temp sender not reading

[robg2001ls1]

I have completed my 5.3 swap in my 87 silverado but one problem im still scratching my head over is why the factory temp gague wont work. Ive already tried 2 new senders and i know i have the correct green wire from the factory harness because when i ground the wire, it pegs. Wont read though. ANy suggestions? heres a link to a video from a few months ago when i first complted the swap

87 chevy silverado shortbed 5.3 4L60e lsx start...

[jasonroman]

bump for info for this guy

[rayfinseats]

Sender is for idiot light? Gauge broken? I have a 90 that read 230 plus and the gauge was bad.

[robg2001ls1]

anyone?

[westie 666]

I have the same problem

you have to use the sender from your old engin as it matches the guage

[hatzie]

As stated above... You need a gauge sender for the 1987 CK.

Assuming you have the right sender...

Did you use Teflon tape on the sender threads?
Teflon tape can electrically insulate the sender threads and keep the body of the sender from grounding. New temp sensors only have thread sealer on the top 1/3 of the threads leaving the bottom 2/3 bare.

JIC you're interested. The temp sender is a thermistor (thermal variable resistor). You can check the resistance with a radiator thermometer and a multimeter set to 20K ohm range.

Attached is a table of the 81-90 CK RV temp gauge sender resistance vs temp.



Image is not mine. It's from this thread. http://67-72chevytrucks.com/vboard/s...d.php?t=461255

[robg2001ls1]

well i ended up trying a different sender that a friend brought me. He said it came with some parts he had bought but had no idea what it came from. It does read but not correctly. I had my cpu hooked up to hp tuners a few days back and it seemed the gague was around 30 deg off(showing cooler). Ive narrowed my problem down to the wrong sender. What is the correct part number or can someone post a pic or link of the one i should be running. The autozone one they gave me does not read(tried 2 already)

[gchemist]

Is the block aluminum? If so use another or better ground.

[robg2001ls1]

right now i have it tapped into the water pump

[rfmaster]

Need to fix broken header bolts - leaks introduce extra oxygen into exhaust stream which will effect close loop operation.

Regarding the temp sender not reading. Call your local Radio Shack ask them if they have 5K-Ohm Potentiometers, Model: 271-1714 (~$4).
There are three leads on a potentiometer. Get some test clip leads and connect center tab to green wire that goes to your gauge and one of the two outside tab terminals to a good chassis ground.
Turn ignition on and vary potentiometer shaft position - you should see your temperature gauge move. Now once you confirm that your gauge moves then correct temp sending unit can be extrapolated from potentiometer resistance values. For example - adjust potentiometer to read 210 deg F. Disconnect potentiometer from the truck test circuit and measure resistance between the two previously connected tabs. Repeat this for various temperature readings as indicted by your dash gauge. Put it in a table. In general, low temperatures correspond to high resistance sensor values while hot temperatures have low resistance values. Finding a corresponding sensor can be a PITA since there are no officially published parameter tables for temp gauge sending units. There is some DIY effort to characterize commonly used temp gauge sensors.

//RF