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AC/Heater Blower during acceleration

I have a question about the AC/Heater Blower operation on a 96 Dodge Ram.

During acceleration while running either the AC or heat when I accelerate the AC or Heat exhaust is diverted from the dash to the defrost vents.

Now, I never noticed this occuring before but started happening after Dodge replaced the MAP sensor on my truck.

My question is can the replacement of the MAP sensor cause this or during the replacement they buggered up some vacuum lines?

Also, I know there is a TSB, 24-01-96, which talks about the same problem I'm having but it just seems like too much of a coincidence that it occured after the MAP sensor was replaced.

I plan on going down to the dealership tomorrow and speak to them, so any assistance would be appreciated.

Thanks, Mark

Reply to
mmaral
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I've had lots of cars that do something like this under full throttle. Typically, a spring holds the HVAC dampers in one position and vacuum in other positions. At full throttle, the vacuum drops dramatically often letting the spring win the tug of war. I'm guessing that in your truck the spring holds the damper in the defrost position and vacuum pulls it to allow air through the other outlets.

I can't imagine replacement of the MAP sensor affecting this, but I don't know the vacuum schematic for a Ram so I can't comment. I just know that this general behavior isn't unusual. Also, many vehicles will kick off the AC compressor when under heavy throttle. It isn't unusual to lose AC temporarily when climbing a long hill.

Matt

Reply to
Matthew S. Whiting

Based on my experience on a Reliant with a similar problem, I would say there's a vacuum leak which is putting the steady-state vacuum at a level just barely enough to operate the defrost/vent controls normally, then, when you accelerate the vacuum drops below that marginal threshold.

Yeah - I'd look for a small vacuum leak.

Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")

Reply to
Bill Putney

My Jeep Comanche did this often. We have grades here in PA that run for multiple miles. The reservoir wouldn't hold out. The dealer installed a second reservoir under warranty. That pretty much fixed it, but there was still one grade, about 5 miles long, that I had to run at full throttle with the old 2.5L 4 banger. After about 3 miles, I'd see the HVAC system making uncommanded changes in setting...

Matt

Reply to
Matthew S. Whiting

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