Temperature Sender

[Tom Hartman]

I have recently put together two cars for friends. One is a '69 SS 396 and the a '69 "Z". Both cars have consoles with gauges. The problem is both cars show they are running hot on the gaugeither car has overheated, just run up in the red on the gauge. I used aftermarket senders that have a blade terminal instead of the factory eyelet. When I changed the wire over, did I screw up the continuity in the wire? Thanks in advance, I am stumped.

Tom

I should have added, both cars are stock builds with new thermostats and clutch fans with shrouds.

[Donnie]

get the sender with the stud and nut.
I had the same problem with the push on blade type.

[budnate]

guy on ebay supposedly sells the right one, claims it will read right, I bought one but have not used it yet.

[njsteve]

This is a similar problem with the Pontiacs: all the aftermarket senders are essentially calibrated for the idiot lights even though they sell them to fit the cars with gauges. So they read waaaaaay high. I am currently hunting for the right sender for my T/A which at the moment reads 210 when it is actually 170 (checked with an actual thermometer).

Read here:

http://forums.performanceyears.com/forums/showthread.php?t=632070

This company supposedly sells a correct sender:

http://www.lectriclimited.com/mainpage.htm

[Tom Hartman]

Sound like I need a couple senders. I will order the ones on-line and let you know how they work. I thought there had to be a connection with both cars having the same problem. Thanks again for the advice and the link.

Tom

[njsteve]

Yes, please update us the minute you get one installed.

I'd love to know that someone is making the right sending unit out there, somewhere!

[Audric]

I have had the same issue with my 73 T/A, I bought from NAPA, Autozone, Checkers, and even Classic industries to no avail! Still reads like it is going to overheat. I will wait for your test on the lectriclimted!

[Steve Shauger]

Wells manufactures a replacement sender that is virtually identical to the original sans the AC and made in the US script. The part# is TU12 and they work perfect and have been using them for years. Autozone sells them and i bet that where Letriclimited procures their senders.

[Mr70]

Keep in mind too that most temperature senders are positioned in the head,so you're reading an upper head temp. & not a realistic block temp.
Head temps run much higher then the block,and are not always accurate to what is really happening.

[njsteve]

Well, I bought one of the Lectric Limited senders, installed it in the cyl head in the factory spot and it reads 25 degrees higher than the radiator water temperature measured with an accurate thermometer dipped into the coolant.

So much for the accurately calibrated reproductions. <<GRAEMLIN_URL>>/thumbsdown.gif

The explanation provided above, that the cylinder head will give a higher temp reading than the block location may be true, but that doesn't explain the accuracy of the original factory senders. Were they undercalibrated to compensate for higher cyl head temps?

[Steve Shauger]

Steve try the Wells sender I mentioned. They always read at the quarter graduation. To compare original versus new/repop you would need to verify the resistance levels at specific temps. I have both maybe I'll make a stew and check the resistance levels. If I recall correctly they call out the same sending units regardless of placementfor several years 68-72ish. Possibly the difference was in the gauge ( they may have a different voltage divider in the gauage based on placement and application. I only use the factory gauge as a ball park anyway.

[njsteve]

The Lectric Limited sender reads 63.7 ohms when the car's dash gauge says 220 degrees. (Pos lead on terminal end of sender and neg lead to threaded side of terminal, as well as to actual engine ground)

The thermometer, as well as a capillary bulb mechanical gauge immersed in the radiator at that time, both read 190 degrees.

I'll have to wait til she cools down to get additional readings.

[Mr70]

Steve
Are your thermometer &amp; capillary bulb gauge,reading coolant temperature after it's passed through the cooling fins &amp; cooled down some on the passenger side of the radiator?

[njsteve]

The coolant is flowing (thermostat is open) and the car is idling with no airflow over the fins so I don't believe that the cooling effect of the radiator would account for the 30 degree temperature discrepency. I will try mounting the actual mechanical gauge in the same cyl head spot next.

If you all recall, I had this same problem with the SW electric temp sender and gauge in my hemi Charger until I replaced it with a mechanical gauge and finally got an accurate reading.

[njsteve]

Went to Autozone and bought a TU5, which is the replacement sender for 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 &quot;correctly calibrated&quot; was nowhere near as accurate at the $6 Autozone TU5 made by Wells.

I have someone sending me an original GM 1513321 next week so I can get the readings off of that one and compare.

