Temp. sending unit

[Jim D.]

My temp. gauge in my 1960 has always read low. I know the sending unit is a well known trouble source. I was wondering if anyone has tried the one available from Lectric Limited? They state "correct resistance and connection, produces accurate gauge display" in their catalog. Do they really?

Jim

[Jack H.]

Re: Temp. sending unit

Some of this lies in the eyes of the beholder... The factory original spec for the AC 1513321 temp sender is a variable in terms of accuracy.

The accuracy is VERY tight at the top end of the dial (engine about to overheat...needle going into the red zone), while it gets progressively more sloppy as temperature decreases. I suspect that's why there are few gradicules on the temp gauge's face plate...

Most complain because they expect highly accurate readings at the gauge's mid-scale (around 180F) and that simply wasn't the case. Even a temp sender in 'perfect' compliance with factory specs can range +/- 10F in the middle of the dial.

The system was apparently intended to replace the existing 'idiot light' AND give the driver a sense of 'drift' (relative magnitude and direction of coolant temperature change). But, we're used to today's modern cars and somehow want to force an accuracy level into the technology of the 50's and 60's that simply wasn't there to start with...

[Jim D.]

Re: Temp. sending unit

Thanks for the reply Jack. The problem is, that at operating temp. (180 degrees confirmed with an IR gun) my gauge reads barely above 100. I've tried other sending units that almost bury the gauge to the hot side under the same circumstances. I'd be happy with one that is accurate at 180 and to he11 with the other readings. That's why asked about the one from Lectric Limited.

[Stewart A.]

Re: Temp. sending unit

Jim, I have the opposite problem. The IR gun reads 160 and the needle is 210 -220. That scares me. I just got an original sender off Richard Thomas and I will be trying that very soon. I"m figuring that if it reads to low I'm going to take the pod out and get it re-calibrated with correct sender. Jim you could always just drive the Cobra. Stewy

[Jack H.]

Re: Temp. sending unit

Now that's a decent thought! Most simply concentrate on the temp sender and BANG away trying to find one that makes their guage read properly. They forget it 'takes two to tango' and overall accuracy is also an attribute of the gauge itself...

The early temp gauges were calibrated by having a test operator connect the assembled gauge to a 'ding ding' box that provided fixed voltage and current characteristics applicable to an emerging engine overheat condition. Then, the calibration test operator installed the pointer needle onto the guage shaft to make it read properly (+/- a few degrees).

Later gauges were assembled with the pointer needle installed, pointing to the cold end of the dial. The finished gauge was attached to a final calibration machine and the operator picked from a selection of precision, wire wound, resistors to install a 'shunt' that would force the gauge's pointer needle to correctly indicate the appropriate high temp condition.

Most presume their guage HAS to be good and go about changing temp senders to get a proper reading at the gauge's MID scale... So, starting the debug process by questioning the calibration of the gauge itself is a healthy, intelligent approach!

[Dennis A.]

Re: Temp. sending unit

Jim...
Try a Tu-5 Wells Temperature sender from Autozone. Most accurate that I have found...

[Jim D.]

Re: Temp. sending unit

Thanks for the replies everyone. Dennis, I'll try to hunt one down this week-end.

Jim

[Jim D.]

Re: Temp. sending unit

Jim you could always just drive the Cobra. Stewy

Stewy, The gauge in the Cobra never goes above 90 degrees. I always forget they all read in Celsius.

Jim

[Hank D.]

Re: Temp. sending unit

I second the motion on the Wells TU-5 from Autozone. Fixed the problem on my 1960.

[Mark P.]

Re: Temp. sending unit

Should these senders always be installed without any teflon or any other thread sealant ? I was told teflon and other sealants could cause an inaccurate reading. Is that true ?

[John H.]

Re: Temp. sending unit

Should these senders always be installed without any teflon or any other thread sealant ? I was told teflon and other sealants could cause an inaccurate reading. Is that true ?

Mark -

Not really. The pipe threads are razor-sharp, and will cut through any sealant in order to provide an adequate ground; even if the ground is less than perfect, it will cause the gauge to read LOWER, not higher.

[Stewart A.]

Re: Temp. sending unit

I was going to say the same thing Jack. But I thought I would let you say it. Stewy

[Jim D.]

Re: Temp. sending unit

I just picked up the Wells TU-5. I like the $6 vs. the $25 from the other place. I'll give it a try. Thanks to all.

Jim

[Stewart A.]

Re: Temp. sending unit

Chev's don't get hot, Windsors get hot, must be the worst motor in the world for overheating. Best boat anchor in the world.
Yeah teflon should do the trick don't sender units take the reading from the bottom bar.
Stewy