[njsteve]

On a whim I went to Autozone and bought a Wells brand #TU5, which is the replacement sender with the slide-on terminal. I tested it against the mechanical gauge and the dash gauge. Here are the results when the car was warmed up and driven four miles. (ohm readings made by touching pos lead to terminal end and neg lead to outer casing of sender unit):

TU5: when the engine was cold and the ambient temp was 80 degrees, the factory dash gauge read 0. At this time the ohm reading was 000.548. Once the car was warmed up and driven 4 miles, and a mechanical gauge capillary unit was immersed in the radiator coolant, the mechanical gauge read 160 degrees. At the same time the dash gauge also read 160 degrees. The ohm reading at that time was 135.500.

When the Lectric Limited model 01513321 was at 80 degrees ambient temp and the engine was cold, the dash gauge also read 0 and the ohm reading was 000.549. When the car was warmed up, driven 4 miles, and the mechanical gauge read 160 degrees, the dash gauge read 215 degrees and the ohm reading was 348.000.

As you can see, the $25 Lectric Limited sender that is sold as "correctly calibrated" was nowhere near as accurate at the $6 Autozone TU5 made by Wells.

I have 70RAIII sending me an original used, GM 1513321 next week so I can get the readings off of that one and compare. (I'll most likely end up using that one in the car, just to be truly correct)

[70RAlll]

Originally Posted by old goat racer

How 'bout this NOS one

Steve-
this is two of the 3 NOS units I mentioned to you I had. SOPme guy was selling these on Ebay a year of so ago, must have found a bunch of them in an old dealership. I have one additional in an original box.. ANyway, my friend is sending the original nail head model and I will have you the unit by mid this comming week. FWIW>.. this friend of mine found 6 of these temp senders used. He was about to throw them away!! He thought with repo's available no one would want them !!. Iff anyone needs one, PM me and I will help you get one..

[Old Goat Racer]

Originally Posted by njsteve

Yup. Thats the correct one but depending upon the year of manufacture it could be the later "one sender fits all" model.

I've had a few of these for 20+ years. How can one tell when they were made?

[Norwood]

So Steve with all that , you are saying the AutoZone unit read correct?

[njsteve]

Yes.

So, this morning I kicked the wife out of the kitchen and did a little experimentation on the stove with a pot of water, a candy thermometer and a digital ohmmeter. Here are the results:

80 degrees: Wells at 650 ohms, LL at 573 ohms
90 degrees: Wells at 526 ohms, LL at 445 ohms
100 degrees: Wells at 429 ohms, LL at 365 ohms
110 degrees: Wells at 328 ohms, LL at 266 ohms
120 degrees: Wells at 283 ohms, LL at 227 ohms
130 degrees: Wells at 250 ohms, LL at 200 ohms
140 degrees: Wells at 216 ohms, LL at 170 ohms
150 degrees: Wells at 198 ohms, LL at 155 ohms
160 degrees: Wells at 173 ohms, LL at 133 ohms
170 degrees: Wells at 157 ohms, LL at 119 ohms
180 degrees: Wells at 135 ohms, LL at 101 ohms
190 degrees: Wells at 120 ohms, LL at 89 ohms
200 degrees: Wells at 109 ohms, LL at 79 ohms
212 degrees: Wells at 104 ohms, LL at 75 ohms

So, from the tests above, the Lectric Limited sender has a resistance level far different than the Wells sender.

And as a result of my weekend TempSender-Palooza, I am going with the Wells sender as the one that makes my temp gauge far more accurate when it comes to reading what the coolant temperature actually is, as corroborated by an actual thermometer as well as a mechanical temp gauge. (That is, until the original GM unit arrives)

I will update with the original GM sender data when I get that.

[CaptCrunch]

Originally Posted by njsteve

OK, I kicked the wife out of the kitchen and did a little experimentation on the stove with a pot of water, a candy thermometer and a digital ohmmeter. Here are the results:

80 degrees: Wells at 650 ohms, LL at 573 ohms
90 degrees: Wells at 526 ohms, LL at 445 ohms
100 degrees: Wells at 429 ohms, LL at 365 ohms
110 degrees: Wells at 328 ohms, LL at 266 ohms
120 degrees: Wells at 283 ohms, LL at 227 ohms
130 degrees: Wells at 250 ohms, LL at 200 ohms
140 degrees: Wells at 216 ohms, LL at 170 ohms
150 degrees: Wells at 198 ohms, LL at 155 ohms
160 degrees: Wells at 173 ohms, LL at 133 ohms
170 degrees: Wells at 157 ohms, LL at 119 ohms
180 degrees: Wells at 135 ohms, LL at 101 ohms
190 degrees: Wells at 120 ohms, LL at 89 ohms
200 degrees: Wells at 109 ohms, LL at 79 ohms
212 degrees: Wells at 104 ohms, LL at 75 ohms

So, from the tests above, the Lectric Limited sender has a resistance level far different than the Wells sender.

