My 91 S-10 Blazer with 4.3L engine has been having temp guage issues.

The problem seems to be that the guage indicates too low right now.

My original problem a couple years ago seemed to be that the temp guage was stuck on low usually only during really cold winter months.

I replaced the thermostate, anti freeze, temperature sending unit and the guage still indicated low and now seemed more of a mechanical issue with the guage so I decided to try the guage.

I got a guage from the junk yard and put it in the existing instrument cluster.

The problem seemed to improve and the guage indicated but always seemed to be low still.

After 2 years I decided to try and fix it again. I picked up 2 complete instrument clusters and a couple of more temp guages from the junk yard to try a couple out. After I decided that one of the instrument clusters seemed to work best I put that one in and buttoned everything up.

The guage seems to still indicate low after running the truck about 15 miles at 50-60 mph.

My question is this.
Does anyone know the wiring connections involved from the connector on the sending unit (green wire 1 pin) to the connector that the instrument cluster plugs in to?

That way I can check the resistance of the sending unit and check it at the instrument cluster to see if the readings are the same and I am not picking up some resistance in the circuit somewhere which will cause the guage to read lower.

I have 3 spare complete insturment panels now and extra guages if someone needs one I will sell them cheap.

Thanks.

 

Have you tested the continuity from the sender to the gauges?

The wire from the sender goes through connectors C100 (above/behind the brake booster under the hood) and C200 (I believe this is a large square connector located under the passenger side dash).

The chart below is a somewhat standard resistance chart that almost all GM temperature sensors followed:

 

You are not going to beleive this crap. After having this problem for about two years, trying two other instrument panels, I spent about 4 hours checking all the wiring and everything else yesterday.

I just decided to finally say the heck with it and try another sending unit. I went to the auto store to get a new sending unit, thermostat, and antifreeze but the didn't have the sender in stock. I picked up the thermostat and antifreeze to start with that.

I drained the antifreeze and pulled the thermostat and IT WAS STUCK FULL OPEN.

The brand new thermostat I put in at the beginning of this problem was bad and that is why the temp guage was reading so low.

Man, a bunch of troubleshooting for a stupid fix! Who would ever think that a brand new thermostat would lock open.

Thanks for the restistance listing chart I will print it and keep it in my reference book.