are free.

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Swap out the old boards and install the newer ones. Button it all up. Presto, working furnaces. I'm nice and warm now.

But why did those thirty year old boards fail anyway? This is the next level of complexity. If you can figure out what is wrong with the boards and replace the components you can save even more. Right now I'm in $80. But what if a $0.15 electronic component is failing on the boards? Well, as the movie said, "I gots to know man."

So the boards go to the bench in the garage.

I find a leaky electrolytic capacitor on both. It seems to be related to the gas valve actuation circuit but I cannot figure out how or why they need this big 47uF capacitor to close a relay. I check the relays and find their contact resistance is 2x out of spec at 200 mohms. (okay, I did this on a Kelvin connection four wire ohmmeter, not quite Harbor Freight). So the relay to activate the gas is worn. I study the circuit and figure the capacitor is used to provide a pulse of current to the relay to close it, then as it charges up the current consumption drops and the relay is held closed using a small resistor. We call it catch and hold drivers for solenoids and relays. The original designers never thought thirty years down the road the hot environment in the furnace would slowly boil out the electrolyte in the capacitor and render it useless thus making it impossible to turn the gas on.

Here is the removed components, cap and relay. Note the oily substance on the board.
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I pulled the relay and noticed Fujitsu rates these for 10^5 electrical connections and a quick back of the envelope calculation shows my heater has turned on and off about 40% more times than that. Curiously I think it is because my "smart" thermostat controls temperature to within 1 degree F and with this tight control band the heater turns on and off about three times as often as the original Carrier designers anticipated. So out go the worn relays.

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working, working, working.
Desoldering work.
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New parts show up in mail. Yep, $0.15 parts. What happened to Radio Shack? I cannot get this stuff over the counter anymore. I guess selling single components to fixit people like me for dimes isn't a business.
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Not quite done yet but soon I'll test my repaired boards. I guess I'll have some spares in the meantime. This is why new boards that cost 2x as much may be a wiser choice. I got cheap and got working old boards on ebay. Hope this inspires people. YouTube is a game changer. I hope their new monetization scheme doesn't destroy the good DIY content.

ffj
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Re: Fixit Journal

Post by ffj » Wed Mar 07, 2018 7:48 pm

I love this kind of stuff. I'll definitely keep an eye out for more contributions and I'll have to start documenting some of the stuff I come across.

Good job finding the problem. Sucks having to crawl around under your house having to get access to this stuff.

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Sclass
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Re: Fixit Journal

Post by Sclass » Wed Mar 07, 2018 10:58 pm

Just tried out one of my refurbed boards. It works. Amazing. I wish I’d known to just swap the cheap relay and capacitor instead of buying entire boards for $40.

Oh well, I cannot perfectly optimize all expenditures. :)

More fixes to come.

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Chris
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Re: Fixit Journal

Post by Chris » Wed Mar 07, 2018 11:31 pm

Thanks for starting the topic; hope to see interesting things here.

It's almost always the capacitors. The first time I fixed something like this was my parent's LCD monitor. Like you, I hit up Youtube. On eBay I even found sellers listing replacement capacitors for specific LCD models. Really makes you wonder how many devices end up getting landfilled over a busted 15 cent part. At least enough that someone has a side business selling baggies of 4 capacitors at a 10x markup.

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Sclass
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Re: Fixit Journal

Post by Sclass » Thu Mar 08, 2018 6:12 am

Hey that reminds me of fixing my 14 yo microwave oven two months ago. It just stopped working according to my SO.

I almost tossed it but I noticed it totally quit...as in no display, beep, heat etc. like a circuit breaker popped. I opened it and sure enough there is a big 30A fuse in there that just opened. A quick search online shows videos on how to diagnose and replace the fuse. They sell them at Home Depot. They were actually called “Microwave Fuses.” All news to me.

Microwave works like new. Apparently the fuse melts after a decade of tea. Saved $250 (it’s a nice one) and kept my trashcan empty.

Next time your microwave totally quits, open it up and check the fuse. Unless you want a new one.

