Tested the new fan before i installed, worked. Long story short, my old fan took a dump on me, so i ordered new one. So i put it in and ran the ac, which if working correctly the fan should run right? No go. Need to know where to start as far as diagnosing the problem?

 

It should run when the ac is running. Youre sure the AC is indeed running? The compressor is running right? If it is low on refrigerant...neither will come on. Now let the engine run for a while until the engine gets warm enough to need the fan to run. Both fans should kick on. If it doesnt...then I would remove the wire...and turn the AC on again, check for 12V at the plug. If you have 12V then I would suspect the fan again. I would then run 12V directly to the fan...see if it works.

 

I know the fan works because i ran 12 volts to it to make sure. I just need to know if the ac is on should the fan automatically kick on. Or if it makes a difference on whether its got refrigerant in it or not. If it doesnt matter, then i can check the plug for 12 v with my meter. Thanks. BTW the compressor is working.

 

It runs at the same time the other fan runs any time the key is on. Period. End of story.

If not then you either have a wiring issue or the fan timer is bad, assuming the fan itself works.

 

If the AC system is not working (low on charge, other issues) then the FANS will not come on when the ac is turned on. So if the charge is low in the AC system - neither fan will run.

Key on, remove the connector from thermo a on the t-stat housing (where the lower hose connects) and use a piece of wire to jump the wire side of the connector. BOTH fans should run.

To "holmes" point - anytime the key is "on" and the conditions are right, BOTH fans run. The only time ONE fan would run (3rd thru early 6th gens) is when the key is off.