84, fan is operated by a temp switch, passenger head btwn 6 & 8.

Car came to us with dead engine from overheat.

As im about to drop a resealed donar engine in, i have been checking everything i can to discover root cause of overheat. Furthermore the car had a manual override for the fan operation. So, proper cooling system operation is suspect.

Hence testing rad fan switch.

i read the switch, if factory, which it appears, grounds the switch on the relay when temps reach 230f (110c)

I could not get my boiling water to surpass 95c. I could never reach continuity btwn the blade and the threads/sensor body. OK, needs to be hotter. So i never verified it was capable of creating the ON signal/ground.

But here is my question….

I switched to resistance, i watched as the ohms increased as it cooled. in real time.

Why would it do that? Id think this should be either ON or OFF. As i watched the resistance increase with every second that passed as it cooled….i wonder if maybe a PO bought a “coolant sensor” and inadvertently installed the wrong one for the job. The tested switch appears to behave like a temperature sending unit. Changing resistances with fluctuation in temps.


Will an ON /OFF switch have a scaled resistance?

Thnx, VT.

 

It's changing resistance because, that is the type of sender that goes in the LH head (between #1 & #3 cyliders) for the temperature gauge in the dash. The sender for the fan, should have the "mushroom" style, single pin connector (like a knock sensor). Standard Parts TS-136, is the sender I recommended to you, when you guy's first got the car....I still strongly believe you'll be much happier with it, than sticking with the stock one👍

 

Heat gun might able to get it to the temp you want!

 

The fan switch should be on/off. Wrong switch used. To get water to boil at a hotter temperature, add salt.

 

Only slightly. It takes about 60 grams of salt/lt of water to raise the boiling point .5° C. Negligible really. Only way to raise the boiling temperature is to pressurize the vessel. At the OP's altitude, he is only getting about 206° F. from boiling water.

 

A GM# 3040674 or an after-market equivalent and of course in your case you'll need the correct connector. The 3040674 in Standard doesn't change to the mentioned in #2 but I do believe I've seen that mentioned previously.

 

Thnx Everyone.

Yes, the pressure where i live is lower due to my altitude. Takes less heat heat to boil as a result.

But yak’s suggestion of a heatgun worked.

Im not sure if the blade style that changes resistance that came out of the head was the correct one or not. but i did learn, after using a map torch, that the resistance drops from in the high hundreds of ohms once heated. at exactly 50ohms, the circuit is COMPLETED and exactly 51 the circuit is opened again. Given my harness looks factory, id say this is the factory “switch”. That said, due to the inaccuracy of the flame method i couldnt nail down the actual temp it grounded at. only the ohms. the laser would read 30d difference if inmoved it even a tad. I *think* the 50ohms was around 120c. Too high.

Furthermore, I have learned that proper temp switches turn ON, and stay on even below the ON temp. So the fan can draw the temp down below the ON temp. Whereas this switch that i tested, is on/off at 50ohms like a light switch.

I couldnt get the ts136. I did get a ts147 from my lps. The issue is that nobody posts what the on off temps values are. certainly nobody posts what the resistance levels are in relation to temps.

Either way, i have my lps sourcing a ts 136. It will arrive eventually. In the meantime i’ll head back to my daughters Frostbite 84 thread and keep rolling. Looking to get the valvetrain in tonight 👍

As always thank you for the help! I will come back to this thread to update on what eventually works.

 

I boil them in coolant instead of water when I test them. You can get the temp way higher that way. Cooking oil works really well too? This is how I scaled the software for my oil temp sensor in my oil pan.