AC fan speed varies when driving

[James Kerr]

I noticed that when I drive my trac the ACs fan speed slows down when I acelerate, is this normal for these trucks? The truck is new to me.

 

[2]

From personal experience that means you have an electrical problem, in my cases it has been caused by a bad battery and another time by loose battery cable connections on the battery post.

 

[Boodrodon Dykes]

Is it heavy acceleration or normal acceleration? and does it almost cut off? does it get hot or cold? and when you let off the accel does it come back?







Boodro

 

[Gavin Allan]

What Olaf says. Check the battery cables, clean the connections, and have the battery tested.

 

[James Kerr]

The harder I accelerate the slower the fan gets, as I back off the pedel it speeds up. I've never had a vehicle do this so I was wondering if it was normal and from what you guys are saying, it isn't. I am going to check the battery and connections and if thats all good then the alternator.

 

[Mike S 3]

are you sure the fan speed is changing and not just the air flow coming out of the vents? The blend door is vacuum controlled, and obviously the more you accelerate, the less engine vacuum.. this sounds like the vacuum bulb or vacuum check valve aren't working right..

 

[Boodrodon Dykes]

Mike- That is what I was thinking it was. I have that problem myslef. but I wasnt sure if he was sure it was the fan speed or the blend door messin up.

If its air flow not coming out of vents and the little that is coming out is not cold, then its the blend door like mike said, and you have a vacuum leak.





Boodro

 

[scott degroot]

You have a vacuum leak, either a broken vacuum line to the hvac system or a bad vacuum check valve. WHat happens is that under load the vacuum bleeds off and there is not enough vacuum left in the vacuum reservoir to hold the blend doors in their proper position.

 

[James Kerr]

It does seem like its just less air coming in and yeah it does get warm in the truck while that is happening. I am going to give the vacuum system a good check up and see if I can figure out whats going on. Very informative guys, thanks.

 

[Dan Long]

If you pay attention, you'll probably notice the air coming out of the defroster vents as well. My truck tends to do this when accelerating up large hills, I just haven't gotten around to finding the vacuum leak yet.