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HVAC Blower slows down when climbing low/high rpm


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Recently I did some "repairs" to my 89 MJs HVAC system, new Blower + resistor, bunch of other crap. I've been experiencing a phenomenon that I don't remember pre-HVAC repairs where the Blower slows to an almost stop when I'm accelerating up a hill and the RPMs are high, once I get to the top and shift, the blower speeds back up.

 

The problem is I almost never notice it untill it speeds back up so I'm not positive on the conditions which it occurs. I just know I notice it more when climbing hills.

 

Could this be a battery problem? I was thinking vaccum at first but there isn't any lines in the blower that I can recall so that doesn't make sense.

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Recently I did some "repairs" to my 89 MJs HVAC system, new Blower + resistor, bunch of other crap. I've been experiencing a phenomenon that I don't remember pre-HVAC repairs where the Blower slows to an almost stop when I'm accelerating up a hill and the RPMs are high, once I get to the top and shift, the blower speeds back up.

 

The problem is I almost never notice it untill it speeds back up so I'm not positive on the conditions which it occurs. I just know I notice it more when climbing hills.

 

Could this be a battery problem? I was thinking vaccum at first but there isn't any lines in the blower that I can recall so that doesn't make sense.

Following... Same issue on my '89, except I think the blower may remain blowing the same, but switches to defrost, which changes the sound. Almost 100% positive we're both dealing with a vaccum issue.

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It's probably doing what Hippie66 is talking about. It's probably not actually slowing the blower down, it's just losing vacuum and blowing through the defrost vents. Next time it does it feel for air coming out of the top of the dash. If air starts coming from the defrost vents, you've got a vacuum leak somewhere between the engine and the HVAC system. A good place to start would be the vacuum container behind the bumper. Trace the line coming from it for any damage, and make sure the vacuum line is pushed into it all the way. There's also a connector near the blower motor on the firewall that you might have accidentally bumped when changing the blower.

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Following... Same issue on my '89, except I think the blower may remain blowing the same, but switches to defrost, which changes the sound. Almost 100% positive we're both dealing with a vaccum issue.

Interesting. Is the defrost always quieter than the heater? Mine is almost the exact same sound.

 

You guys were right though, the defrost starts blowing when I'm climbing. My reservoir thing in the bumper isn't screwed in anymore so it's been bouncing around for awhile - I'll have to take it out and give it a once over.

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