1991 350 tpi / when i took out the car from winter storage i noticed that the coolingfan on the passenger side turns on as soon as i turn on the ignition.
Everything is original and untouched. Ac doesnt work because it needs charge. Any ideas what could be the problem? Havent tested anything yet but will try switching too the relay that controls the fan on the drivers side. Sorry about the spelling. I am from sweden.
/ Thanks. Per

 

I think it is designed to do that when something fails, but I forget what will fail to cause that. perhaps a sensor came unplugged. maybe something to do with a/c, but just turn a/c request off at control panel, and see if it still turns on right away.

 

I have now tried switching the relays fan1 and fan 2, and turned a/c request off at control panel.i have also disconnected the switch on the condenser. The fan still runns as soon as i turn on the ignition. If i understand things right the tempsensor on the passengerside in the block also controls the fan. I will try disconnecting it when i can get the car up on the lift. How do i measure the sender? Resistans givs a certain temp i think?

 

Would be nice if someone had a picture or partnumber of the the tempswitch on the passenger side of the block.

 

I don't think that there is a temp switch or sensor in the block. There is one in the front of the intake, and one or maybe two, in the cylinder heads. You don't need a lift to get to any of them.

In some model years, a Check engine light on will trigger the ECM to command the fan on all the time.

 

It looks like this


If you can, you should order this one from hawks


You don't need a lift, just a jack and stands will do and you will see it from underneath, coming out of the cylinder head just in front of the starter

 

IIRC these work on wax melting to somehow complete the ground circut of the fan. Not sure if there is a resistor test for that. You should be able to test it by turning the ignition on so that pass fan runs, of course do this with the car cold. While it's running pull the lead off the temp switch. If the fan stops your switch is grounding all the time and is bad.

 

Thanks for your help.
/ Per

 

Solved !!
Pulled the lead off the temp switch and the fan stopped. New temp switch ordered.

/ Per

 

Nice! No jack stands needed, either, right?

Pretty sure that's the knock sensor, not a temp sensor.

 

I actually have a lift in my garage. So all i needed was the time.

 

The knock sensor is in the block and looks different than the temp sensor one I pictured.

 

I agree. But I also think that any sensor in the head is pretty easily accessible from under the hood. YMMV