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Skyewalker
Dodge Dakota
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8/01/2002
00:40:49
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 Subject: a/c cool to hot
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Just bought a 2000 Dak Sport 4x4 ext cab. I notice that when I turn the air on, it comes on cool as long as I'm driving. When I come to a stop or put it in park, the air turns warmer, then cools down again once I start driving again. I took it in to the dealer twice and they said "nothing wrong, no leaks". Not sure what it could be. Any thoughts? Thanks!
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Mark P.
Dodge Dakota
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8/01/2002
07:56:51
|  RE: a/c cool to hot
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The amount of cooling from the ac is dependant on engine RPM. When you come to a stop, the RPM's go down and the compressor speed slows, which reduces the cooling. While parked, increase and hold the RPM. You should notice that the air gets colder.
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handi2
GenIII
8/01/2002
08:36:54
| RE: a/c cool to hot
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The air conditioner should be cooling the same at any rpm's. There is something wrong, take it back and show them. Let them sit in it with you and let them sweat.
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WallyR
Dodge Dakota
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8/01/2002
09:36:57
| RE: a/c cool to hot
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Mark, you're right on this one. Compressor RPM is directly related to the refrigerant mass flow rate in the system.
The problem with all 2000 and before ANs, DNs and BRs in the lack of condenser capacity, especially at idle. All of us with an 02 truck have the hybrid electric fan on the backside of the radiator-makes a HUGE difference-so much that I've removed the viscous fan and have no cooling problems and only minor A/C degradation at idle and that's in Texas of all hot places. Picked up a few HP as well.
I recommend adding an electric fan and going to a different dealer for a second opinion to make sure the charge amount is correct.
Wally
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Buggy-Bumpers
Dodge Dakota
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8/01/2002
12:36:50
|  RE: a/c cool to hot
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He's right about the electric fans on the 2001 and newer Dak's, however all of the AC's will get a little warmer when you stop because you have less air flow coming thru the cooling coils which is what cools the refrigerant so that it may cool the air in your truck. While sitting at a light after coming to a stop put hte truck in Neutral and run the refs up on the engine and see if it starts to get a little cooler. Another thing is to check to see what the actual temperature is coming out of the vents, the AC is only designed to drop the outside temperature by a set temperature. If all else fails take it to an another shop that specializes in AC's and see what they say and if they don't agree with dealer then have them give you acomplete writup of the problem and fixes that are required then take it back to the dealer and make them fix it if it's under warrenty.
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Dodster
Dodge Dakota
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8/01/2002
12:47:29
| RE: a/c cool to hot
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My truck is a 2000 4.7 that came w/ electric and viscous fan. I removed the viscous fan to gain the hp. The electric fan comes on when engine temp reaches 210 or when ac is turned on. I haven't noticed any diff when the engine is idling or under a load. Skyewalker's situation does not seem normal. I would have it checked out.
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SS_Dakota
Dodge Dakota
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8/01/2002
12:48:27
| RE: a/c cool to hot
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Mine is perfectly fine at idle... no warm air coming outta that puppy. Try gettting the AC recharged... mine is a 2000 3.9 FYI
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WallyR
Dodge Dakota
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8/01/2002
13:03:57
| RE: a/c cool to hot
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Something else-the 1994 Rams were so bad that the owners manual actually instructed the driver to "place it in neutral and rev the engine to 1500 RPM should you experience discomfort in stop and go traffic".
Wally
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frigidcool
Dodge Dakota
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8/01/2002
14:56:30
| RE: a/c cool to hot
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The Sanden 5 cycl compressor is not the most efficient compressor at low speeds. The best at that was the old RV-2 from days gone by.
Realize too that the AN series daks do NOT use an expansion valve nor and EPR valve to regulate flow of refiregerant to and from the evaporator. Daks simply use a fixed orifice tube design (very similar to refrigerators, home AC, Central AC, freezers) and this design is totally dependent on the rate of flow of refrigerant. Slow down the engine RPM and the AC compressor RPM decreases also.
