2nd Gen Non-Engine/Transmission Poor AC performance

[MAllen]

My 98 dodge has started not working as well. Everytime on a hot day when I stop or slow down, the ac compressor will kick off and the ac will not be cold. Does anyone know what can fix this. The compressor was new as of last fall, and I had it vacuumed and recharged. I did change the drier when I installed the compressor. Any thoughts? THanks

 

[Matt42]

Some things I can figure out. This isn't one of them. The people at Arizona Mobile Air have a forum at their website, here: Automotive Air Conditioning Parts & Equipment - ACKITS. COM The forum link is in the text of the home page. I have dealt with them before, on the forum, by mail and over-the-counter.

 

[monkeyman]

That year had evaporator problems
Rick

 

[drag racer]

My 1999 has never worked what I would call great since the day it was new. Considering the relatively small cab volume compared to a large car or like a Suburban, the A/C should freeze you out pretty easily in these trucks. I agree, they missed something in the system design somewhere, but I don't know exactly what it is. The only good thing is mine has not gotten any worse after 9 years with zero maintenance.

 

[BDaugherty]

The situation that you described makes it sound like your system could be overcharged. When you stop, you loose airflow and your high side could spike high enough to kick out the high pressure switch. That could cause the compressor to disengage only when you stop. Further diagnosis may be necessary. Does it cool well when driving? How is the aiflow? Have you removed the blower motor and checked the evaporator coil for restriction?

 

[Matt42]

The situation that you described makes it sound like your system could be overcharged. When you stop, you loose airflow and your high side could spike high enough to kick out the high pressure switch. That could cause the compressor to disengage only when you stop. Further diagnosis may be necessary. Does it cool well when driving? How is the aiflow? Have you removed the blower motor and checked the evaporator coil for restriction?

A good observation. An R-134 overcharge will produce those exact symptoms. Back in the old days, R-12 was more forgiving to a slight overcharge or undercharge. I've found that a slight R-134 undercharge works better than an exact charge. When I last evacuated and charged, I watched the center register temperature. It bottomed at 20 ounces, then started to rise. (The factory service sticker says 22 or 24 ounces, I think. ) On a previous occasion, I had overcharged it to about 28 ounces using my R-12 experience. That caused the pressure switch to cycle on and off, and give very bad performance.

It's hard to get the correct charge on an R-134 system (in my limited experience) if the only tool you have is one of those can tap with a hose devices. It's very easy to overcharge. It also seems to be necessary to vacuum the system every now and then, and hold the vacuum for at least 30 minutes to boil out any moisture. Moisture in the system will produce suboptimal cooling. Some years ago, I bought the gauges and a vacuum pump, and they have paid for themselves many times.

The evaporators in the rough 1994 - 1999 years do have problems. Leaves and "humus" accumulate in the evaporator area and eventually cause a pinhole leak. It may take several months for the leak to degrade performance. Replacing the evaporator is not a job for the impatient or fumble-fingered, but it is doable. Since the heater core in that series also has issues, both should be replaced at the same time. Many people have observed that you need to use a MoPar evaporator. Trying to save $20, I tried to use an aftermarket unit. I ended ripping the job out again and installing a MoPar. Be warned. The MoPar unit has brazed-on tubes that are just enough more flexible and better fitting to permit you to snap together the connection to the receiver-dryer in a leakproof manner. the aftermarket evaporators look connected, but they will suck in just enough air or leak or both over time to cause trouble.

Another thing to consider replacing is the valve at the top of the condenser in front of the radiator. The valve has a name that completely escapes me right now. Many good condensors have been replaced when all they needed was a new valve or a valve cleaning. The valve is a plastic venturi-looking thingy that snaps into the low pressure outlet. You can remove it, carefully, with long needle nose pliers. The valve has a filter screen. After eight years of very heavy Arizona use, the valve on mine had clogged up with a black, gooey substance. I was able to clean it with lacquer thinner (first) and then denatured alcohol (second). Don't use isopropyl (rubbing) alcohol because it contains water. It is also possible to buy a new valve from ackits.com or locally.

