Temperature sender values

[acme66]

I have a failing trans temperature sender. You could have made some diamonds if you had coal when I looked down half way up the grade and saw the trany temp north of 260. After some testing I have been able to determine that my sender failed at set percentage off true value, like a out of whack speedometer. It is closest when the truck is cold and spreads as it heats up. Seems to be about 15% off so 260 was about 220. Anyway I now have a table of resistance values that might prove useful for someone trying to tell if they have a hot motor/trans or a bad sender unit.

The following "good" numbers are based off of my engine temp sender which is absolutely dead spot on. The two senders are identical so the readings will work for either the motor or the transmission. The sender for the transmission is on top through the trap door on the return line. The sender for the engine is in the water manifold, right hand side towards the front. Pull the plug off, measure from the pin of the sender to a good ground.

Set you meter to the 20,000 ohms scale to match mine.
Resistance on cold motor, air temp around 70F -4.10 (41,000 ohms)
Resistance on motor @130F -1.46 (14,600 ohms)
Resistance on motor @150F -1.2 (12,000 ohms)

The bad sender readings respectively were:
5.23 cold, 2.4 @ 120F, 1.5 @ 150F

This all assumes my gauges are good but they seem fine. Maybe someone will find this useful. Simple enough thing now to check your own if you have a known good baseline to work from. I never checked to see if there was a thread on this and if there is maybe a mod could blend them.

Ken

 

[Csm Davis]

Thanks for this should be very helpful but really need a reading at 190 on engine and and one at maximum normal transmission temperature so that if you are pretty sure the truck is not over heating but at normal operating temperature you could check the sender and know if it is the problem as it usually is.