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-   -   AC stops blowing at certain RPMs (http://www.ramforumz.com/showthread.php?t=80087)

ARMedNBangin 04-15-2011 08:13 AM

AC stops blowing at certain RPMs
 
As said in the title, sometimes the AC stops blowing out of the vents when I hit a certain rpm. At first I thought it was just between 60-65 mph, but I goosed the gas in lower gears and noticed it was doing the same thing at other speeds. You can still hear the blower doing it's thing, but when it hits that magic rpm number, the air starts blowing out somewhere else...(haven't really tried to figure out where it was going--other vents, just up in the dash, etc.) Then after it shifts gears and the rpms change, or if you let up off the gas, the air will start blowing back outta the vents I selected.

Is this a common problem? Something to be worried about?? Easy fix?

Ideas, suggestions:

letsjet 04-15-2011 05:59 PM

I had the exact same problem on a 1999 intense blue 1500 4 x 2 5.7 auto. The dealer could'nt fix it, only seemed to do it when the outside air temperature was really, really hot. Could be a loose vacuum line to the vent. Good luck, it's a pisser to lose the a/c if it's only for a minute or two.

ArmyofOne 04-16-2011 09:44 PM

Are you sure the air stops blowing completely? Because I know your truck (and most cars nowadays) have whats called a WOT (Wide Open Throttle) cutoff switch, when your accelerator is pushed passed (in most vehicles) 50%, the ac compressor shuts down to allow extra power, it then kicks back on below 50% throttle. During the off time, the temperature of the air coming from the vents changes to ambient. It can feel sometimes like the air has stopped blowing but it hasnt. Could this be your issue?

ARMedNBangin 04-17-2011 10:14 AM

You can still hear the blower spinning...but when you put your hands to the vents that blow on your face, NOTHING comes out...not even hot air. As soon as the gears shift, or I let off the gas just a hair, the blower's noise does not stop or deviate any, but the cold air immediately returns to blowing out of those vents again. It's as though a valve of sorts is opening allowing the air to move elsewhere. Perhaps my WOT is the problem. If it's supposed to be working like it is, then that's cool. But if it's something that's wrong and can be fixed, I'd rather get it taken care of. Summer days here in South Louisiana can be brutal.

If it's a common occurance, or something that is SUPPOSED to be happening, I sure wish other people with similar stories would chime in and set me straight.

A vaccuum line? Somewhere down the line, i've heard of this problem. I don't know where I heard it from, but as I was making this initial post, that was in the back of my head--remembering a similar problem happening to a friend or colleague in the recent past and it ended up being a loose vaccuum line.

ArmyofOne 04-18-2011 11:38 AM

Ok, so you either have a vacuum line off/broken or a vacuum leak elsewhere. The air is not supposed to stop coming out, just change temps.

If your motor is still going with no air from the vents, that air is going somewhere. Vacuum leak is the next logical step.

RamTech 04-18-2011 11:49 AM

It's a bad vacuum check valve in the line leading to the interior of the truck.

xlstreetglide 04-26-2011 05:23 PM

So I've replaced both check valves now my air is coming out the defrost vents. What gives. Did I put them in wrong?

ARMedNBangin 04-26-2011 06:27 PM

Randy, where exactly is it located?

And on a scale from 1-10, how difficult of a fix will that be? I can change an alternator, change brake pads, etc, but I'm not completely mechanically inclined.

Cost of replacement valve??

xlstreetglide 04-26-2011 08:11 PM

Quote:

Originally Posted by ARMedNBangin (Post 511475)
Randy, where exactly is it located?

And on a scale from 1-10, how difficult of a fix will that be? I can change an alternator, change brake pads, etc, but I'm not completely mechanically inclined.

Cost of replacement valve??

Passenger side firewall and by intake.

1 being easy

4.00ea from dealer. Local auto parts don't carry them. Part#4549209

ARMedNBangin 04-28-2011 11:03 AM

aw hell, you've just boosted my confidence. Easy, $4 fix. That's what I'm talking about. I've gotta get it from a local Dodge dealer? Do you know of an online source for purchasing the part?


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