The Stovebolt Site Forums The Shop Area The Electrical Bay temp gauge

my 59 vilikng temp gauge is have fun with me.i replaced the gauge which was toast and sending unit.funny thing does sweep if u ground at wire from gauge or touch test light to gauge works fine other wise nothing. how many grounds on motor? i see the one at the starter....cdan

Are you sure the engine is hot? My 59 GMC temp. gauge just barely moves off COLD, and the engine has to run a long time for that. Also the heater and hoses do not get very hot. I think maybe the previous owner may have removed the thermostat. Plan on checking it later. May try putting some cardboard in front of the radiator, just for a test.
BTY, I did add an extra ground strap from the firewall to the frame, just in case of rust or not grounded good.

if the engine weren't well grounded it wouldn't crank or start -if you can ground the wire at the sender and the gauge moves, then maybe you got a defective sender [check it in pot of water on the stove] - or maybe you used some thread sealer on the sender? the sender needs to have a clean contact with the engine to get a ground

Bill

thanks 2 u both! i have ran the truck shot with a temp gun to get range. i have just replaced the sending unit again and after the 2nd go around with the brakes we will see if she finall works this time i used a 6469 from napa rather than a tu5 from the zone.

I am piggy backing this post with a question about my temp gage (55 first series with stock 235). My gage is "stuck" on hot. Before I replace the gage is there anything I can adjust? (Kinked thermocouple wire etc.)

Thanks,

Joe

I have just the opposite problem with mine. Wants to read hot even though actual temp is 180. Also tried different senders for different vendors. 1958 Chevy. Also a new gauge. Still shows hot when it ain't.

But if yours moves when grounded and works with test light, then the sending unit may be the culprit. You say you used a laser thermometer to check the heat, is it indeed running where it should heat wise yet your gauge isn't showing? Maybe thermostat stuck open or missing?

Guys,
This ain't rocket science. The sender is not a thermocouple, a device that produces an emf when heated. It is a variable resistor with a negative heat coefficient, resistance goes down as heat goes up. There are other like the King-Seeley type but that's for another time. Buy yourself a variable resistor, like maybe 0-200 ohms, a couple of wire jumpers and hook the resistor up in place of the sender. Power up the gauge and vary the resistance. If everything is ok the needle will move from cold to hot. you can use an ohmmeter to measure the resistance from cold to hot. You then will know what the resistance range your sender needs to be. BTW, this test can also be used on the gas gauge. Good luck.

There are no electrical wires to mine (1955 first series). Unless I missed something (I did poorly in Rocket Science class) :-)

There is no need for knowledge of the electrical/electronic aspects of rocket science in order to deal with the "mechanical" coolant temperature sender and the "mechanical" oil pressure sender on a 1955 truck engine.

I am out of my league in referring to physical principles, but I think that those mechanical gauges are related to a Bourdon tube, which pre-dates the Jet Age?

Maybe a rocket science class would help some of us understand the workings of a fuel gauge (even if we understand the steps for a diagnosis of a fuel-gauge problem).

Yes, if yours does not have wires, but just a small tube, then it operates with a thermocouple/bourdon type tube. Would be a mechanical type. So that seems to leave only 3 places to go wrong. I have only seen these as a complete unit with gauge,tube and sending unit made together.
1- Engine is really not getting hot enough.
2- Tube is bad, bent or broken inside.
3- Bad gauge.
I just jumped in here because I am in the same process of getting all my gauges to working. Got it down to just fuel gauge left.

Maybe this would help: http://www.ply33.com/Repair/tempgaugeuld help:

Bordon tube: Closed tube bent into a coil. The tube is filled with a liquid. When heated the pressure inside goes up and the tube tries to get straight. When it cools, pressure goes down, tube re coils. Simple. One end sits on the engine, other end is the gauge. Works until it don't. Why does it stop? Leak, crimp, and stuck. They last a long time but are not readily repaired. No voltage required. I just replace when they quit. Some one with more time and patience might try to fix or repair. But I don't see any advantage when there are replacements available. I hope this helps some.

One reason to try to fix them is to satisfy a sick need to make old parts like new again. Some of us are afflicted this way. BTW, has anyone successfully repaired one by using the bulb and its contents from a modern gauge?

Aren't they filled with ether? I have a mechanical style and it was rubbing against my oil pressure sensor tube. The oil pressure tube gets hot, melts the temp sender tube and a big fireball erupts under my dash. Scared the heck outta me. Got a new one at pepboys for $28.

Just between us girls, I don't think he liked the Rocket science remark.

Sorry guys, I didn't say anything about the mechanical type as I was addressing questions about the electrical questions. I think you have a good understanding of the Bourdon type.
SIDEBAR: Just to clear up the question of what predates what. The Bourdon tube was patented in France in 1849. The Chinese were using rockets in the 13th century, so someone had to understand rocket science even back then. Please don't get upset, just having some fun and good luck with your gauges.

52Carl: by all means figure how to fix one. Copper tube is easy compared to steel. Medium inside is most likely alcohol, but ether might be what was used. That stuff is dangerous so be safe. The meter movement is simple but small so get some big eyes to help. Rocket science? Bourdon tube technology? Hey you wont hurt my feelers with that stuff. The good Dr. Gauss gave us the low down on field strength. And yes the Chinese were early adopters of rocket science. So how stuff works is fun. How to fix it? I admire you who can do seats, But I ain't gonna do it. Not fun for me. Give me a good stone and I can resurface the rocker arms for you. Sounds like we could trade. Some gauge work is OK I did pull the speedo unit out and apart. The odometer was stuck and all those little wheels were fun to make work again. The numbers are still faded and I had to make my own gasket for the face but No problem. The fuel gauge has so far resisted my feeble attempts to make work. So I go on. I learn a bit and try a bit. Some work and some do not. Good news, I get to decide what is fun and what is not. Enjoy

I'm with you on what is fun and what is not. I'll try to fix anything once or twice. I cherish the successes, and soon forget the defeats.
Carl

I looked up how to repair the tube online. Watched some videos and then decided I'm too dumb to do it. Spent the $30..

We all get to that place sometime.