C1 Reproduction Temperature Senders

[Richard M.]

Will follow up later but I am again pulling hairs to get one that is not 30 to 50 degrees apart from the known good gauge comparing by using IR measurements at the sender and intake sender housing. #'s 1, 2, 3, 4 are no good. Some are 20* out, some 30* out and gauge reads higher than actual. #3 is in the engine right now and ~20* high on gauge.

The chart was made measuring resistance with IR gun and my heat gun on the bench. Not perfectly accurate method but trying to see variances to select the best one. I have tried 4 of the 6 I have, and just got a Wells TU-5 at Auto Zone yesterday and trying that one today after some heat gun/ohms test. Will post results later.

What a PITA.

Rich

[Terry D.]

Re: C1 Reproduction Temperature Senders

Richard

I admire your patience to do such a test, but I believe this was done years ago on this forum, and the TU-5 was the sender of choice. I started using them right after that and have found that on three different cars, a 61 and 2 62's, using an IR gun. that they are very accurate .

Terry

[Joe R.]

Re: C1 Reproduction Temperature Senders

The temp sending units from NAPA and Others will NOT work on original gauges or REPO gauges correctly.

The following are temps and ohm readings for correct sending units.

212 degrees 140 ohms
200 175
180 210
160 265
130 380


JR

[Richard M.]

Re: C1 Reproduction Temperature Senders

Thanks Jr, I had that data some time ago but lost it.

Terry, I did research and the TU-5 was the sender of choice so I just got one.

Maybe this will work, results later.

Rich

[Jim L.]

Re: C1 Reproduction Temperature Senders

The temp sending units from NAPA and Others will NOT work on original gauges or REPO gauges correctly.

What I encountered with NAPA sending units was thermal runaway. That is, once the senders reached a certain temperature, their negative temperature coefficient caused them to self heat, which reduced their resistance, which caused even more self heating, and so on.

I could turn on the ignition but not start the already-warm engine and the temp gauge would jump up to a fairly normal reading. Then, as the ignition remained on, the gauge needle would slowly start to climb. I verified the sender was at fault by watching the Voltage at the sender gradually decrease, indicating that its resistance was going down.

[Richard M.]

Re: C1 Reproduction Temperature Senders

Interesting Jim, Thanks.

So I tested the TU-5 and my GM NOS. This time in water. My heat gun numbers are junk.

The TU5 is closer to JR's spec, but not that great. at 180* water, I get 185 ohms.

The GM NOS AC Made in U.S.A part is worse. At 180* water I get 179 ohms.

I put the TU-5 in the engine. Marks the 5th one so far. Gauge reading with IR gun comps to come later.

Rich
PS The TU-5 is not Made in USA. It's made in Mexico. Maybe it'll work better than the Asian versions as Mexico is closer to Florida.

[Jim D.]

[Ken A.]

Re: C1 Reproduction Temperature Senders

The temp sending units from NAPA and Others will NOT work on original gauges or REPO gauges correctly.

The following are temps and ohm readings for correct sending units.

212 degrees 140 ohms
200 175
180 210
160 265
130 380


JR

Joe, these don't match any thing we sell.

[Joe R.]

Re: C1 Reproduction Temperature Senders

Joe, these don't match any thing we sell.

You are the one that gave me those numbers.

Duh!!!!!!!!!!!

[John D.]

Re: C1 Reproduction Temperature Senders

I have had good luck testing TSU's using a pricey digital ohm tester left over from my building days.
Here's a few numbers for you. Dirt changes readings. Holding them in your hand is a no no. I put them on a glass top at about 68 degrees room temperature. I have checked mostly original AC Made In USA Temp senders. The last ones that were made with the very small font aka replacement AC ones go way out of range.
My chart includes auto stores and AC's.
AC's:
.74 on a 59 to 62 FI baseplate
.99 on a '62 'FI baseplate
.77 on a '62 Fi
.803 on an early '57 baseplate.
.725 on an original AC Made in USA with big letters.
1.00= Service replacement AC.

I have a NOS 63 TSU in a blue box. reads .842. Has three little squares or diamonds on each side. Bottom is recessed.

Recap: If I see in the high 70's and low 80's on customers TSU's and my own I feel they have a shot at being accurate and guess what. I only ever got one complaint. Now of the above is scientific. Just success.
Upside down letters = later AC's. I only work on '57 to '65 FI's
Jumping around.
.69 is a new NAPA. No good
.67 is a TSU5 from Beacon auto in old days
TS6 .77 from TUNG Soil. Worked excellent on a customers '63. Gauge held at 180. This was many years ago though.
Recently I took my tester to two auto stores. Not mentioning names of stores. None of the temp senders was worth squat.
My 63, the LWC has a NOS temp sender right out of the bluer box. Gauge holds dead nuts at 180 degrees.
John D.

[Ken A.]

Re: C1 Reproduction Temperature Senders

You are the one that gave me those numbers.

Duh!!!!!!!!!!!

Not me but I'll give this: 180 is 105 ohms.

[Richard M.]

Re: C1 Reproduction Temperature Senders

Hmmm,

So the TU-5 was a epic fail. Gauge reads 200 when TU-5 IR gun at base of sender is 160*.

I just let the engine heat soak a while.

Picture tells story. 159* IR gun at sender = 106 ohms. IR gun proven accurate and matches radiator thermometer I have.

Just checked at 150*. Meter reads 125 ohms.

I give up. Going to the shower, then dinner and then a movie.

[Joe L.]

Re: C1 Reproduction Temperature Senders

Interesting Jim, Thanks.

So I tested the TU-5 and my GM NOS. This time in water. My heat gun numbers are junk.

The TU5 is closer to JR's spec, but not that great. at 180* water, I get 185 ohms.

The GM NOS AC Made in U.S.A part is worse. At 180* water I get 179 ohms.

I put the TU-5 in the engine. Marks the 5th one so far. Gauge reading with IR gun comps to come later.

Rich
PS The TU-5 in not Made in USA. It's made in Mexico. Maybe it'll work better than the Asian versions as Mexico is closer to Florida.

Rich------


What is the GM part number of the NOS sender you measured?

[Richard M.]

Re: C1 Reproduction Temperature Senders

Jim D, Agree, the LL part is junk and is a 40* variance from yours. Your read 20* colder. This one 20* higher. The LL I have is Sender #4 on my chart. Reads 20* higher than IR gun. This is the first sender I installed.

John D, Thanks for your detailed post. I'll analyze it more tomorrow.

Terry, Your TU-5's and mine are quite different.

Ken, I will plan to create a resistance bridge to test the dash gauge as a baseline. I will post test results so you can tell me if it's in range or not. I really need to verify the gauge, even though I'm thinking it's fine.

Jim L, I am thinking I would rather rebuild a fuelie unit with a leaky fuel meter to high pressure pump surface than deal with this sender madness. I am approaching equal time on both diagnosis and repair. I have drained this radiator at least half of a dozen times now, maybe more, to work this issue.

JR, I recall that info from you long ago but don't remember where it came from.

Joe, It's 1513321.It's on the clear bag in blue ink in the upper right in that 1st photo in 1st post....again here. I just opened the bag for the tests as the other senders were failing. According to my data it covers 1956 to 1978 Corvette, maybe other models also.

Rich

[Darryl D.]

http://www.parts123.com/corvettecentral/partsort.pta?catalog=cadefibx&pagesize=50&page=1&year=&partno=301290