2003, 4.7, rear a/c. Here is the deal. Been to 4 mechanics, read as much as I can on here, may have over looked this topic, but can't find it.
When the durango is idling or running down the road, the air is cool. Not cold, just cool. It has a new e-fan, has been charged 3 different times. The freon lines are cold. Compressor works. BUT, when you turn on the rear a/c the compressor starts working for 3 to 4 seconds and then off for 3 to 4 seconds. The air turns warm. Turn rear a/c off and the compressor starts working normally and cools down the front again, NOT COLD just cool. I also noticed recently that it does not leave a puddle of water anymore. HELP PLEASE

 

I'm not familiar with the rear A/c systems, but a quick thought is if there is a seperate coil for the rear? Sounds like there is a clog in a line, but that only makes sense to me if there are 2 coils (the coil for the front works fine, but the rear is clogged)

I would also check the filter and see how it looks.

Just my $.02 worth....

 

Also, side thought are expansion valves. Thinking you might have 2 of them...

 

Sounds like the low side switch is bad. Or it could be the high side not letting it get high enough pressure.

Basically the compressor is turned on when the low side switch reaches the low psi setting, then as the pressure builds there is a high side switch and when the pressure gets to it's set point the high side switch turns off the compressor. Then the pressure slowly falls until it reaches the low set point and the compressor cycles again on and off keeping the PSI in the range needed.

So to me I see a few issues it could be.

1. The high side switch isn't functioning right and not letting enough pressure to build before turning off the compressor.

2. The low side switch isn't functioning right and not letting the pressure fall enough before turning on.

3. The expansion valve is letting too much fluid through and dropping the psi to fast so the compressor is turning on and off fast.

4. They just don't have enough freon in the system. On the charge sticker there are 2 different load levels, one with rear A/C and one without rear A/C. If they are only filling enough freon to the just front level then there isn't enough freon in the system and that could cause the issue.

I would hook up to the high side and low side and watch what is going on with the correct set of gauges. Either the pressure isn't building correctly, isn't falling correctly, or is falling too fast. Also you could have them e-vac it and see if they have the right charge in for the dual system.

Could also be a bad filter.

 

Thanks guys for the response, I have no idea about this filter yall are talking about. Oh yea, I placed a thermometer in my vent, it was reading 80 degrees while driving and around 68 idling. So I guess it wasn't as cool as I thought.

 

OK, here we are: Another mechanic told us today that the radiator fan clutch needed replacing, because that fan wasn't pulling enough air. I did not think this would work or made any sense at all, yet 50 bucks and 2 hours later, I was proven right. I mean isn't that why we have an e-fan??? Ok, pressures checked again and again they are correct, but for some reason , at idle the temp is around 65. Driving down the road the temp now reads 80. I have discovered one other thing, the compressor turning on and off every 3 to 4 seconds, was because the rear unit was on. We turned it off and the compressor started working normally. However the rear unit does not work at all, but hey, I would just settle for comfortable right now. It is suppose to hit 97 this weekend. Starting to think the answer might be driving nude with the windows down... anyone have a better idea???????????

 

One other thing, just noticed, at 1500 rpms the compressor turns on and off every 4 second with just the front unit on. At 750 rpms the compressor runs continuously.

 

Problem solved... to much freon !!! Finally found a mechanic that knew how to check the freon.

 

thanks for letting us know what the solution finally ended up being