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Re: Fixit Log

Post by jacob » Thu Mar 08, 2018 7:44 am

I changed the title to Fixit Log and made it sticky.

Farm_or
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Re: Fixit Journal

Post by Farm_or » Thu Mar 08, 2018 7:55 am

I'm very impressed. 25 years ago, I did component level repairs on PCB' s on the job. It was for ultra expensive, proprietary (zero schematics) semiconductors manufacturing equipment.

I was able to apply my college education on the integrated components and visual and likelihood of component failure (power resistors, electrolytic capacitors, switching relays) there is an order. I was able to learn sections of the board and associated with failures. I saved the company a lot of money, but the boss didn't notice. After awhile, I just started tossing them on the recycling pile with everyone else.

Your soldering and desoldering skills are impressing too. Some guys just get it. I had to take classes on technique. Some joints can be difficult to safely remove.

I recently used you tube to fix a difficult, intermittent problem with my oiil burning furnace. It was a luxury to be able to leave the house this winter without worrying about the pipes freezing.

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Sclass
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Re: Fixit Log

Post by Sclass » Thu Mar 08, 2018 10:27 am

I tried to keep the soldering and desoldering simple. This fix can be done with a cheap soldering iron, solder wick and a vacuum solder sucker (a Soldapult as they used to be called). All cheap and easy stuff. How to vids on YouTube. Well within the amateur zone.

The great thing is now we can get very good quality soldering equipment for more complex repairs for cheap out of China. In my photos above I show a hot air station for SMT that only cost me $30 shipped from China. That is a more difficult skill to master but I think one can pick up the skill by watching YouTube as well and then practicing on junk boards. I learned by watching my techs over the years. Because I literally learned by spying on techs (specifically hired for smt skills) I think one can learn this skill with YouTube and a good hot air tool like mine. I did a search on hot air soldering, drag soldering etc. and they show all the tricks.

As for impressing, I replaced an iPhone WiFi transceiver chip last year after watching this video. This is where I start calling things hard. It took four attempts over two days for me to get the phone working properly over WiFi. I almost gave up and junked he phone after ruining three chips. This operation is average difficulty for a good SMT tech.

https://www.youtube.com/watch?v=8FUGLEdfwKw&sns=em

My point is a lot of this can be learned online and the equipment is cheap. We live in a great time.

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Re: Fixit Log

Post by Farm_or » Thu Mar 08, 2018 12:03 pm

Good stuff. I don't want to get carried away, because I think I could fill this thread up. Here's a few of recent contributions:

IPhone 5s. Replaced battery last week. Took some painstaking attention to detail and about four hands and ten minutes. Saved $###

Magnavox combo vhs/DVD. Repaired DVD. Damaged ribbon cable. Had to buy set of ten replacement for $10 to get the one that was needed. Saved $###

Oil furnace repair. Would not reliably stay lit. New nozzle, strainer, filter and adjustments to air/ fuel ratio. Cost $50, saved $###

1989 f150 alternator quit at 45k miles. $0.25 for new brushes. Saved $##.

Washing machine, front loader. Broken tumbler spring and shock absorbers. $25 parts and three hours labor (mine). Saved $###

I'm gonna stop there...

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BlueNote
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Re: Fixit Log

Post by BlueNote » Thu Mar 08, 2018 10:30 pm

@Sclass: That makes me want to learn about how to repair electronics.

I fixed the family coffee grinder a while back using a 3d printed part along with some online instructions and a youtube video.

You don't need a 3d printer these days either you can just send your design into a professional place and they'll print the part for you and send it to you, much more cost effective. There's a ton of free designs out there for lots of common replacement parts too.

In my case the 3d printed part was a better design and made of more durable material. The coffee comes flying out of the grinder now, it's almost too good.

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Sclass
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Re: Fixit Log

Post by Sclass » Fri Mar 09, 2018 12:24 am

BlueNote wrote:
Thu Mar 08, 2018 10:30 pm
In my case the 3d printed part was a better design and made of more durable material. The coffee comes flying out of the grinder now, it's almost too good.
That’s really cool. Come to think of it my Braun burr grinder always leaves a clod of grounds in the little port. I had no idea this was actually the problem. I just lived with it.

