Temp gauge Not Working

[Ardee83]

So I have done a little bit of reading, but I still cant seem to nail down the issue.

I installed a new crate 350 motor about 2 years ago. I put everything new on it that I could and that included the temp sender. The temp sender was working fine, then one day just stopped working. It just reads cold as if the truck is never heating up. I grounded the wire and it pegged all the way over to hot. So I figured it was the temp sender, ran to Napa picked up a new one. Installed it and the same exact thing, gauge still reads cold. So I again grounded the wire and same thing, pegged all the way to hot. So now I am at a loss of why it just suddenly stopped working. Any thoughts?

1983 Chevy C10 350.

[MalibuSSwagon]

I'm battling the same issue right now. I believe it's a faulty sensor or the sensor is not grounding. So I'm going to swap to a 2-wire sensor from a 1991 Suburban, so I don't have to rely on grounding the sensor to the block. Rigth now I have an autometer temp gauge hiding in my ashtray until I get a new sensor installed.

[ray_mcavoy]

I agree with MalibuSSwagon ... your test results seem to point towards a poorly grounded sending unit. A quick way to test would be to temporarily connect a jumper wire from the body of the sending unit to a good ground.

It's also possible that the store sold you an incorrect unit (might have been packaged wrong). With the gauge disconnected, hook an ohmmeter up to the sending unit. With the engine cold, you should get a fairly high reading ... around 1500 to 2000Ω or higher. As the engine warms up, the resistance should drop down to something closer to 100Ω (depending on the engine temp). If you get an open-circuit reading on the ohmmeter, you probably received a unit meant for a warning light instead of a gauge.

[Ardee83]

Would the size in the sensor threads make a difference? The crate motor accepts the 1/2" threads, which is the original one I had installed before it stopped working. The NAPA store only had the 3/8" thread so I used a bushing to make it fit the opening of the block.

[ray_mcavoy]

As long as the sending unit they sold you is meant for a gauge (not a light) and has the correct temp vs. resistance curve for your gauge, the thread size shouldn't matter.

However, there is the possibility that the added bushing is preventing the unit from making a good ground contact with the engine. Have you tried connecting a temporary ground wire to the body of the sending unit yet?

[MalibuSSwagon]

i bought an Airtex brand sensor, did not work from day 1. I suspect the sensor was just not good or I got sent the wrong one, I tried grounding the case and got nothing on the gauge. I'm going to the junkyard and grabbing a 2-wire grounded sensor, later 1991-1997 era GM cars and trucks used this gauge sensor, including the 1991 squarebody suburban. Then I know I'll be getting a good ground connection.

[midnight rambler]

I thought there are 2 sensors

[ray_mcavoy]

Originally Posted by midnight rambler

I thought there are 2 sensors

Yes, there are 2 sensors on engines with electronic feedback carburetors or electronic fuel injection. One is a coolant temperature sensor for the ECM. The other is a sending unit for the temperature gauge (or a switch for the temp warning light).

The ECM temp sensors typically have an black oval-shaped plastic socket that accepts a 2-terminal sealed Metri-Pack connector. These sensors have a dedicated ground wire and do not rely on the threads for ground. However, I don't think their temp/resistance curve is compatible with a gauge.

The gauge type sending units used all sorts of different connector styles over the years. A lot of the 90's era applications (like MalibuSSwagon mentioned) have a gray oval-shaped plastic socket that also accepts a 2-terminal sealed Metri-Pack connector ... the gray connector is keyed different than the black one so they can't get mixed up.

Also be aware that many of the 90's gauge sending units still rely on the threads for ground. Even though the connector has provisions for 2, there is often only 1 pin in the unit's socket. Some have a metal blade in the middle of the socket but that doesn't actually connect to anything inside the Metri-Pack plug.

[hatzie]

There are several different temp gauge senders for the 73-91 squarebodies. The earlier and later temp senders have a different Ohm range for the sender.

Delco PN from the 79-84 parts books... This one applies to you with your 1983.
AC Delco Part # 8993106 1/2"-14 Thread; W Gauges (Tang Connector), AIRTEX / WELLS Part # 1T1049, STANDARD MOTOR PRODUCTS Part # TS71
AC Delco Part # 8993164 3/8"-18 Thread; W Gauges (Tang Connector), AIRTEX / WELLS Part # 1T1008, STANDARD MOTOR PRODUCTS Part # TS76

For those with earlier trucks...
Delco PN form the 73-78 Parts Books
AC Delco Part # 1513321 Obsolete 1/2"-14 Thread; All W Gauges (Nail Head Connector)

The Standard Motor Products TS6, Wells 1T1053, and even AC Delco G1852 "Drop In Replacements" don't have the same Ohm range as the original AC Delco 1513321 sender. The gauge will read high or low depending on who made your incorrect sender. I used the 1981+ temp gauge guts with the 76 steel, a painted needle, and the later model sender.
Here's a thread on this board about the obsolete sender.
http://67-72chevytrucks.com/vboard/s...d.php?t=587190
Letric Limited has a replacement sender that's pretty accurate above 140F.
http://www.lectriclimited.com/electrical_devices.htm
The C1 & C2 Corvette guys have hashed the obsolete 1513321 sender over pretty good with graphs of the Ohms Vs Temp on OEM and aftermarket senders...
http://www.lbfun.com/warehouse/tech_...eCF-Thread.pdf