MECS pump was replaced before I purchased the car. About 10k miles ago.

And the contaminants may be a possibility, but it seems that the rear AC is working only some of the time, even though the temperature is very high. When it works it gets cold pretty significantly, and when it doesn't it's just as warm as the ambient temp. It's not just kind working halfway, it appears to be either on or off.

 

Update!

I did get it working this morning on my way to work... kind of.

So it has been hot here in Texas the past week (highs from 95-100) and I have been using the cabin AC on it's highest setting (4) or second highest setting (3) and I haven't turned it down past 3 I believe since this problem has started happening.

This morning it was slightly cooler so I turned my AC down to 2 and I noticed the battery (which was not cooling at all yesterday and was at 102* when I got home late last night after leaving the car in MAX AC setting all day) temp start dropping. I was on the highway in moderate traffic going about 50 so I went ahead and rolled the windows down and turned the cabin AC completely off thinking the compressor could dedicate itself to the battery cooling completely.

Once I did that I was able to get the battery temp into the low 80's fairly easily and by the time I got to work it was at 80.6*.

Now this is good news and bad at the same time. It's good because I know there's no major mechanical failure to worry about, but it's bad because it seems as though something is wrong enough with the AC to not be able to handle both front and rear systems simultaneously when it's hot out. I have had days where it was very hot and I used the AC in the cabin on 4 and still had the battery cool off several weeks ago, though.

Now the only thing I can think of is that it barely needs a freon charge to support both AC systems, but I checked the charge yesterday and it was in the middle of the "charged" range on the gauge. Do the FEH's require a slightly higher charge? Does anyone know what the best pressure to have in the system specifically?

Thanks again for the help.

 

I happen to be working on two different car's AC system although these are the older R12 systems, I've been reading plenty.

Some if not all R134A systems are touchy on the amount of freon but the only way to have the correct amount is to evacuate and charge by the weight shown on the tag on your system. Pressures are just used for trouble shooting so there is no best pressure.

 

These days a DIY 'charge' is a pretty good way to mess up a sealed system, and is probably what the OP's car has had in the past. Condensation or just outside air in the lines would explain the lack of/inconsistent performance in hotter conditions. Colder air is denser and probably insulates better.

 

Ahh I understand.. Man.. I can work my way around an engine all day, but I just don't understand A/C systems.


Interesting. So is the best thing to do is to take it somewhere and have it emptied and then replaced with the proper amount (not pressure) of freon?

 

I have a vacuum pump, gauges, etc. purchased probably in the early eighties which was the last time I touched an AC system. I was thinking about converting to R134A. They make it sound so easy with these kits. In the AC forums they call them Black Death Kits. Black Death is what a burnt up compressor is called.

There is the cheapest conversion where you change nothing but it may not work at all or perform poorly. Then you get into replacing a part or two. The best is a full system gutting.

I had five cans of R12 for one vehicle but bought four cans off Craig's List for $25 a pop for the other vehicle. The guy said that he bought some at K-Mart for a dollar.

 

It's the safest but some have it removed and refill themselves. I'm wondering myself when this is done, in what state is the system? Normally, it's evacuated using a vacuum pump and charged while still under a vacuum. A AC Tech use a recovery system so I don't know what a DIY'r would do after that. If you connect to a port it'll suck in ambient air which one doesn't want. Seems like one would need a vacuum pump and gauges at least.

 

I'm in Texas. To be honest, I don't even want to deal with it. I feel like this is too complicated of an A/C system for me to try and figure out how to mess with it. This is the only time where I'd feel comfortable paying someone to fix it.

But I really appreciate all of the info, guys. Truly.

 

In Texas, you need AC! Hope you don't need K-Y Jelly to go shopping for a AC Tech?

 

Truth! Haha!!