NO TEMP READING???

[dcoland70RR]

Second post about this, 70 RR 383, all new factory style gauges and wiring harnesses bumper to bumper by me over winter, factory replacement style harnesses. All worked immediately except no temp reading. I installed a new temperature sending unit at time of all new wire harnesses. Called awesome G&H California wiring company that made wire harnesses I got from YEARONE and they helped me test the entire system and temp sending unit. They are awesome because they have taught me so much over the phone diagnosing different electrical issues in my car over phone, I owe them. Anyhow, they informed me how to test the temp sending unit when car is cold then hot and no change in negative electrical reading so appears bad temp sending unit. And they helped me test the temp gauges with negative pulse to have the gauge sweep and that worked so the explained the new gauge is working properly then. Tonight new 9 dollar factory replacement temp sending unit arrived in mail, installed and ran car for long time, still no temp gauge reading. I AM STUMPED, all new gauges, all new wiring, new radiator and temp sending unit but no gauge reading. When I shut the car off I then turned ignition on and the temp gauge needled slightly like vibrated back and forth a tiny bit a few times but still maxed out to the right side of the gauge towards 0 temp reading. Any ideas?

I installed a 165 thermostat over a year ago and car runs fine. Last summer I had an aftermarket temp gauge hooked up and worked great with car always running at a great temp. Trying to put it back to new factory gauge but 0 luck. Any ideas are great?

 

[Ironbuilt]

What type of temp gauge are you using? I ask this because if you are using AutoMeter or Autogage, you need to use their sending unit. I found this out the hard way. I was having the same problem, no temp reading. After 3 different sending units, I ordered the AutoMeter and it worked. No problems since.

https://www.summitracing.com/parts/...MIz_iS1YSx2gIVAkwNCh2mowT-EAQYAiABEgLT4_D_BwE

 

[dcoland70RR]

Sorry if my last long post wasn't clear. Last year used autometer temp gauge with their attached sending unit and all worked fine. Now i have all new factory wiring and all new factory style OER gauges and temp gauge not working with all new parts tested and replaced twice

 

[moparnation74]

Sorry if my last long post wasn't clear. Last year used autometer temp gauge with their attached sending unit and all worked fine. Now i have all new factory wiring and all new factory style OER gauges and temp gauge not working with all new parts tested and replaced twice

Ground the sending unit wire and see if the gauge pegs.......

 

[Ironbuilt]

Sorry if my last long post wasn't clear. Last year used autometer temp gauge with their attached sending unit and all worked fine. Now i have all new factory wiring and all new factory style OER gauges and temp gauge not working with all new parts tested and replaced twice

Did you ground the gauge to check it? I see that you said tested, so I assume you did. Just because it's "new", doesn't mean that it's good. If the sending unit tests out and you ground the gauge and it pins it, that checks out. Check resistance between both ends of the wire to make sure there is no break. IMO, that only leaves a ground issue somewhere. I'm assuming the gauge is key hot.

 

[moparnation74]

Did you ground the gauge to check it? I see that you said tested, so I assume you did. Just because it's "new", doesn't mean that it's good. If the sending unit tests out and you ground the gauge and it pins it, that checks out. Check resistance between both ends of the wire to make sure there is no break. IMO, that only leaves a ground issue somewhere. I'm assuming the gauge is key hot.

lol....beat ya to it....

 

[moparnation74]

Sometimes the sending units do not make good contact. This is primarily due to using too much tape over the threads....

 

[Ironbuilt]

Sometimes the sending units do not make good contact. This is primarily due to using too much tape over the threads....

Which would solve the ground issue.

 

[dcoland70RR]

I appreciate posts, I am new to wiring. I called M&H and they said to ground the tmep wire (purple factory) from the engine harness and run a wire from that to the negative battery and turn ignition on. They said if gauge works properly then it will sweep all the way from left to right (maxed out temp reading) and then back to the left (0). I did that and the gauge did exactly that, swept from left to right and back to left side. They then said to test the negative reading on the temp sending unit post while motor is cold, they explained how to do that over phone and I gave them the reading. They said run car for awhile until hot and shut the car off and run the same test on the temp sending unit post and the negative reading should change slightly. I did that but the negative reading on the temp sending unit post did not change at all from cold to hot engine. They said that would mean my new temp sending unit is bad. So i just purchased a new temp sending unit, installed it but still same issue.

 

[moparnation74]

Which would solve the ground issue.

Agreed...If it pegs the gauge when grounded....I would back the temp gauge in and out a few times so it can get good contact......Before completely removing it and creating a mess....

 

[dcoland70RR]

I just saw those posts, there was white in color small amount of thread tape on both of the 2 different temp sending units I installed. So should I likely remove it all and see what happens?

 

[dcoland70RR]

Agreed...If it pegs the gauge when grounded....I would back the temp gauge in and out a few times so it can get good contact......Before completely removing it and creating a mess....

Do you mean to take the temp sending unit out and re install it? or the gauge from the dash?

 

[dadsbee]

Tape isn't anywhere in the vocabulary on my side of the aviation world! I use nothing but PST 592 on all threaded fittings, fuel, hydraulic, senders, etc and have never had a leak or a ground issue in 25+ years using it.

If you ground the sender wire and the gauge sweeps full, it can be nothing but the sender. It should have the same / similar ohm sweep as oil pressure and fuel senders. 10 ohms to 70 ohms. 70 or a bit higher cold and 10 would be boiling over. Normal op temp somewhere in the middle.

 

[Ironbuilt]

Try installing it with no thread tape and clean the threads on the motor side.

 

[moparnation74]

I just saw those posts, there was white in color small amount of thread tape on both of the 2 different temp sending units I installed. So should I likely remove it all and see what happens?

You can do that or just back out and in several times to see if you can break enough tape for a good contact....

 

[Ironbuilt]

Tape isn't anywhere in the vocabulary on my side of the aviation world! I use nothing but PST 592 on all threaded fittings, fuel, hydraulic, senders, etc and have never had a leak or a ground issue in 25+ years using it.

If you ground the sender wire and the gauge sweeps, it can be nothing but the sender. It should have the same / similar ohm sweep as oil pressure and fuel senders. 10 ohms to 70 ohms. 70 or a bit higher cold and 10 would be boiling over. Normal op temp somewhere in the middle.

I agree, it sounds like a ground issue with the sender.

 

[moparnation74]

Do you mean to take the temp sending unit out and re install it? or the gauge from the dash?

The temp sending unit and just back out a few turns and tighten and repeat this a couple times...do this a few times and see.....if that doesn't work remove it and remove the tape....

 

[dcoland70RR]

I greatly appreciate all the info everyone! GO MOPAR, I am going with my fellow brother MOPAR lover to the Mopar Nationals in August for my first time, looking forward to it 1,000,000 percent. GO MOPAR

 

[Ironbuilt]

Good luck with your gauge. Keep us posted.

 

[moparnation74]

I greatly appreciate all the info everyone! GO MOPAR, I am going with my fellow brother MOPAR lover to the Mopar Nationals in August for my first time, looking forward to it 1,000,000 percent. GO MOPAR

I will have to keep an eye out for you there.....I will be there as well....but car less, lol....just parts searching and car looking