In home units a fixed orifice tube or capilary line is ok because the compressor operates at a constant speed give or take depending on line voltage. In a motor vehicle, the compressor speed obviously varies according to driving conditions.
One thing to check is the condensor for debris. Its is clogged with dead bugs, etc? Even if it looks clean, some 409 and a hose will be a good idea. Also, verify the operation of the Fan clutch. DOes the speed of the fan increase when the airflow temp heats up or does it "freewheel"? The electric fan is an auxillary device to move air; system is designed to allow for the engine fan to move the air.
Finally, did the dealer actually hook up some gauges and run performance check? Or did they, like most dealers, simply rev up the engine andsay this is fine and dandy? See if you can connect with a person who has AC gauges and also try to find a service manual where you can see the specs of high side and low side operating pressures.
One indication of low refrigerant is rapid cycling of the compressor clutch. Does yours do this? how long does it stay engaged? Is the "off" cycle too long? (Bad heat switch or EVAP temp sensor or receiver might be loaded with debris or excess moisture. Again, a proper test using gauges will help pinpoint where the problem lies.
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WallyR
Dodge Dakota
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8/01/2002
15:32:21
| RE: a/c cool to hot
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FYI frigidcool,
Sanden hasn't sold an SD-5 compressor to DCX since the 79-81 L body with the VW engine. All newer compressors (piston type) are the 7 cylinder models. These comps have dual gapless piston rings which vastly improve volumetric efficiency. Add to that an increase in displacement and the SD-7 is superior to the 5. I have one on my truck and since DCX has finally addressed the system deficiencies the idle performance is outstanding. With these vehicles the problems were design related, 1) as you said they are CCOT and 2) no condenser performance at idle. The older vehicles would cycle constantly on the high side HPCO at any ambient above high nineties.
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pimpdaddy don
Mechanic
8/01/2002
16:46:07
|  RE: a/c cool to hot
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yo, buggy-bumpers is fully correct. i have been in the air conditioning field for the last 6 and a half years, and thats exactly whats happening. the only other possibility for it to work better would be to charge with a little more than factory freon, and get an aftermarket mini-cooling fan, hooked up to a toggle switch so you could turn it on and off as you wish to keep it cooler in heavy traffic and whatnot.
Donny
http://www.dodgetruckworld.com/mygallery.asp?id=3361
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frigidcool
Dodge Dakota
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8/01/2002
16:54:46
| RE: a/c cool to hot
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I stand correted. Thank you wally for the clarification.
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Skyewalker
Dodge Dakota
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8/02/2002
00:30:36
| RE: a/c cool to hot
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Thanks to all of you for your comments and suggestions. I will probably get it checked by a mechanic who specializes in a/c. I'll let you know what I find out.
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FredDQC
Dodge Dakota
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8/02/2002
17:55:24
|  RE: a/c cool to hot
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I had the same problem and found out that the electric fan fuse was burned. So I would check that first. turn on the truck and a/c and check that the electric fan turns on.
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Bill Smith
Dodge Dakota
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8/02/2002
23:17:12
| RE: a/c cool to hot
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one more thing ya'll forgot to mention to Skywalker is that, R134a is slightly less eficiant at an ide in most vehicles ,BUT MORE eficiant at cruising speeds. I personally have a 96 Dak 4x4 with 134A and when i sit at lunch with the air on , it IS warmer than when i'm driving. I have no axilery cooling fan ,just the f16 clutch fan. Wouldn't be a bad idea to have the charge amount checked... being an EX-dealer tech, I've seen cars come through undercharged,but it's been in the90's here in Ohio and my a/c struggles at times. Hope this helps.... Bill
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Bruce P
Dodge Dakota
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8/03/2002
22:51:31
| RE: a/c cool to hot
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Have you applied the well-proven "AC mod" to your 2000 Dakota?
