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Greeno
Dodge Dakota
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3/18/2002
11:45:53
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 Subject: A/C compressor spinning without A/C on?
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Had a question. I have a 2000 4.7L Dak. I have been hearing this compressor activating sound while driving with JUST THE HEAT on. So one morning, right after startup, checked it and found that the front part of the AC compressor pulley intermittently spins for about 2 seconds and stops. That is the sound that I have been hearing. Now, let me get this straight. I thought the a/c compressor spins only when the A/C is ON, which in turns, puts a drag on the drive belt?? Right?? So why is it turning with merely the vent on hot,with the blower motor on? IS THIS NORMAL? THanks. If not, it's going to the dealer with the warranty.
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JustRed
Dodge Dakota
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3/18/2002
12:08:09
|  RE: A/C compressor spinning without A/C on?
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Did you have just the heat on or did you have it set to defog and heat?
The salesman that sold me my Dakota told me that I had to turn the A/C on in addition to setting the knob to defog, but I've noticed that if I set the knob to defog/heat the A/C will run as you described even if I don't specifically turn it on.
As far as I know, this is normal. Every vehicle I've owned with A/C will turn it on intermittently when you have the defogger on to help dehumidify the air going towards the glass.
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Greeno
Dodge Dakota
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3/18/2002
18:27:50
| RE: A/C compressor spinning without A/C on?
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I believe I had the dual mode on but then I turned on just heat and it still did it. I will check again tommorrow.
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QUADMAN
Dodge Dakota
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3/18/2002
20:11:14
| RE: A/C compressor spinning without A/C on?
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I was told that the new generation heating systems run the compressor in all modes now to reduce humidity. That sounds really stupid to me but thats what several people I have talked to said. Are there any dodge mechanics here that could shed a lil light on this issue?
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Greeno
Dodge Dakota
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3/19/2002
09:59:31
|  RE: A/C compressor spinning without A/C on?
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Message:
CW, where are you?
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Dave
Dodge Dakota
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4/06/2002
00:40:25
| RE: A/C compressor spinning without A/C on?
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Modern AC's do indeed operate in defog/defrost mode. Small sporty cars especially are too air tight and have small ducts and fans. They move at best about 1/2 the air as my old '58 Galaxy Ford "wind tunnel" heater blower. We used to ride around with the heater on and the convertible top down in the winter snow. Newer vehicles use the air cond. and heater core with a "mixing valve" in the air path for defrost.
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Coma
GenIII
4/15/2002
17:03:29
| RE: A/C compressor spinning without A/C on?
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Just to reinforce everyone's comments, I always ride with the fan on the first click, usually the temp control in the middle(only had it two months), and the heat/defrost selection. I thought something was fishy when I saw water leaking out from underneath.
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ms760
Dodge Dakota
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4/15/2002
19:40:46
| RE: A/C compressor spinning without A/C on?
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Message:
Something fishy definitely is...
Well, smelly anyway.
Any decent technician will tell you that using heat to "dehumidify" (inrease the dewpoint spread)the incoming airflow and to heat the windshield surface itself to remove and prevent the formation of fog, condensation, on the windshield surface is dramatically quicker and tons more efficient than using the A/C for this purpose.
In addition, the heat method never looses its efficiency for this purpose whereas the A/C efficiency starts declining precipitously at about 55F until it is completely non-functional as the temperaturee reaches freezing. That's why most, even modern day, A/C systems automatically shut down at about 35F, leaving you to figure out what to do about all of that previously condensed moisture on the evaporator surfaces that will soon be coming your way.
The very best thing to do to prevent episodes of sudden and unexpected windshield fogging and the breeding of mold and barterial colonies is to remove the A/C compressor clutch relay during the winter months and otherwise use an aftermarket device to completely dry out the evaporator core shortly after you shut the vehicle down for the evening.
http://www.airsept.com/eed.html
The best answer I have recieved regarding the reasons for operating the A/C compressor below 55F when it is not needed for human comfort and its dehumidification capabilities are marginal at best was given to me by the chief engineer at Porsche AG last summer.
We continue to run the A/C compressor at those low temperatures in order to mask the horrid odor coming from the "leavings" of the mold and barterial spores growing on the evaporator surfaces. Covering the evaporator surfaces in this manner with a thin film of condensed moisture traps the bacterial "gas".
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latexsolarbif
Dodge Dakota
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6/09/2004
18:28:56
| RE: A/C compressor spinning without A/C on?
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That last post was pretty disturbing.Mold and mildew pose a great health risk in homes.What about vehicles?
What's worse;second-hand smoke or running the A/C?
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RadioMan
Dodge Dakota
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7/16/2004
13:00:10
| RE: A/C compressor spinning without A/C on?
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Message:
It's very easy to keep your A/C compressor from
*snapping* on and off all winter. Just find the
low freon cut off pressure switch. Most are
located near the fire wall on the right side of
the truck. It will be piped into the freon line.
Just pull that plug off and leave it off untill
next spring/summer. Your A/C system will *think*
it's low on R134 (freon) and won't let the system
run.
One other way to do the same as above is to
locate the compressors clutch wire. Pull that wire
and it won't run either.
Dakotas with electric raditor fans also run in
A/C mode. I have heard that even if low freon
wire is pulled, that fan will still continue to
run. Simple, pull the fuze for that fan. Your
clutch fan will be more than enough for winter
time driving.
You guys that removed your clutch fans,
*DON'T REMOVE THE FUSE FOR THE ELECTRIC FAN!!!*
I've been doing this for many years with all my
cars and trucks with no problems.
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