I look forward to the further evolution of 3d cad and printing...so I can easily get into it. My experience with CNC milling was that the variability in steps between the design and the machine specific CAM programs made it impossible for me to send anything other than step or dxf (geometrical data) out to a job shop accompanied with a litany of desired specs. The fact that a 3d printing shop can take a file and make a part from it is very intriguing. Is it like sending a pdf to a printer? Aren’t there a ton of things to spec to get from that pretty gear model to the finished part?

Edit - OMG I did a search and pretty much answered my question. This opens up some really unique repair possibilities.

https://lifehacker.com/five-best-3d-pri ... 1706410803

Stahlmann
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Re: Fixit Log

Post by Stahlmann » Fri Mar 09, 2018 4:46 pm

https://imgur.com/a/rnZUy

I did this 2 years ago. After 2 month they were dead because electronic. I need to work to have rather "tough hands" (I'm mech eng, but my understanding of doing mechanical stuff is pretty low, due to lack of practice; there is no better way to learn than doing, even for sake to be capable of optimalizing in the future work of blue collars) than to play with electronic. I've got in my past Electronics I, Electotechnics I, also Physics I & II, bur trying to memorize facts instead of understanding brought me here... anyway I'm pretty clueless. Sclass, if you had spare time please share something on this (yep, I'm beggar). I'd be glad to read such piece. Your topic on thermostat is beyond for me (this show my understanding of this field). Probably being able to combine electro+mech skills is a killer (my technical director operates in this field).

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Sclass
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Re: Fixit Log

Post by Sclass » Sat Mar 10, 2018 9:51 am

No Stahlmann. YouTube. That’s one of the themes of this log. Me teach you? That’s so medieval. I’m too lazy anyway. Why work when a machine can do a better job.

Don’t worry, you didn’t miss much in class. That’s the theory. The practical stuff is digested down on YouTube. It may not get you a job but you’ll be able to keep a few dollars (euros) in your pocket. Happy fixing.

Curmudgeon
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Re: Fixit Log

Post by Curmudgeon » Sat Mar 10, 2018 3:38 pm

I've fixed very expensive boards on a dishwasher, an oven, and a refrigerator. Each time it was a relay.

I also fixed an inexpensive DVD player once, this time it was a bad capacitor. These are easy to spot by their bulging tops.

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7Wannabe5
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Re: Fixit Log

Post by 7Wannabe5 » Sun Mar 11, 2018 7:54 am

Super cool thread!

I have been using my often overloaded rolling suitcase on rough winter sidewalk terrain too much lately, so I demolished one of the front wheels. So, I took off the broken wheel and both of the back wheels, and screwed the mirror image back wheel and fitting on to the front. It doesn't stand up by itself anymore, but it does roll again nicely. Cost $0.

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Kriegsspiel
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Re: Fixit Log

Post by Kriegsspiel » Sun Mar 11, 2018 8:32 pm

I looked on Amazon for a few minutes for a new pair of gym shorts, becuase I noticed I had been flashing a bunch of grundle at the gym lately. But fuck, I already have a needle and thread, why do I need a new pair of shorts? I sewed up my crotchal area and now have a functional, non-grotesque pair of gym shorts.

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Sclass
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Re: Fixit Log

Post by Sclass » Tue Mar 13, 2018 10:28 pm

More Furnace work and Coffee Roaster tweaks.

Ohh, I'm not out of the woods yet on my furnace. One furnace works great on the new electronics. The other is better but it quits every six hours. I can power cycle it and it comes back to life but for some reason it doesn't want to always ignite. It puts out a fail to ignite code. So back into the crawl space I go.

After some voltmeter probing I find that my board is putting out good voltage to the gas valve but the gas valve doesn't open one time in ten. It seems sticky. I totally missed this the first time through. Probably because there were two problems, a worn relay on the board and this sticky valve. There is nothing like multiple failures superimposing themselves on one another to confuse logical troubleshooting. So...I missed a sticky valve that fails to fire every few hours. The furnace does three retries then shuts down. That's why I could go half a day with the thing running great and then poof, heat gone. So I remove the valve. Take plenty of photos as usual.