[mockingbird812]

Nice work &quot;Mac&quot;. Now, can you make your own sender with some string, a paper clip, and a wad of chewing gum? <<GRAEMLIN_URL>>/dunno.gif <<GRAEMLIN_URL>>/beers.gif

[L78racer]

found this info online.
http://www.lbfun.com/warehouse/tech_info...geCF-Thread.pdf (http://www.lbfun.com/warehouse/tech_info/gauges%20&amp;%20instruments/Temp-Sending-Unit-and-GaugeCF-Thread.pdf)

[njsteve]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Ls6racer</div><div class="ubbcode-body">found this info online.
http://www.lbfun.com/warehouse/tech_info...geCF-Thread.pdf (http://www.lbfun.com/warehouse/tech_info/gauges%20&amp;%20instruments/Temp-Sending-Unit-and-GaugeCF-Thread.pdf) </div></div>

Wow! Those guys make me look like like an amatuer. (Hey wait aminute, I am) <<GRAEMLIN_URL>>/grin.gif

One thing I notice is that their chart readings go the opposite way mine do ohm-wise - their resistance drops as temp rises. I'll recheck and see if I'm reading my gauge wrong - or just putting decimal points in wrong places.

[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

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 when I get that. The original ones have the part number stamped above the threads. The later GM ones have no part numbers whatsoever and seem to be a generic replacement.

[njsteve]

Just took the car out for a test drive. I hooked up the mechanical gauge in the sender location. It's about 97 degrees outside at the moment and the car ran around 190 degrees most of the trip with the A/C on full blast.

Once you sit and idle for an extended period or shut the car down, the temp really spikes (230) but I think that is due more to the sender location on Pontiacs that is right between the two exhaust port tunnels on the HO cylinder heads. So actually, the heat soak from the exhaust manifolds may play a major part in some of the high readings when there is no airflow. The heat soak may be heating the outside of the temp sender more than the coolant is heating the sender bulb inside the cyl head.

[njsteve]

OK, just got an original, vintage GM 1513321 temp sender, 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.

[Jim69Z]

Reviving this thread as my 69 with factory console gauge is reading in hot range... Purchased the wells tu12 and it has a straight pin on the end and is not threaded... Would this be correct for my application ? Thanks for any help

[enio45]

i just did this for my 69Z application, console with gauges and the wells from auto zone is right on the money.....6 bucks as well!

[SS427]

I have at least 15 Wells units in my inventory. Each one is marked with a Sharpie # (1-15) which correlates to a chart I made similar to Steve's after cooking each one on hot plate pot of antifreeze at the time of purchase. No two read alike and almost every car I restore the gauge reads much hotter than the engine actually is using an infra red and thermometer both. Wells has been the closest to OEM more than any other supplier but there is still no consistency or accuracy.

[Jim69Z]

Eddie .. Was the end threaded on the sender as the tu12 from adavance auto was not as it had a straight pin coming out so I ordered another one and it came same way... Going to try again as it keeps going to near h on gauge
Any chance that the resistor on the back of the gauge goes bad?
Thanks

[enio45]

It was threaded - the resistor can be measured for ohms....not sure what the ohm should be, but possible, however, if a resistor goes bad, the resistance usually goes high or completely open....thus a low reading.....

i got mine thru auto zone -

[DW31S]

Has anyone here (that are WAY smarter than me on the electrics and electronics) found a suitable replacement for the sending unit for an electric Sun Temp Gauge? The originals from Sun are nearly impossible to find; there is a fellow on eBay that claim he makes a replacement that works and will have identical readings. I grabbed my ankles and bought two of them because I love the Sun gauges and eventually will have them installed in both cars. As of now, I have NOT tried the "eBay" senders, so I can't speak for their operating in terms of being "correct". I'd really like to hear from anyone with knowledge on the Sun stuff.

[cwc]

Has anyone here (that are WAY smarter than me on the electrics and electronics) found a suitable replacement for the sending unit for an electric Sun Temp Gauge? The originals from Sun are nearly impossible to find; there is a fellow on eBay that claim he makes a replacement that works and will have identical readings. I grabbed my ankles and bought two of them because I love the Sun gauges and eventually will have them installed in both cars. As of now, I have NOT tried the "eBay" senders, so I can't speak for their operating in terms of being "correct". I'd really like to hear from anyone with knowledge on the Sun stuff.

A friend of mine has made me 2 senders for the sun temp gauge,I'm gonna try and get them next week and see how accurate,if they are correct.we can make several more. I am planning on offering to members at a reasonable price

[DW31S]

Wow! That is great news! I hope they work! I have another one that is supposed to be included in a set of gauges that I recently purchased. That one and the gauges are waiting at my local post office for me to pick up. I can visually compare that one to the EBAY units and see if they match. I don't have the needed equipment to check anything else.

[k92]

Mr. Hartman, did you by chance ever live around the Chicago area and own a 1970 Chevelle?