I am currently working on the ac system and have most components removed...this includes having the high pressure, low pressure and cycling switches unplugged as well as the wire harness attached to the evap box. Now the fan stays on all the time (this is an 85 MPFI) and the check engine light comes on sometimes when stopped or moving slow and then goes out again (haven't had time to check for the code yet).

Any idea why this stuff is happening??

 

I remember reading somewhere that when you remove the A/C you have to jumper two wires. Do a search on A/C removal and you should be able to find it. About half way down in this post is what you are looking for. https://www.thirdgen.org/forums/tech...FC+removal+fan

 

Ah ha, thanks! THe high pressure cutout switch is open which is kicking the fan on. I will have to jump it until things go back in.

Any idea why a code would be thrown though?

 

Sorry, no clue on the code. Check it and maybe I can offer some help. I assume you already know that you can check it without any special tools.

 

Yeah, just haven't had a chance yet. Just thought it might be an obvious issue so I thought i'd ask anyway. I will check this morning.

 

Did you get to check codes yet?

 

Yeah, it was the MAT sensor. I guess it wasn't plugged in all the way? But the fan doesn't run all the time now!

thanks.