Temp Gage Not Working

[Richard R.]

1972 Small block temp gage does not register. I installed a new sending (driver side single wire) unit and temp gage from Paragon. Any suggestions on were to start trouble shooting?

[Don L.]

Re: Temp Gage Not Working

You didn't wrap the threads with teflon tape, or otherwise seal the threads to avoid leaks did you?

[Chris S.]

Re: Temp Gage Not Working

don does this keep the current from going to ground? what do you suggest on the sealing part? Or use nothing at all? I have kinda the same issue with my 57 guage, i know the gauge works as i can get it to peg with a test light. I used teflon sealer not the tape.

[Richard R.]

Re: Temp Gage Not Working

Don
I didn't put any tape or sealant on the threads. All Other gages and electrical componets work fine.

[Stephen L.]

Re: Temp Gage Not Working

Richard, Some troubleshooting suggestions....
1. Measure resistance of sending unit. Should be about 700 ohms with room temp engine. (Some temp switches look like a sender and you may have the incorrect unit. These will show very high ohms [open])

2. Using a 500 ohm resistor, install it in place of the sending unit using clip leads. If you get a reading on the gauge then your problem is with the sender.

3. If no reading on gauge then:
A. Insure gauge has a good ground on gauge case.
B. Test continuity of wiring from sender to gauge.

[Jack H.]

Re: Temp Gage Not Working

1. Measure resistance of sending unit. Should be about 700 ohms with room temp engine. (Some temp switches look like a sender and you may have the incorrect unit. These will show very high ohms [open])

2. Using a 500 ohm resistor, install it in place of the sending unit using clip leads. If you get a reading on the gauge then your problem is with the sender.

If you're going to substitute a fixed resistor, why use a value that has more meaning? 500 ohms will mimic a VERY cold engine situation with little gauge point needle movement.

A 60 ohm resistor should equal 230F on the money (GM temp sender spec) and provide a greater, more visible, gauge excursion...

3. If no reading on gauge then:
A. Insure gauge has a good ground on gauge case.
B. Test continuity of wiring from sender to gauge.

3A and 3B are EXCELLENT suggestions!

[Richard R.]

Re: Temp Gage Not Working

I can't get the temp gage to move past about 110. Continuity from sending unit to gage is good, Pink wire to gage has power, ground is good. I then used another sending unit and gage and get the same results.

I then took a third sending unit put it in not water (195) hook up a gage wiht jumper wires , independant of the wire harnes and got the saame 110 reading. Nay further ideas for resolving the problem?

Rich

[Edward J.]

Re: Temp Gage Not Working

Rich, if you have a ohm meter, you'll want to check the wire from sender to the gage itself, to make sure there ia not a connection problem or break in wire there should be little resistance, hopefully the gage cluster is out. I think the only connection between the sender and gage is the one at the firewall.another thing I've done is use a test lamp grounded then touch he sender wire and with the resistance across the bulb filiament it should make the gage move.this test can be done at the firewall connection and the gage itself.

If the gage was working recently and now its not, there could be a problem with gage.

[Timothy B.]

Re: Temp Gage Not Working

Richard,

Follow Jacks suggestions, get a 60 ohm resistor and use it in place of the sender. The guage should be right on 230*, this will tell you if the guage and wiring is accurate.

Radio shack is where I purchased the 60 ohm resistor, I went through this same thing a few weeks ago.

[Richard R.]

Re: Temp Gage Not Working

Tim & Jack

I tested the resistance in the green wire and it read .000 so that should eliminate that problem. the new sending unit in the car reads .979 ohms and the old sending unit reads .879 ohms at 60* in the garage, higher then the 700. Is that a problem?
With 60 ohm resistor in place of the sending unit it still only go's up to 110* Does that mean the new gage is bad?

thanks for your help.

Rich

[John H.]

Re: Temp Gage Not Working

Richard -

Quick check of the gauge:

With the key on, remove the connector from the sending unit - the gauge should peg to full COLD. Then ground the terminal in the connector to the engine - the gauge should peg to full HOT.

[Richard R.]

Re: Temp Gage Not Working

Gage go's to full zero when the sending unit is disconnected and only go's to 215* when it is grounded. Does that mean the gage is bad?

[Richard R.]

Re: Temp Gage Not Working

When you attach the connector to the gage does the green wire(sending unit) go on the top terminal, black ground on center and pink on the bottom? Opposite the ground is a unused terminal. Does this sound correct?

[Edward J.]

Re: Temp Gage Not Working

Rich, you are correct with the wiring, how about if you go directly to the green wire at the gage and see what happens if you ground it directly at the gage itself.if the same results you've found the problem.(Gage)

This step will by-pass the harness to the engine compartment.

[Timothy B.]

Re: Temp Gage Not Working

Richard,

You may want to locate that sender wire in the firewall plug and clean the terminal. Sounds to me like there is resistance there.