Just installed a new thermo switch from MAM in my 87. Well it says it is supposed to be on at 200 degrees and off at 185 degrees... Not this one. Mine came on at 189 and then never shut off... It would creep back up to about 176 then down to about 170 and repeat that cycle.

Has anyone else had thermo switches that are as inaccurate as this?

How is MAM customer service? I sure hope its good, cuz I'm kinda pissed... I don't need both my fans running endlessly!

 

MA is pretty good with customer service....call them...I bet the ship you a new one for "free". Let us know how it works out.

 

Your dash temp gauge does not necessarily indicate the temperature where your thermoswitch is located, so thinking that there is something wrong with the thermoswitch is not logical.

 

But, wouldn't you think the fans would turn off at some point?

 

I bought one from a forum member(N.I.B.) and it was supposed to be on at 200, but comes on around 185. It didn't start out that way, it seems to have lowered expectations now.
It only runs my aux fan, but drives me nuts because the aux fan is somewhat noisy. I'm yanking it out and buying one from my local parts place.

 

A bwd TFS4 or a FS4 (Autozone SKU 5970644) on mineTurns on 210* to 215* off at 200*. The temp at the sensor must be diff than the gauge as it varies at diff times. Results great. That is the right temps. If it starts to climb it turns on and it is high enough it turns off.

 

Not "off" at 185 it won't. I don't think that the cooling system in stock form with a condenser installed would get down below 185 that often.

I would say your gauge is off but you can verify with some water, a pan, thermometer, stove, and multimeter if you are worried about it. I normally test switches that way prior to install to make sure that they close at the correct temp.

 

My gauge can't be off, atleast not by much, because before I put the new thermo switch in, the primary fan would kick on at about 226 and isn't that damn close to where it is supposed to come on at? It would normally turn off at about 215 I think. Now both kick on when it says 189 and they stay on forever, because it can't reach a low enough temp for them to kick off at. ( I assume that has to do with the thermostat opening and closing somewhere in that range.

There is no way they sell these thermo switches that say on at 200 and off at 185, and have them run indeffinatly...

 

Because how much heat the fan(s) can dissipate is a function of CFM, coolant capacity and radiator design. It has nothing to do with the thermostat (which is needed to keep the engine at an operating temperature that suits - among other things - longevity). If you wanted to see how well your system was designed (before adding the switch), turn on the a/c. That cranks the main fan on with a Condensor Temp of about 100 degrees (which is about 220 psi) and keeps it running until it drops to about 80 degrees (190 psi) - temps well below any thermostat (another reason it needs one) or any thermoswitch keyed to Coolant Temperature. The system is no longer under control of the Coolant Temp Sensor (which would not crank the fan on until 226 degrees). In other words, the fan is pretty much running full time (but also remains under control of the ECM which will disable it based on VSS input - something these switches lose) and whatever your gage indicates is a decent indication of what it can do until you upgrade your Fans, Cooling Capacity, Shrouding etc. Sytems that don't function within the design parameters need something more than a switch, but I don't know if that's a problem with your Vette since you say the Main was cranking at 226.

 

As long as the water temp is at or above 185* in the head between 1 and 3 cylinder the thermo switch will not shut off. It has no connection to the thermostat. When the switch is at it's high range the contacts close and ground the relay. When it drops back to the lower range it re opens the ground to the relay. If the temp in the head stays above the lower number the fan will continue to run. The primary fan should run from the computer. One fan is controlled electronically and one mechanical at least on the 89s.

 

I have them both hooked up to the thermo switch.

 

Then they both will run together and the computer will not control either. The fan will not run when the air is on or may not turn off. My advise is to put them back the way tyhey were and change the thermal switch to turn on at a lower temp. On at 215* is fine. The vette is designed to run above 185* and you should let it do so. I don't have to worry about turning on or off switches or fans running or not. I am very happy with the results.