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-   -   No AC Upon Excelleration (http://www.ramforumz.com/showthread.php?t=116835)

ramalamadingdong 07-11-2012 12:46 AM

No AC Upon Excelleration
 
1996
360cid
140000 miles

Truck was parked for seven years. Began driving it again two years ago but never checked AC until two weeks ago and no cold air. Had it serviced then left on a 1000 mile trip and noticed that the cold would stop blowing when engine was under pressure such as going uphill. Otherwise is blows very cold.

Any ideas?

moparornocar72 07-14-2012 06:06 PM

I would check the tightness or looseness of the belt and go from there.

ArtNJr 07-14-2012 06:39 PM

Quote:

Originally Posted by ramalamadingdong (Post 839080)
1996
360cid
140000 miles

Truck was parked for seven years. Began driving it again two years ago but never checked AC until two weeks ago and no cold air. Had it serviced then left on a 1000 mile trip and noticed that the cold would stop blowing when engine was under pressure such as going uphill. Otherwise is blows very cold.

Any ideas?

No doubt there is some sensor that's turning the A/C compressor off when the engine's under load, but I couldn't tell you specifically what on that vehicle. But for example, when I went to an A/C mechanics seminar years ago they chose a Ford Escort as an example car -- if you put auto trans fluid in the power steering pump (which was always the standard) instead of newer, lighter PS fluid, the A/C would never get cold. The car's engine had so little torque that it couldn't run the PS pump under load & the A/C compressor both, so when you'd make a tight turn into a parking space, etc., a sensor in the PS pump would trigger the A/C compressor to shut off & putting heavier fluid in the PS unit made that sensor detect a higher load all the time.

And newer A/C compressors are not designed to run all the time, they're supposed to turn on & off periodically. But I'd bet there's a load-sensing device somewhere that "tells" the A/C compressor to turn off when the engine's under a heavier load -- if you could get a factory service manual you could probably find out where it is too.

spillage 07-15-2012 10:33 PM

I think bad oxygen sensors on the cat can give this issue.

greendodge 08-08-2012 04:11 PM

There is a sensor somewhere that tells the a/c compressor to turn off under load. My 1997 Ram does the same thing and my parents 1991 Caravan and a friends 1995 Ram does it also. I have tried to find what sensor it is and disconnect it. You can hear whatever it is in the dash when it shuts down the compressor, sounds similar to a vacumm leak clicking on and off. If someone knows how to disable this I would be much obliged.

ramalamadingdong 08-08-2012 08:43 PM

I just returned from a 1000 mile trip and drove through some rain in Wyoming and thought that I would turn off the AC and use the cool outside air instead. I found that it was not an AC problem but a fan problem! The fan shut down upon acceleration!

ramalamadingdong 08-09-2012 10:20 AM

I just returned from a 1000 trip and while driving through a cool rain in Wyoming, I turned off the AC but left on the fan. The fan itself was shutting down upon acceleration. Sorry about the mistake!

Okiespaniels 08-14-2012 08:53 AM

Is the fan shutting down...or does the air stop coming out of the vents? My guess is the vents stop blowing but the fan runs.

There are no low pressure sensors, high speed turnoffs or that on your 2nd gen. I'm not even sure how O2 sensors figure in!

What you mot likely have is a phenomenon called "wild vents". This is caused by cracked or loose vacum hoses on your HVAC unit, damaged check valves, bad blend door motor or any combination thereoff. Usually it's the first two.

You may or may not experience a power loss from a vacum leak, but if you haven't noticed that, it's probably on the HVAC side of the vacum because there is a one way check valve on the vac distribution tree for the HVAC system. That tree is on the pass side up near the firewall. That's where I'd start. Then...start feeling around the HVAC unit near the top LH side close the the transmission hump. There's a couple of vacum actuators there. Sometimes the hoses get popped off or they break.

Google "Dodge Ram wild vents" and you'll get a bunch of helpful and more techinical bits.


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