AC issues...again!!!

559 Views 1 Reply 2 Participants Last post by wmburns, Jul 13, 2011

littlejessie

Discussion Starter · Jul 13, 2011

Well I'm back again scratching my head. In the last two years I've replaced my ac compressor three times, this last time I replaced the compressor, flushed all the lines, replaced the orfice tube, condensor, and accumulator. Installed 2lbs, 2oz of freon with an ACR2000, installed the correct amounts of oil into the system, pressures have been at factory specs, ac has been working great.....up until yesterday!!!! Last year I had to replace a leaking suction side shreder valve cause my ac was cycling off and on too much and wasn't cooling efficiently. I pulled a 45 minute vacuum @ 28in of vac. recharged the ac last summer and haven't had a problem till this week. Yesterday I pulled into a steak house after work to have dinner with co-workers. We were there for about an hour, the temp outside (Round Rock, Texas btw) was around 99-100 degrees. Car was alread @ operating temperature when we got back in to head home. Temp inside car said 141 on the thermometer in the ac vent, turned ac on high it dropped down to about 58 degrees, pulled out of the parking lot up to the stop sign to get on the freeway, ac compressor turned off for about 10 seconds, then turned back on, I took my foot off of the brake pedal and began to accelerate, ac compressor turned off for 10 seconds again, then back on, as I got onto the freeway it got cooler, droping down to about 42, then 38 degrees. Didn't do it again so far, haven't found any leaks yet. What could be the problem???? Also my compressor ONLY cylces if its on defrost, low, or medium-low. If I have it on medium-high, or high in never cylces, and the compressor doesn't turn off if I put my foot into the accelerator. If I want to pass someone I have to turn the compressor off. I've replaced the low-side pressure switch once, is there a high-side switch or are they the same switch?

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wmburns

· #2 · Jul 13, 2011

Post is a little hard for me to understand.

However, I can help with some information. First are you aware that the PCM is in full control of the AC compressor? As such, there are conditions where the PCM will shut off the compressor by design. For example at WOT, when the motor is overheating, or when the head pressure is too high.

There is a separate switch for high head pressure.

Start 1st by looking at the fans. Are the fans working on? Is the radiator clean? Are all of the shrouds and air dams in place?

At the end of the day, this simply could be it very hot outside.

As for why compressor cycling doesn't occur at higher fan settings, it's because at higher fan settings, more heat is rejected. Slower fan settings reject less heat and therefore allow the pressure to drop lower.

Just wondering how you are monitoring the AC. If with a temperature gauge in the registers, 38 degrees is a tad low. I would expect the AC to cycle at that low of a temperature. Remember what happens if the temperature gets to 32 degrees? Water will freeze on the coil.

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