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It's held in with some small screws and a tapered pipe fittings for the inlet and outlet. I get it out and replace the valve with a new/used one from ebay for $35 shipped. More YouTube for valve replacement.
Easy, just like water pipes but with special gas thread sealing compound. All is working now. The valve is supposed to be non serviceable according to youtube. You just buy a new one. I know better to try to fix something that can leak toxic flammable gas and burn the house down. The unit is screwed together with security screws. I get it, they don't want anyone to fix this thing. Just throw it out. But why did it fail? Hey, I gots to know. The valve seems to be sticking. Is it contaminated? Broken?

Chinese security screw bits. $4 on ebay.

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Open it up. Take photos. Pay attention to all the little springs falling out. Hmmm. Hmmm.
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So the block is a cast manifold with three rubber valves inside it. Two are solenoid actuated and use strong springs to close the valves in a fault condition. This thing is basically designed to slam shut if anything goes wrong. The mechanical valve on the left corner is the on off knob valve. There is an interesting cone shaped valve in the center - the black rubber disk. This is connected to the regulator diaphragm that opens and closes to maintain a steady differential pressure from inlet to outlet if the gas supply pressure fluctuates. My gut feel is the problem is here. I could hear the solenoid valve clacking when I applied power but gas still wouldn't flow.
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This looks like the main gas valve. When the electronics calls for heat, this opens letting gas into the manifold. The other solenoid opens a feedback circuit to regulate pressure via the big red diaphragm.
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This is the plunger on the main gas solenoid valve. The rubber is still flexible on the seal. It is a little smudged up with oil. The plunger is in good shape and has a loose fit in the coil. I don't see this as sticking. Electrified the pull is strong. No issues here.
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As mentioned above, the other side of the body has this big red diaphragm in it to operate a cone shaped pintle valve. It is actuated purely on differential pressure inlet-outlet to regulate pressure. Pressure gets too high downstream the pintle chokes down, too low it opens up. Note the flimsy little spring that acts to push the diaphragm along with the gas pressure. These are the forces that will open the valve.
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Under the diagphragm we have this spring loaded shaft that pushes the pintle valve. It has a stiff spring on it. So I'm thinking the error signal gas pressure pushes the diaphragm along with the wimpy spring and compresses this stiff spring to open the valve. This is a delicate balance. I noticed the white plastic shaft was greasy and sticky in the bore.
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The problem is this pintle valve is gummy with oil residue. It is just sticky enough to provide some seal friction that may be keeping the pintle stuck for several valve actuations (recall I have three tries before the furnace quits). If this is sticky, it may explain why the furnace lights on the second or third try but eventually fails after several hours. This little cone valve may be jamming in the bore of the seal. Since it isn't actuated by the magnetic force of a solenoid but rather a wimpy spring and feedback gas pressure, it may be my sticking problem. Clearly, if this valve jams, the gas will not flow. Sometimes I got lucky tapping the valve with a mallet and it would open and light the burner. The rubber seal is in good shape though it's a little oily and dirty.
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At the end of the day I don't know. I put it all back together but tagged it as "do not use". It was really tempting to reinstall it and see if I actually fixed it by cleaning the valve seats. But, I like the house in white, not black.

Coffee Roasting
Okay, well on to my second fix. I am stuck doing taxes so what better way to procrastinate than fix stuff around the house. This morning my air popper that I use for coffee roasting quit. It has been quitting lately just before the second crack so it totally stalls the process of getting a dark roast. Oddly it comes back to life an hour after I put it on the shelf. It has been quitting earlier and earlier and now the roast is way too light for my consumption. Time to tear it open and start fixing.

oops, looks like somebody used security screws again. I guess I'm not supposed to be in here. Time for the special screwdrivers.
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Ok, thats better.
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Gawd this thing is cheap inside. I guess I could have bought another but it probably would have quit in the same way. Might as well find out what is opening up and short over it.

