1941 Plymouth Temp Gauge

41PlySD · September 17, 2010, 11:20:10 PM

Tod, First of all thank you very much for your patience with me. I believe I'm getting it now. After I wrote the last post I then realized what you had said in your procedure..."The ether expands from the engine heat, it shoots up the capillary tube, and creates pressure to move the needle". It's not heat that makes the needle rise, it's pressure from the expanding ether! Here we were putting the gauge under water the other day because we thought the heat from the torch would peg the needle and ruin the gauge! LOL...Well, today I went to another friend at work that I knew had a set of very small drill bits. I brought the gauge head with me and expalined your procedure to him. He said "Well, if the tube is open we should be able to blow into it to raise the needle then"...Initially we couldn't raise the needle with a little air pressure from house air. I bet the other day when I heated the gauge block some solder created a blockage in there. We managed to get through that blockage with an .024" drill bit and then used a little house air again...and sure enough...the needle rose a bit with a little blow of the air gun...The capillary sure appears to be open now. Ok...There's 3 aftermarket gauges under my dash that the previous owner installed into my 41...One of them is a Temp. gauge and I bet it's what your describing as what I need for the donor gauge. I'll have to look to see if it's a mechancial type temp. gauge...Thanks again Tod, Bob

TodFitch · September 17, 2010, 07:12:28 PM

Quote from: 41PlySD on September 17, 2010, 01:57:25 PM... I do have about 3/8" of the tube hanging out of the gauge block. ... If I do decide to heat the block to remove this 3/8" length of tubing...do I have to take great care in how hot I get the gauge block? ...

I've only used a soldering iron or soldering gun when I've done this. And on my personal one I soldered the new tube to the block without damaging the gauge. So it should be possible.

However if you have 3/8" of the tube sticking out why not simply splice onto that? It sounds like there is a very good chance that the capillary is open and soldering a sleeve onto the tube is far easier than soldering a new tube into the block. Trust me on that, I've done it both ways and getting a good solder joint on the block is not easy.

41PlySD · September 17, 2010, 01:57:25 PM

Quote from: Jim Yergin on September 17, 2010, 09:55:03 AM
Is there any way to just change out the gauge face plates and use the replacement unit with the '41 face plate?
Jim Yergin

Very good thought Jim...My friend and I went back and forth on that one too. I probably could make it work by doing that but the needle is shorter and it comes up from the bottom. Mine comes down from the top. Unfortunately it would not be a direct swap of the face plate either. Drilling new holes in my face plate would be necessary and I'd still have the issue with the upside down needle. The rear mounting plate is larger as well and would have to be cut off because the clearance hole for the tube is not large enough to pass over the bulb. I'd also have to cut/bend my mounting plate to get it over the bulb as well. I thought about turning the whole gauge head upside down but then the movement of the needle would be backwards...right to left instead of left to right. Very undesireable results in my opinion.

Tod, Yesterday after I posted my reply to you I went in the lab (I'm doing this at work...shhh) and carefully cut off a very little bit of the tube and did find a tiny open hole in it...I couldn't see it before because the cutter that someone used on it years ago mashed the tube at the end. I do have about 3/8" of the tube hanging out of the gauge block. That hole is very small too!...The smallest drill I have is .039" and that was too big to fit in there to clear any debris out. I found a resistor and the solid wire on it fit in there tightly...I poked it in there and it seemed to be clear for about the 3/8" length of it. Now I'm hoping I didn't shove anything down in there...A small drill would be good to have to make sure it's cleared out. I don't know...perhaps I can save it?? Tod, If I do decide to heat the block to remove this 3/8" length of tubing...do I have to take great care in how hot I get the gauge block? I mean...If I have to peg the gauge to melt this solder will it ruin the gauge? That was my thought the other day when I submerged it in water...but that prevented me from heating it up enough to melt the solder and remove the tube.

Jim Yergin · September 17, 2010, 09:55:03 AM

Is there any way to just change out the gauge face plates and use the replacement unit with the '41 face plate?
Jim Yergin

TodFitch · September 16, 2010, 05:43:23 PM

I first did my gauge in the 1970s when I was younger and dumber. Or at least less experienced in not breaking things. On mine, I removed the old tube at the gauge head and then soldered in a new bulb and capillary tube from a modern replacement. The concept is much the same as the newer procedure I have written up on my web site. You just have a higher probability of getting a clogged capillary tube.

If there is any old tube coming out of the gauge head, I'd probably try to splice on to that. But, again, the one in my car has had the new tube directly soldered into the gauge head so you can do that if you must.

Please do not use an open flame to do your soldering. The bulb and tube contain ether which is highly inflammable. I've found that a high wattage soldering iron or soldering gun used for electrical work has enough power to do the job and it will be a lot safer for you.

41PlySD · September 16, 2010, 05:13:37 PM

Quote from: TodFitch on September 16, 2010, 04:07:25 PM
Please don't damage another working gauge to get yours repaired... You can use a cheap modern "mechanical" temperature gauge from your local auto supply store.

If you had "Googled" "temperature gauge repair" the first hit you would find is one on my site. Step by step with pictures:

http://www.ply33.com/repair/tempgauge

Thanks Tod for the great writeup/procedure....but I don't think it will work in my case. It was cut off too close to the gauge. I'd have to get what's left of the tube out of the gauge block....and doing that will require a good amount of heat which would ruin the gauge. That was my concern yesterday as we tried to remove the coil and tube. No worry...I will not cut into the old working gauge. That was also a concern I had yesterday. I did not want to ruin a good working gauge trying to fix mine...with no guarantees of actually fixing it.

TodFitch · September 16, 2010, 04:07:25 PM

Please don't damage another working gauge to get yours repaired... You can use a cheap modern "mechanical" temperature gauge from your local auto supply store.

If you had "Googled" "temperature gauge repair" the first hit you would find is one on my site. Step by step with pictures:

http://www.ply33.com/repair/tempgauge

41PlySD · September 16, 2010, 02:41:26 PM

Hi guys...Now moving onto another issue with the 41. The Temp gauge does not work because a previous owner cut the sending unit off near the back of the gauge. A friend at work brought in a working late 40's Mopar Temp gauge and it's a little bit different....but it seems to have the exact same sending unit/cable on it. Question: Has anybody ever unsoldered the sending unit/cable from the back of a Temp gauge? We tried to yesterday keeping the gauge sunmerged in water so we didn't overheat it...managed to heat it up enough with a propane torch to remove the external shield/winding off but the internal cable remains attached to the gauge block. Keeping the gauge in water seems to be working quite well as a heatsink...too well in fact because we can't heat the block up enough to melt the solder holding the internal cable in. Any advice would be appreciated. I have not touched the working late 40's Mopar gauge/sending unit. I want to make sure I can get the old (cut) one detached first.

Thanks, Bob