The other issues of blocked evaporator, radiator and intercooler must also be checked. The fan clutch may also be bad. Because I drive in city traffic here, I added a 12 inch pusher fan to the front, which improves the AC in stop and go driving.

Disclaimer: I am not an AC tech, just a cheapskate.

 

[BDaugherty]

The "valve" that you speak of is actually an orifice. Some A/C systems use and expansion valve. Our Dodges use an orifice tube. Even for a cheapskate, I would replace the orifice rather than try to clean it... They're that cheap. Also, the black sludge that you found was a classic symptom of moisture contamination in a R134a system. If you're gonna have they system open, you should replace the accumulator/dryer. The dryer contains dessicant that will absorb moisture out of the refrigerant charge. If your dryer hasn't been replaced in a long time (or ever), the dessicant will have absorbed its limit and that would be the reason that you have to vacuum and recharge periodically as well as the reason for the black sludge. With A/C, the most cost effective thing to do is to do it right the first time and not have to touch it again... especially if you don't have recovery equipment and you're having to charge virgin freon each time.

 

[DonTX]

I don't feel the design was bad, my ol 97 club cab AC will run you out of there quickly, and I drive where it is VERY hot outside.

My 1999 has never worked what I would call great since the day it was new. Considering the relatively small cab volume compared to a large car or like a Suburban, the A/C should freeze you out pretty easily in these trucks. I agree, they missed something in the system design somewhere, but I don't know exactly what it is. The only good thing is mine has not gotten any worse after 9 years with zero maintenance.

 

[Matt42]

The "valve" that you speak of is actually an orifice. Some A/C systems use and expansion valve. Our Dodges use an orifice tube. Even for a cheapskate, I would replace the orifice rather than try to clean it... They're that cheap. Also, the black sludge that you found was a classic symptom of moisture contamination in a R134a system. If you're gonna have they system open, you should replace the accumulator/dryer. The dryer contains dessicant that will absorb moisture out of the refrigerant charge. If your dryer hasn't been replaced in a long time (or ever), the dessicant will have absorbed its limit and that would be the reason that you have to vacuum and recharge periodically as well as the reason for the black sludge. With A/C, the most cost effective thing to do is to do it right the first time and not have to touch it again... especially if you don't have recovery equipment and you're having to charge virgin freon each time.

Orifice. That's the word I was looking for. I replaced the accumulator when I rebuilt the system, but that's been about four years. They're not expensive. Probably ought to do it again.

 

[MAllen]

Where is that orifice tube located. I bought a new one when I replaced the accumulator/drier and could never find where it went at that time. I went out this evening and took the dodge for a spin and when I returned home just let my truck idle for a while with full ac on. After about 1 minute the compressor disengaged for about 10 seconds and then reengaged for about 1 minute and then did the same again. When I drive down the road with some rpm's, no problem at all other than the low airflow through the ductwork. I really want to get this thing back to the way it should be.

 

[MAllen]

Heres something I found that looks promising to cleaning the evaporator core, has anyone tried this before.

DWD2 - Products

 

[Matt42]

Where is that orifice tube located. I bought a new one when I replaced the accumulator/drier and could never find where it went at that time. I went out this evening and took the dodge for a spin and when I returned home just let my truck idle for a while with full ac on. After about 1 minute the compressor disengaged for about 10 seconds and then reengaged for about 1 minute and then did the same again. When I drive down the road with some rpm's, no problem at all other than the low airflow through the ductwork. I really want to get this thing back to the way it should be.

If your truck is set up the same as mine, it is in the low side connector tube coming up out of the condensor. You'll need a "Ford" type disconnecting tool to get it apart, and may need a new O-ring pair or triplet to put it back together. Follow the larger diameter hose and tube to the condensor, in front of the radiator. I really oughta replace mine again.