Thread: how to test electric fan?

Just did a motor swap on 02 gtp. The donor engine was a 98. My a/c and electric fans worked before the swap. They are a no go after start up with donor motor. a/c has power no cold though. I would like to think these two things are related but cant be sure. I think i have all my grounds right and plugs in. I have no warning lights or other problems. Maybe a faulty sensor? Temp. sensor or something?

To test the fans should i use a test light or multimeter? Where do i use the meter to see if it has power? Stick it in the open fan plug? If so which hole or wire color in the plug? Or do i test the relay slot? Will i get a reading with just the key turned forward?
In testing the a/c compressor pretty much the same questions as testing the fan.

When testing relays i just jump the relay with a paper clip? I think there was 3 fan relays. Which should i paper clip or should i try each one? When i jump the relay will the fan come on automatically when i turn the key forward?

Originally Posted by Scottydoggs

id swap the temp sensor with the one that was in your dead engine.

That got the electric fans going. a/c still a no go.

Have you checked ALL the fuses- meaning the underhood and in-car ones?

The a/c worked before the swap. The a/c light will come on when you push it. There just isnt any cold air coming out of it. The fans work now though.
I checked the fuses under the hood. I havent checked any relays.

CHeck the refrigerant pressure in the a/c system. Did the car sit an extended period of time when changing the engine? A/c systems are know for leaking refrigerant when sitting unused for extended periods of time, sometimes all that is needed is some refrigerant.

Have you checked all grounds?

The car did sit for about a year.7 months with the old engine still hooked up and about 4 months with engine out of the engine bay. a/c lines were never unhooked.

Im not sure how many grounds there are. i know that there is 3 on a bellhousing bolt.

The a/c just blows warm air and doesnt ever think about being cold with max a/c and full fan.