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Getting deeper. Looks like the fan is wired in series with the heater. Ugh! Who designed this. So I originally wanted to wire it so the fan would go on all the time and the heater could be activated with the side switch. The idea being I'd be able to kill the heat on demand while still running the fan so I could get to the right level of goodness. Looks like the two circuits need to be wired in series so I don't think it'll happen. Now I just need to find out why it shuts down early and stop that.

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More screws more disassembly. Somebody told me "if you see a screw, unscrew it." I'm not sure this is good advice but it certainly gets things moving forward. What I'm seeing here is a one time thermal fuse (the silver cylinder) that will open if the thing is on fire. The gold thing is a thermal switch that opens when it gets hot but remakes contact on cool down. This is what is killing my motor and heater halfway through my roast.

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I've got to close this up somehow. It gets hot and the bimetal leaf bends up and breaks the contact on the left. No good. Quits too early. Hmmm. Hmmm. How do I short it? Foil? Solder? Paper clip? What if I want the thing to quit before it melts the plastic case in my hand?

Ahh, the answer. Think first then do.

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Bend the little tab a little closer to the contact. Then it has to deflect more to break the contact during heating. I'll test it next week. I have enough dark roast to last me a few days.

Back to taxes. Ugh.

Farm_or
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Re: Fixit Log

Post by Farm_or » Thu Mar 15, 2018 6:57 am

Great stuff sclass! I love your methodical curiosity.

A little warning for others about YouTube: there are a lot of hack jobs on display. Sometimes it is hard to tell when a job is being demonstrated correctly, or if it's a hack job.

For example: the celica that we recently purchased started making intermittent wheel bearing noise. Dealer wants upward of $600. Screw that! Ordered QUALITY bearing and seal kit for $50 and began browsing YouTube for hints. I found a guy demonstrating the job fairly well, right up to the end - and the most important part. He hammered the bearings castle nut on with an impact gun! No! The bearing preloaded has to be precise with a torque wrench! Viewer beware.

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Sclass
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Re: Fixit Log

Post by Sclass » Thu Mar 15, 2018 5:28 pm

Farm_or wrote:
Thu Mar 15, 2018 6:57 am
Great stuff sclass! I love your methodical curiosity.

A little warning for others about YouTube: there are a lot of hack jobs on display. Sometimes it is hard to tell when a job is being demonstrated correctly, or if it's a hack job.
So true. Thanks for reminding everyone. I like to read the comments. People will often speak up and call out a hack job. Or worse, downright dangerous fixes.

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Sclass
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Keeping the Plumber outta my pocket

Post by Sclass » Tue Mar 27, 2018 11:51 am

Fixed a drippy faucet on the tub. SO got me to do it by just leaving the hot water running and walking away. :lol: That got my attention.

Basic tools - phillips screwdriver, 9/16" deep socket (tried open end spanner and rounded off two corners of the valve). Discovered a neat trick, I had turned the faucet off hard mainly to stop the drip, so when I unscrewed the valve I unscrewed the brass valve seat at the same time - by friction between the rubber seal and seat. No need for the fancy square shafted wrench. Consult YouTube for your specific system. Mine was Price Pfister = Price Fister :lol:

Oh yeah, another great tip, if you install Price Pfister, they will provide seals, cartridges etc. for life. So before installing, make sure your part numbers are in an obvious place like glued to the inside of the vanity where you'll find it. My tub is built in and I'll never be able to get the part numbers without a sledge hammer. I've called in on my sink faucets in the past and gotten free valve cartridges sent out. I keep extras zip tied to the flexible hoses under the sink just in case. Call the 1-800 number before you need them. Just lie about having a leak because eventually you'll have one. Good to keep a file on all installed hardware.

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Old rubber valve and seat. Oooooh look at the divot on the brass seat. No wonder it dripped.

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Thank goodness they sell this kit for $2.50 at Home Depot.

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Another fix. Hooray! Yeah, now to take my savings out to get some pastrami sandwiches...for the next few months. :lol:

edit - btw the bent thermostat trick on the air popper/coffee roaster worked great.

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