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Armin
Dodge Dakota
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5/17/2006
12:25:06
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 Subject: A/C performance
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Now that summer is around the bend, I notice my '97 V6 Dakota struggles to produce enough cold air on those rather warm Texas days. It cools the intake air down about 25-30 degrees F on MAX A/C, but it only feels barely cool enough while driving around on a hot day.
I checked the refrigerant charge w/ one of those small guages that read the pressure from the low-side servicing port and it seems to be OK. My next idea was to check for a restriction or blockage in the evaporator/blower ducting, but before tearing the dashboard out, I want some easier things to check. Any ideas?
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Big Ed
GenIII
5/17/2006
21:14:38
| RE: A/C performance
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You said it "seems ok". What was the pressure??? It should be around 35 psi and a cold suction line back to the compressor when running.
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Armin
Dodge Dakota
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5/18/2006
12:02:56
| RE: A/C performance
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The low side reads about 47 psi, which I know is too high according to a manifold guage, but I used a charging kit from a parts store which has a single guage that reads the charge from the low side servicing port. According to this guage, 47 psi is in the "normal" range for a fully charged system based on the temperature for that day (85 F).
The suction line to the compressor IS cold. My Haynes manual says that the the line going TO the evaporator should feel cold and the line coming FROM the evaporator to the compressor should be slightly colder, which sounds strange to me because it seems that the line coming out of the evaporator should be warmer since it absorbs the heat from the air drawn through the evaporator by the blower fan.
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daddio
Dodge Dakota
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5/18/2006
12:39:30
| RE: A/C performance
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you really need to put gages on both sides to see exactly whats happening in there. it could be a restriction or it could be worn valves in the compressor. it's hard to tell with just one gage.
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Big Ed
GenIII
5/18/2006
15:45:35
| RE: A/C performance
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It does sound strange but thats the way it is. If you have a Central System in you home, feel the insulated line at the condenser, its cold and sweaty too. (thats the low side) I doubt a restriction or your suction pressure would normally drop. If your suction line is cold its probably ok. 47 psig sounds high regardless of the haynes manual. 35 back pressure gives you a 38 degress evap coil temp. The higher the pressure the higher the temperature. If its really hot inside your truck, it'll take a few mins to cool it down, when its really hot in there, the low side could be up there, but normal operating would be 35 or so.
Did you run up the rpm's to about 2k with the gauge on?? It should drop to around 35 when the rpms are up.
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Tfw
Dodge Dakota
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5/18/2006
16:50:26
| RE: A/C performance
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Bet it's overcharged.
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Big Ed
GenIII
5/18/2006
16:58:18
| RE: A/C performance
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I agree with you Tfw, or bad valves.
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Obio3
Dodge Dakota
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5/18/2006
20:18:03
| RE: A/C performance
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Posibility the heat/ac valving isn't turning the heat all the way off. maybe vacumn leak or a vent door stuck or malfunctioning partially.
> just a thought
So many problems ... So little time
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Armin
Dodge Dakota
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5/20/2006
11:39:17
| RE: A/C performance
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What should the high side pressure read for normal operation?
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shatto
Dodge Dakota
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5/20/2006
18:33:14
| RE: A/C performance
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Cools to 25-30 degrees?
That is 5 to 10 degrees colder than it should be. It's freezing up.
Your A/C, on a long run can keep you about 15 to 20 degrees cooler than outside. If you have the newer body style. That's what my 98 regular cab does.
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Big Ed
GenIII
5/20/2006
20:31:10
| RE: A/C performance
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No way will it freeze up with at 45 psig pressure.
High side pressure will vary with temperature and engine rpm. it'll be in the 200's somewhere.
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Tfw
Dodge Dakota
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5/21/2006
13:06:10
| RE: A/C performance
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I could be wrong here, but I assumed Armin was talking about 25-30 degrees cooler than outside air temperature. If that's the case, it should do alot better than that. Big Ed's right.
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shatto
Dodge Dakota
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5/21/2006
14:18:47
| RE: A/C performance
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So we are clear, because some are talking air temperature and some Freon pressure;
The temperature of the air coming out of the vent should be around 35F.
Much colder and the system will likely freeze.
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Obio3
Dodge Dakota
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5/21/2006
15:35:36
| RE: A/C performance
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Get a fruit thermomater. It has a stem on it. Stick it in the vent and see what the temp really is. It will tell you if you truely do have a problem.
So many problems .... So little time
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Armin
Dodge Dakota
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5/23/2006
11:12:26
| RE: A/C performance
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No way does it cool to 25-30 degrees as Shatto assumed. The coldest the duct temp. reached on an 85 degree day was in the high 50's. I used a temp. probe from a digital multimeter placed well inside the center vent duct, so this reading is pretty accurate.
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Lurkin
Dodge Dakota
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5/23/2006
15:02:44
| RE: A/C performance
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The health of the AC system is not measured by a set tempurature of the air coming out of the AC vents, but rather the difference in the outside air temp and the air coming from the vents.
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Big Ed
GenIII
5/23/2006
15:42:06
| RE: A/C performance
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Actually, the health of an A/C system would be by measureing the refrigerant pressures and them being at the proper readings, airflow from the evap fan and vents, ect. return temperature vs. discharge temp at the vents. A 20 deg split between return and discharge air would be excellent.
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shatto
Dodge Dakota
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5/24/2006
01:29:46
| RE: A/C performance
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Armin,
Sorry for not being clear.
My 98 standard cab can get down to 35 degrees, on the probe thermometer, at the center vent. When the outside temperature is 100+ outside, the cab will be around 80 inside. Maybe it could cool more but I'm not smart enough to remember to use the recirculate setting.
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Armin
Dodge Dakota
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5/25/2006
11:04:43
| RE: A/C performance
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So without breaking down to get a damned manifold guage, can I assume if my A/C is dropping the outside air temp by about 20 degrees that it's doing its job (given the age of the system--9 years)?
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Tfw
Dodge Dakota
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5/25/2006
14:04:36
| RE: A/C performance
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As I stated earlier it should do a hell of alot better than that. My 98's a/c has never been touched and will still produce at least a 50 degree split here in Phoenix area. Naturally it takes quite awhile if it's been sitting in the sun all day. Could be alot of things. Charge, compressor, mode door, condensor flow, expansion valve.
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Bump
Dodge Dakota
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6/01/2006
02:26:42
| RE: A/C performance
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Bump
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