[jtwoods4]

I am having the weirdest problem. My temperature gauge on my 1970 Trans Am is not working. The gauges were just restored by Auto Instruments.

I ordered and installed the correct Temperature Sending unit from Lectric Limited. I have also tested the wiring. If I stick a ground test light into the sender unit connector the Temp Gauge pegs all the way hot. So this tells me my wiring is perfectly fine.

However, when I drive the car the gauge does not move. A few weeks ago the gauge would move up to 100 but now it does not move at all.

What in the world could it be if my wiring is good, my sending unit is correct, and my gauge moves when I ground the sending unit wire? This is strange.

[rexs73gto]

When you got your sending unit did you order one for a gauge or for a light. What your saying sounds like you have a sender for a light & not a gauge. The actual gauge will act the way your describing.

[jtwoods4]

I'll double check but I'm almost positive I ordered the unit for a gauge.

[Peter Serio]

You need to do 3 things here, one testing ANY temperature gauge by ground out the green wire is not a real smart idea. This jambs up the pointer. Zero resistance )grounding the green wire) is FAR beyond any use the gauge would ever see in real life. 2) You need to test the gauge with various ohms of resistance not just "sweeping" the dial for pointer movement. If you would like to PM me I would gladly give you some ohms standards and the dial pointer position for these tests. 3rd) you should get an old, original vintage AC delco sender.

[jtwoods4]

Anyone know what the unit is to the left of the sending unit? Here is a picture.

https://www.flickr.com/x/t/0099009/p...2/13657650014/

[Greg Reid]

Looks like someone put in two temperature sending units... In fact, that's what I did on my car. I'm using an under dash gauge and decided to keep my original equipment light as well. Therefore, two sending units..one calibrated for the dash light and one for the aftermarket gauge.

[jtwoods4]

Originally Posted by Greg Reid

Looks like someone put in two temperature sending units... In fact, that's what I did on my car. I'm using an under dash gauge and decided to keep my original equipment light as well. Therefore, two sending units..one calibrated for the dash light and one for the aftermarket gauge.

I am so confused. My car has the original gauges, there is no aftermarket gauge. My car has the original wiring and the original sending units. WHY ARE THERE 2 SENDING UNITS, one on the left and one on the right. The wiring harness connects these 2 together. What the heck is going on.

[Greg Reid]

Sorry, I misunderstood your original post. Thought you had an aftermarket gauge set. I can't imagine why you'd have two temperature sending units...especially two sending units wired together. I'd unplug one just to see what happens to your gauge. .

[jtwoods4]

Originally Posted by Greg Reid

Sorry, I misunderstood your original post. Thought you had an aftermarket gauge set. I can't imagine why you'd have two temperature sending units...especially two sending units wired together. I'd unplug one just to see what happens to your gauge. .

so in the picture the correct sending unit is on the left I'm going to remove the sending unit on the right what is supposed to go in that hole? and what is the single green wire 4 if its not supposed to go on to a sending unit? I am so confused I just need to hook the temperature sending unit up correctly

["QUICK-SILVER"]

Switch on the passengers side is the thermal control switch for the vacuum timing control switch.
T.C.S. system controled vacuum to the vacuum advance when the engine was cold. It was suppose to help with emissions.
Newer models used a thermal switch with the vacuum lines plugged directly into it. Got rid of the extra electrical part.
It has no effect on temperature sending unit operation.
I think the engineers that designed it with the green wire jumping from one switch to the other....was just messing with us.

Clay

[jtwoods4]

Originally Posted by "QUICK-SILVER"

Switch on the passengers side is the thermal control switch for the vacuum timing control switch.
T.C.S. system controled vacuum to the vacuum advance when the engine was cold. It was suppose to help with emissions.
Newer models used a thermal switch with the vacuum lines plugged directly into it. Got rid of the extra electrical part.
It has no effect on temperature sending unit operation.
I think the engineers that designed it with the green wire jumping from one switch to the other....was just messing with us.

Clay

great thank you so much. so in other words the TCS temperature sensor on the passenger side has nothing to do with the temperature gauge or the temperature gauge reading and I can excluded from my testing

[Old Goat 67]

Originally Posted by Peter Serio

You need to do 3 things here, one testing ANY temperature gauge by ground out the green wire is not a real smart idea. This jambs up the pointer. Zero resistance )grounding the green wire) is FAR beyond any use the gauge would ever see in real life. 2) You need to test the gauge with various ohms of resistance not just "sweeping" the dial for pointer movement. If you would like to PM me I would gladly give you some ohms standards and the dial pointer position for these tests. 3rd) you should get an old, original vintage AC delco sender.

Do what Peter said.

[jtwoods4]

I did what Peter suggested and went to RadioShack and bought three resistors having values of 330, 100 and 50. I removed the sending unit wire and stuck one end of each resistor (one at a time of course) into the sending unit connector and the other end of the resistor to ground on the battery. according to Peter this resistance should cause the temperature gauge to move but my gauge does not move at all. the gauge goes all the way too hot if I remove the resistor and connect the wire directly to ground

[Old Goat 67]

Originally Posted by jtwoods4

The gauges were just restored by Auto Instruments.

I'd be calling them at this time.

[Greg Reid]

Originally Posted by "QUICK-SILVER"

Switch on the passengers side is the thermal control switch for the vacuum timing control switch.
T.C.S. system controled vacuum to the vacuum advance when the engine was cold. It was suppose to help with emissions.
Newer models used a thermal switch with the vacuum lines plugged directly into it. Got rid of the extra electrical part.
It has no effect on temperature sending unit operation.
I think the engineers that designed it with the green wire jumping from one switch to the other....was just messing with us.

Clay

That, I did NOT know.. The wires definitely threw me as I'd never seen that configuration before. I might have guessed if I'd seen any vacuum lines going to it but I didn't...and still don't...?
Sorry for the confusion JT...

[jtwoods4]

Well I have an update for everyone. I sent the gauges back to the restoration shop and they determined that the temp gauge calibration was way off. It may have been dropped during shipping when it was originally restored and shipped because the odometer gears were also cracked. Anyway, due to the calibration issue the gauge was not moving as the resistance of the sender decreased. The shop repaired everything and is overnight shipping back to me at no charge. Top notch
Service from the guys over at auto instruments.

Anyway, the gauges arrive in the mail tomorrow. I will post the results.

[Pepi]

Cool, at least it sounds as though you found the problem.

[jtwoods4]

Originally Posted by Pepi

Cool, at least it sounds as though you found the problem.

Yeah that was a frustrating one.