And as a result of my weekend TempSender-Palooza, I am going with the Wells sender as the one that makes my temp gauge far more accurate when it comes to reading what the coolant temperature actually is, when compared to an actual thermometer as well as a mechanical temp gauge. (That is, until the original GM unit arrives)

I will update with the original GM sender data when I get that.

THANKS!

[njsteve]

Originally Posted by old goat racer

I've had a few of these for 20+ years. How can one tell when they were made?

I think the good early ones have the part number stamped above the threads versus the newer GM ones that don't have anything there.

[317th FMS]

If you google "1513321 GM" and click on that first PDF file there is alot of good info on this. I tried to add to the thread but it was too big a file.

[njsteve]

Yes. that one is:

http://www.lbfun.com/warehouse/tech_...eCF-Thread.pdf

It has some ohm spec charts for a variety of senders. It's a Corvette forum and they also talk about the problem with the newer GM senders. They also have some good photos of the senders as well.

By the way I just took the T/A out for a test drive with the mechanical gauge installed in the temp sender location. It's around 97 degrees outside at the moment and the car ran 190 most of the way with the A/C on full blast. It did heat up a bit (the car that is) once I stopped to assist the well-dressed, damsel in distress on the side of the road who was looking for a graduation party somewhere in the area and had no clue about what road it was on.

And of course on the return trip it seemed that everyone in the area who had a lawnmower, was out trimming their gravel as I tried to drive by.

[CaptCrunch]

Originally Posted by njsteve

Yes. that one is:

http://www.lbfun.com/warehouse/tech_...eCF-Thread.pdf

It has some ohm spec charts for a variety of senders. It's a Corvette forum and they also talk about the problem with the newer GM senders. They also have some good photos of the senders as well.

By the way I just took the T/A out for a test drive with the mechanical gauge installed in the temp sender location. It's around 97 degrees outside at the moment and the car ran 190 most of the way with the A/C on full blast. It did heat up a bit (the car that is) once I stopped to assist the well-dressed, damsel in distress on the side of the road who was looking for a graduation party somewhere in the area and had no clue about what road it was on.

And of course on the return trip it seemed that everyone in the area who had a lawnmower, was out trimming their gravel as I tried to drive by.

Are you running an original 4 row radiator?

[Old Goat Racer]

Mine just say AC Made in USA 12 Volt

[njsteve]

Originally Posted by CaptCrunch

Are you running an original 4 row radiator?

The 72's used a three-core. I'd love to put a four-core in it like I did with my Grandmother's 75 Firebird (original owner car). That car now won't break 165 degrees on a 100 degree day with the a/c going. But since the T/A has its original four-speed radiator (the one with no auto trans cooler fittings), I kept that one in the car after having it recored. The local radiator guy said due to the width limitations of the original tanks, there was no way to convert it to a four-core unit. Maybe after I get the car judged I may buy a four core and save the original but for now, I'll stick with what I got.

[Pepi]

So Steve, are you or did you get some resistors, and put them in series to get some of your resistance readings, and hook it up to your gauge, to see which resistance reads correctly on the gauge, the Wells or LL?

[njsteve]

Originally Posted by Pepi

So Steve, are you or did you get some resistors, and put them in series to get some of your resistance readings, and hook it up to your gauge, to see which resistance reads correctly on the gauge, the Wells or LL?

No. The readings I got were simply the raw ohm resistance data I got by using the ohm meter at the various temperatures while the senders were sitting in a pot of water on the stove, with the water level up to the top of the threads. I'd get to a certain temp, shut the burner off, let the temp stabilize, take the readings and then turn the heat on to reach the next higher temp, 10 degrees at a time.

The resistor-adding theory they were discussing in that article related to trying to make the gauge read correctly instead of finding the correct temp sender that gave the correct signal to the gauge in the first place. The downside to adding resistors was that the gauge would only be accurate at one temperature, not through the entire range.

I'm no electrical engineer like some of those guys in that article, but I think finding the right sender would be the logical solution.

[CaptCrunch]

Originally Posted by njsteve

The 72's used a three-core. I'd love to put a four-core in it like I did with my Grandmother's 75 Firebird (original owner car). That car now won't break 165 degrees on a 100 degree day with the a/c going. But since the T/A has its original four-speed radiator (the one with no auto trans cooler fittings), I kept that one in the car after having it recored. The local radiator guy said due to the width limitations of the original tanks, there was no way to convert it to a four-core unit. Maybe after I get the car judged I may buy a four core and save the original but for now, I'll stick with what I got.

