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ac will turn to heat and back to ac
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lesmcguinn
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Jan 8, 2013, 3:34 PM
Post #1 of 10
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ac will turn to heat and back to ac
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2001 dodge ram truck
5.2 v8 engine
My ac runs pretty good for an old truck but this past summer it started acting up. When I hit the brakes the ac will turn to high heat. Hit the gas and it slowly goes back to ac. Turn the unit off/on it will quickly go to ac. The temperature control knob is also very ineffective. Either cold or hot no in-between even in the heat mode. I have tried to find any vacuum leaks but everything looks ok. Any ideas?
Thanks,
Les McGuinn
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Hammer Time
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Jan 8, 2013, 3:58 PM
Post #2 of 10
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Re: ac will turn to heat and back to ac
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Somebody is going to have to put gauges on it and monitor exactly what is happening during this failure.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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lesmcguinn
New User
Jan 14, 2013, 1:24 PM
Post #3 of 10
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Re: ac will turn to heat and back to ac
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Hammertime,
Could there be a problem with the vacuum solenoid under the dash? How would one test this part?
Les
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Hammer Time
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Jan 14, 2013, 2:19 PM
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Re: ac will turn to heat and back to ac
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OK, don't listen then.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
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Jan 15, 2013, 2:58 AM
Post #5 of 10
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Re: ac will turn to heat and back to ac
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Hitting brakes does cause a quick loss of vacuum confusing the system. Manifold vacuum is a measure of what a variety of things should do so for the moment see if vacuum booster is not leaking or a problem with it then proceed,
T
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Hammer Time
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Jan 15, 2013, 4:06 AM
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Re: ac will turn to heat and back to ac
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Vacuum has no relationship to temperature in that vehicle.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
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Jan 15, 2013, 5:57 AM
Post #7 of 10
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Re: ac will turn to heat and back to ac
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Hitting the braked did however they are boosted there's the clue FIRST!
T
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Discretesignals
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Jan 15, 2013, 6:05 AM
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Re: ac will turn to heat and back to ac
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HT is right that you should check AC pressures to see if the ac clutch is being kicked off during this episode.
Another consideration that comes up is the inability to control the heater blend door. Could the blend door be broken or not connected to the blend door actuator causing the door to swivel on its own during acceleration and deceleration?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Tom Greenleaf
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Jan 15, 2013, 6:25 AM
Post #9 of 10
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Re: ac will turn to heat and back to ac
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Be interesting to see if this behaviour could be duplicated while sitting there or only while driving along. Long A/C hoses and gauges under a wiper trick or what?
So much is hard to know without witnessing it. It might be on the cusp of a stall and A/C cuts out. Dunno - perhaps just the surge of weight towards the front while braking - all things normal wouldn't do anything but something is wrong related to braking or so it seems??
T
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Hammer Time
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Jan 15, 2013, 9:23 AM
Post #10 of 10
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Re: ac will turn to heat and back to ac
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It very well could be just a low RPM cutout but until somebody watches what the compressor and pressures do, we will never know.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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