Vent/blower only defrosts

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Apr 12, 2004 | 07:46 PM

seeleyje

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Vent/blower only defrosts

I'm new to the forum, so go easy on me--the search mechanism didn't do me justice, so my apologies in advance if this has been previously covered. . .

My vehicle: 1999 (post October, 1998) F350, Crew, 7.3 PS

All of a sudden, my vent/AC/heater control will only "Defrost", no matter what position the selector **** is set to. I've checked fuses, switched the same-part relay fuses (didn't have spare ones), but it is apparently not fuse-related. One day I drove to work and everything was working fine; then on the way home I noticed it would only do defrost cycle and no face/feet switching.

This looks to be some sort of 'fail safe' default of a built-in electrical failure (possibly vacuum-actuated switch???), but was wondering if any of you all have seen or heard of what this traced back to? Of course it just came off of warranty 2 months ago!!!!

Thanks in advance for any guidance,

Jesse

Apr 12, 2004 | 07:53 PM

cookie88

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From: Cabot, Arkansas

Quote:

(possibly vacuum-actuated switch???), but was wondering if any of you all have seen or heard of what this traced back to?

Bingo!! Vacuum leak defaults the blower through the vents. I've seen lots of people post that the vacuum lines from their auto hubs has been the problem. Might start there.

Unless it's a two wheel drive of course. Then start with the vacuum motor on the passenger side fender.

Last edited by cookie88; Apr 12, 2004 at 07:58 PM.

Apr 12, 2004 | 08:05 PM

seeleyje

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Didn't start with a 4x4 switching issue though...

I did see some reference to a 4x4 switching problem, but I didn't have these symptoms. It still switches into 4x4 as I use it every day. I'll try to trace back starting from there...

Is there a separate (auxillary) vacuum pump or is it based simply on the engine's vacuum?

Thanx, Jesse

Apr 13, 2004 | 04:47 AM

Jerrybo66

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From: AZ.

I had the same problem. Squirrels chewed a hole in the vacuum hose. There's a separate pump.

Apr 13, 2004 | 10:43 AM

94.5turbodiesel

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From: Eastern Oregon

Sounds like a compressor to me. I have a late 94 and I would switch the vent settings and it would take several seconds to switch from defrost to floor. Changed the compressor and it works like a dream now. Good Luck.

Apr 13, 2004 | 11:57 AM

Oklahoma

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Ditto on the vacuum lines. That is one aggrevating problem. I liked the lever system, at least until wires, lever holes, etc would break. At least it was a quick fix with baling wire or paper clips.

Apr 13, 2004 | 12:52 PM

bnlange

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From: Mesa, AZ

I had the same thing happen a week ago. Turns out the vacuum lines had popped apart behind the glove box. There is a triple vacuum line that goes through a rubber connector that you can see if you open the glove box, then press on the two tabs in back to lower it out if the dash. Or you could just crawl under the dash and look for the vacuum lines.