In my younger years I managed a large radiator shop. You could have a custom core made to fit your original tanks that would help some.........I copped out and put an Alumitech radiator in my formula......wouldn't look right for a car as original looking as yours but not bad for an after market aluminum radiator.....a three row is going to be marginal at best.......I didn't know they used 3 rows on 455's.........

[njsteve]

Hey, it's all Al Gore's fault anyway, for all this global warming hoopla!

It wasn't this warm in NJ back in the 70's when these cars were new!

:-)

[Transamric]

I think some of the confusion on this part is due, in part, to the fact that GM changed the name of the part, as well as the part number down through the years. In the 1970 PDM, sheet 480841 #2, the part is called a Transducer Assembly, #1513321, with option U30.
The 9/1/70 Pontiac MPC has it as #1513321 also, but calls it a thermostatic gauge switch (round single conn.) (w/rally gauges or aux. gauges). But the part does not function as a switch. A switch is all on or off, make or break. A gauge sending unit is a thermistor, giving a varying reading. Thermistor or transducer is more accurate.
But switch would be an accurate description of a sender for an idiot light, since they simply trip to close the circuit & turn on a light.
Sooooooooo,...all this is to say that when you use an idiot light sender in a car equipped with a gauge, the gauge will read no temp, until the sender (switch) reaches its' pre-set temp at which it will trip & make an internal connection. (Often around 248 degrees) Then the gauge will quickly go up to near max reading.

[Formulabruce]

I agree with transamric, however, we need to look at a couple things
1. Steve that link to article is for a small block Corvette, look at the picture at the bottom with the teflon tape mythbuster!!
3. That said, the resistance in the GM sending units for guages was made to work where there was alot of heat sink, IE water around it in the top of the intake. I ran a 71 with guages and it always seemed hot, tried new senders, even letric, and similar results, then I moved the sender to the the intake for yuks, and put an infrared gun on it and bam it worked well, and correct'
4. These units for switching on an idiot light from the head, or turning on fans in newer cars work fine and head temp ALWAYS leads engine temp, unless ya own a 3rd gen LT-1. That said, I have never been able to nail down the guages correctly even with new GM sensors way back in 78 when my neighbor brought his pontiac over.
5. Conclusion, the senders from letric work perfect for 70-73 cars factory guages if you put the sender in the intake, by the thermostat, ( spark unit location on some)
I looked for a spec on the actual debth for the sensors of=r the actual length of them, and actually used a small extender in the head once, which I thought would be good but it heats up and no way to cool the metal, not enough water. Finally I firmly believe that GM had in mind using these in the intake for readings, look at their design, they are so close to hot metal near only 2 cylinder in a head .
If you get a sender for guages to read that your engine is at 180, and the sender is in the head, your probably running at a dynamic ( t stat open) temp of 160 . The thermostat is designed to control engine temp, makes logical sense to read the temp there.. I battled this on non chevy,GMC stuff for a bunch of years
PS not trying to stomp on any toes here....

[njsteve]

OK, just got the original, vintage 1513321 temp sender from 70RAIII, here is the updated chart:

80 degrees: Wells at 650 ohms, LL at 573 ohms, GM at 549
90 degrees: Wells at 526 ohms, LL at 445 ohms, GM at 524
100 degrees: Wells at 429 ohms, LL at 365 ohms, GM at 409
110 degrees: Wells at 328 ohms, LL at 266 ohms, GM at 365
120 degrees: Wells at 283 ohms, LL at 227 ohms, GM at 323
130 degrees: Wells at 250 ohms, LL at 200 ohms, GM at 272
140 degrees: Wells at 216 ohms, LL at 170 ohms, GM at 227
150 degrees: Wells at 198 ohms, LL at 155 ohms, GM at 195
160 degrees: Wells at 173 ohms, LL at 133 ohms, GM at 175
170 degrees: Wells at 157 ohms, LL at 119 ohms, GM at 157
180 degrees: Wells at 135 ohms, LL at 101 ohms, GM at 140
190 degrees: Wells at 120 ohms, LL at 89 ohms, GM at 125
200 degrees: Wells at 109 ohms, LL at 79 ohms, GM at 109
212 degrees: Wells at 104 ohms, LL at 75 ohms, GM at 102

Looks like the Wells sender is pretty darn close to the original GM sender's specs. I'd say it's a dead-on match given my pot of hot water on the stove, scientific method.

[Formulabruce]

Steve, so if you put it in the head, and your gauge reads correct, what is the actual engine temp at the T stat with an IR gun? does it match???