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Discussion Starter #1
Ok, after an exhaustive search of the forums today I haven't been able to locate the source of my problem.

The secondary electric fan isn't coming on when the A/C is on. THe compressor is engaging and running like it should, truck doesn't overheat either. When it's really hot the a/c doesn't blow cold air but works like a champ at night, low humidity etc. days.

The fan works as I hot wired it to the battery last night to make sure it wasn't burned up or whatever and it spun like it should. Checked fuses in the cab and everything looked good there. Are there any other fuses etc. I need to look for and where are they? ALSO, when I unplugged the fan from the stock harness the compressor wouldn't come on at all, plugged it back in and voila compressor works again but still no fan.

Any ideas?
thanks
m
 

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I posted a nice long reply, but it was for the 2nd gens. I'm not sure if the same applies to the 1st gen, but here goes anyway.

Ok, after an exhaustive search of the forums today I haven't been able to locate the source of my problem.


The secondary electric fan isn't coming on when the A/C is on. THe compressor is engaging and running like it should, truck doesn't overheat either. When it's really hot the a/c doesn't blow cold air but works like a champ at night, low humidity etc. days.

The fan works as I hot wired it to the battery last night to make sure it wasn't burned up or whatever and it spun like it should. Checked fuses in the cab and everything looked good there. Are there any other fuses etc. I need to look for and where are they? ALSO, when I unplugged the fan from the stock harness the compressor wouldn't come on at all, plugged it back in and voila compressor works again but still no fan.

Any ideas?
thanks
m
According to the FSM, the electric fan will only kick on under certain conditions. With AC off the temp has to be above 208 and your speed under25 mph for the fan to turn on low. Over 221 degrees the fan should switch to high. With the AC on the refrigerant pressure needs to be 229.1 psi or higher for a different scheme to be in effect. If these conditions exist then the fan should run at low regardless of speed or temp. Above 221 degrees it should switch to high again. I haven't found any information on the pressure or how to determine it while driving.

If yours isn't working then one of the two relays may be shot. There is one relay that turns the fan on low. A second relay activates with the first to put the fan into high. Unfortunatley, it doesn't look like the relays are user replacable, they are part of the IPDM (intelligent power distribution module) tucked in between the engine compartment fuse box and the firewall.
 

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Discussion Starter #3
Thanks for the input. Not knowing a thing about the 2nd gen I am not sure but it makes sense that if the compressor doesn't have enough freon in it (pressure wise) the relay for the fan wouldn't trip even though the compressor is coming on. That's my assumption not knowing where the pressure has to be to flip the compressor clutch, but I'd imagine it's a lot less than the fan relay.

Basically my neighbor (a/c tech) said he would look at it for me this weekend. He said if the fan's not on it won't work as it should. He seemed to think it was a fan issue exclusively but this information will help my case with him.

If anyone else has any suggestions please let me know and I'll post back up the results after the weekend.
m
 

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have somebody with ac experience check it first. it sounds more like low on freon. the fan needs to see hi pressure before it turns on. also double check the hi pressure hose they like to leak over time.
 

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have you read up on the thermo amp? its under your glove box and will cause your ac to not blow cold all of the time...
 

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If anyone else has any suggestions please let me know and I'll post back up the results after the weekend.
m
disconnect the high pressure switch and see if the fan comes on. The switch is in one of the lines.
 
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