This is where my temp gauge reads on a hot summer day after driving for 20 minutes. Thoughts? Defective sender? What temp corresponds with each mark on the gauge?

 

What's a "hot summer day" on PA? Here in Florida its' 92 and 20 minutes later mine is reading just about 200. Yours looks like about 160? Do you have a 160 thermostat in there?

 

STOP and look at your gauge really good. Starting at '220' ...which is at the 12 o'clock position....ad heading towards the 280 mark. Look a the amount of distance that it takes to reach 280 degrees....AND...if you go back towards the 100 degree mark. IT IS the same amount of distance from the 220 mark. BUT....from 220 to 280 is ONLY 60 degrees. But from 100 to 220 it is 120 degrees.

SO...worrying about what temp is the mark that you needle is showing is (my opinion) not important. Even if you were slightly to the left of the 220 mark..I would not bat an eye.

The reason is this...when you temp sending is being heated up by the coolant...it sends a ground signal to the gauge...and depending on how much resistance the temp sender sends.....the gauge will respond accordingly. And what I do know from talking with my gauge restorer...the value of ground resistance when the sender is being heated up...does not necessarily increase in a linear scale.

I focus on running /operating temperatures which for me is 200 degrees. If it goes to 210 while sitting at idle I do not freak out...as long as it goes down when going down the road.

If I have customer that is concerned like you are. I remove the temp sender and install my racing temp gauge and run it and record the temp so I can let them know basically that when the gauge is at that position...their tempo is 'X'. I also use my infra red thermometer also.

DUB

 

Below are the expected resistance inputs for the 1979 temperature gauge. Based on other gauge expected readings I'd say your actual temperature is between 190 and 200. The issue is GM never published the temperatures at the hash marks in detail. So all I have to go on is readings and ohms from another year gauge.

Your needle indicates that your sender is sending out aprox. 119 ohms.. If I take that ohm reading to another gauge for say.. a 1980 103 ohms = 200 degrees... and since you are above that I'd say you'r just below and nothing to worry about IMHO.

-Willcox




Here is the same gauge for a 1980.

 

I would suspect that your thermostat has been changed to a 160*F stat (should be a 195*F stat from factory)... Or your factory stat has failed in the 'open' position. If it takes quite a while for the water temp to come up to temp, my bet is a defective stat.

 

Thanks Willcox!

Just goes to prove that the ohms when it is at 100 degrees and when it is at the hottest point on the gauge...the half way point in the gauge face temperature reading is NOT half of the amount of ohms from 100 to full hot.

DUB

 

my fiero was missing the stat and took forever to even get up to correct for it according to gm temp....in that car if it runs too cool the comp richens the mix and well.....

 

Exactly.. Temperature gauges are not a linear scale like fuel and oil pressure... they are all over the place.

Years ago we used NOS gauges and tested them for the required input so that we would have a correct fixed scale for calibration. Call it dumb luck or call it curiosity but it's paid dividends in the end knowing.

We have a input scale for every gauge that we've used for years when we rebuild the gauges.... It's paid off for everyone in the long run.

Ernie

 

You'll need to fake it out Bats... lol.. GM screwed up the sender outputs years ago... The issue in a fiero is that it's reading the output from the sender which is going to be hard to manipulate. The best thing you could do is try to find an original sender.... then cut it open and repair it. I did a write up on how to do this on my repair page years ago. We chuck the sender in a lathe and cut the top out of it. Senders fail because they loose their oil. When the oil is gone anything between the thermister and the top connection corrodes... so the basic thought is to open up the top, clean everything, fill with oil and epoxy everything back together.

You can review this pictorial at this link: http://repairs.willcoxcorvette.com/?...erature+sender Or by reviewing this thread on the forum. https://www.corvetteforum.com/forums...post1591842458

Ernie