I am aware of many folks that have applied it and even one guy (an engineer) actually used thermocouples before/after the "AC mod". (You know how engineers want to 'measure' everything ;-)
Bottom line: 10 degrees colder air from the drivers-side center vent with the "AC mod" installed. (this was at approx 90 degrees outside temp)
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WallyR
Dodge Dakota
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8/03/2002
23:41:59
| RE: a/c cool to hot
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bruce,
what is this magical "a/c mod" that you are referring to?
bill,
you're halfway right. r-134a has fewer btu/lb than r-12 does-across the board (known as it's enthalpy). it's "efficiency" doesn't change just because your idling, it's the condenser's lack of airflow and the low compressor rpm's that increase the louver temps.
wally
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Bill Smith
Dodge Dakota
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8/03/2002
23:52:25
| RE: a/c cool to hot
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sorry was trying to keep things in "laymans" terms. point was, being an ex gm/Jeep teck, I've had numerouse complaints about lack of cooling at idle from all kinds of models. From riviera's to caddy's to trucks. your right,134a needs more air flow across the condenser tham MOST vehicles can provide ,without having adicuate cooling fan capacity...Thats why most big frt drive GM,at least, cars have 2 cooling fans . Sorry for the miss information. BILL
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bubba
Dodge Dakota
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8/04/2002
01:14:05
| RE: a/c cool to hot
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Insulate the low pressure lines and can!
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WallyR
Dodge Dakota
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8/04/2002
08:42:42
| RE: a/c cool to hot
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Good idea, bubba but it didn't have a measureable effect when we tried it. The refigerant on the "low side" of the system is travelling so fast that there is not much heat gain between the evaporator out and compressor in. You can lower the gas temperature entering the compressor but not by enough to gain any performance. Why Chevy does it we don't know-probably once again grasping for any little gain they can get, just like with their engines!
Bill,
Didn't mean to sound brash, just wanted to offer a little more info.
As for being a Jeep tech, You can blame only JTE for putting a nine cubic inch compressor on a system with a condenser the size of a tranny cooler. Those things were terrible!!
Wally
Wally
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Bruce P.
Dodge Dakota
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8/04/2002
21:12:40
| RE: a/c cool to hot
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All I can tell you that everyone else that has applied the "AC mod" has noted a difference.
In my case, after driving for about 30 minutes, the AC is now so cold that I have to turn up the heat a bit. in previous years, (before applying it) my AC could work all day long (16 hour trip) and never make it so cold that my passengers complained.
I do not know about the speed of the refrigerant but I look at it like this:
If the pipes under the hood are getting cold enough to sweat, then they are 'losing cold' (picking up heat) unnecessarrly. This is basic physics.
Perhaps it is the choice of materials or applicaiton of the insulation that is different in your case?
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Bruce P
Dodge Dakota
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8/04/2002
21:18:49
| RE: a/c cool to hot
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Here is my underhood pic. It shows the stick-on alumininum-faced insulation on the can. You can also see the insulation on all the pipes from the firewall all the way to the intake of the compressor. There is also a sectin of pipe that needs insulated that is BENEATH the AirFilter housing. This is where the hi-pressure ends and the low-pressure starts. (this section of pipe gets VERY cold)
http://members.aol.com/_ht_a/peebs4u2/dak1.jpg
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WallyR
Dodge Dakota
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8/04/2002
21:45:40
| RE: a/c cool to hot
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No, Bruce, that is basic thermodynamics. The surface of the tubing is below the wet bulb temperature (dew point) of the surrounding ambient air, hence condensation.
If this "engineer" that instrumented his vehicle to demonstrate the effectiveness of this modification has data I'd like to see it. I'm trying to be open minded about this but have a hard time believing that $2 worth of insulation made a system that did not perform at all for 16 continuous hours suddenly make someone turn on the heat after 30 minutes. That falls into the "supernatural" catagory to me.
Wally
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B
Dodge Dakota
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8/05/2002
00:11:29
| RE: a/c cool to hot
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B
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