So I got the AC up & running like a champ, now the heater/AC fan is acting up. I did a search, but need some input from you gurus to help troubleshoot this thing before & spend $$$.

OK, after I start the car (87 300D 124) & turn on the AC, I put the fan on high to start cooling. Fan runs OK for about 10 seconds & then reverts to another speed (other than HI). I change fan settings to Auto, but fan selects a slower speed (than was on HI). I select LOW, no air flow from vents. I accellerate. fan changes speed or shuts down. I stop, fan changes speed or shuts down. I turn left or right, fan changes speed or shuts down. All of this is while operating fan from the MAX position. In any other position, the fan just shuts down completely. Then it will turn itself back on again, but not at MAX fan. Hit a bump in the road, fan changes or shuts down. Sit in the driveway letting engine idle, fan changes speeds or shuts down. It's getting to be a real pain in the a$$...

I've read that this could be caused by four things: bad ground on fan;
bad control element; bad fan motor; bad connections in CCU (broken solder joints).

Any suggestions from you guys? I'd really like some input before I start throwing parts at this.

Thanks in advance!

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1987 300DT
2002 Ford F-250 7.3 Crew Cab Short Bed

The fan works and it doesn't sound like you're going through fuses, so to me, that would eliminate the blower motor itself. Not sure if a ground could work itself loose, but that's just me. I would point my finger at the CCU itself, broken or cold solders.

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That's what I am hoping it is. At least it is something that is relatively easy to fix. Fuses are all OK.

It's funny that all this started after I got the system up & running properly. Don't know if it has anything to do with it or not...

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1987 300DT
2002 Ford F-250 7.3 Crew Cab Short Bed

Doubtful, one day everything works, the next something may fail, no warning. A/C, door locks, CCU to name a few I've encountered.

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83 SD

84 CD