2005 Freestar air conditioner, get in and it wont engage clutch, next time it will, sometimes it wont. Tonight it would not work on way to eat, got back in cranked it up, it cooled fine going home. Two ac shops (one was Ford Dealer) cant figure out why, although got charged the diagnostic at Ford anyway, local ac shop said we cant fix it so no charge.. anyway this is real bothersome, its geeting summertime. Has full charge of freon, and when it does not work if you jump compressor from battery, it will run fine.Any ideas or sugeestions??? Thanks

 

Sounds like an electrical issue with a HIGH/LOW pressure sensor or temperature control switch. Do you have the Manual or electronic temperature control?

 

It is not automatic, you have to turn it on ac or heat, you cant set a temp and it maintain that temp by cooling or heating, this one has a **** to choose heat, vent, ac, max ac, etc. It also has rear air. I would assume it is a manual temp control by the switches and controls. Took it to yet another shop. They suppossidly " cleaned out the system by flushing and putting new freon to the OEM specs" as they put it, removed and checked, then reinstaaled the cycling switch and replaced the ac control head(control panel inside cabin with all the controls on it to turn it on etc..) and presto,, it quit again on my wife on the way to a meeting later in the day, then worked again about 2 starts of the engine later, and worked till she got home so more $$ gone and still like it was. I switched a couple of fuses and relays with like ones, switched them around to see if those were bad, in the power box under hood and the one under dash by looking at diagram in manual. Made no difference. Hope this helps in a deduction of what to try, and thanking in advance for any info on what to do next. My wife is really getting frustrated.

 

A/C systems normally don't get "FLUSHED" unless you have a compressor failure. I have to assume that since the shop "FLUSHED" the system, they replaced the front orifice, the rear expansion valve and the dryer/accumulator with new ones as this would be the proper procedure for flushing the system. NEVER flush through a compressor, drier or expansion valve. You will ruin them. The system gets flushed in sections when flushing. ALWAYS try to flush opposite the direction of flow whenever possible. You do not want to flush the contaminants deeper into the component you are attempting to clean. Technically the new multi-pass, 6mm tube condensers are nearly impossible to properly flush and is normally replaced if debris is found on the front orifice. They then should have added 12 oz. of PAG oil (I prefer using Polymax2 as it's a Non-Hygroscopic oil and works in R-12 and R-134a systems) and 53 oz. of R-134a. I can go on and on with the system flushing do's and don'ts and such but, I probably go overboard when I do stuff.

Anyways, Does the A/C put out cold air in the rear when it's not putting out cold air to the front? Since technically the front and rear A/C are two seperate systems with a common compressor and condensor. If this is the case I would check for vaccum leaks (poor fitting connectors and loose/cracked lines under the dash and and at the control head (temperature control switch). You may have a problem with the vacuum operated temperature "BLEND" door in the dash.

 

The rear air works fine when the front air works, no problems there. When the ac doesnt work, the compressor will not engage at all...My wife has turned the ac on with me watching the clutch to see if it engages and when the problem pops up, it will not. However if you disconnect harness at compressor, and jump from battery, it will work. The first ac shop did this and showed me it engages then, said it was a bad PCM..needed replaced???but they didnt do that type repair. Dont think they really knew. The last guy did all that flushing for 65.00 dollars...so I dont think he did all that you said, I really question his flushing at all, but all that said, Last time I talked to tech at local Ford, they want to simply but all new system in for $1700.00 to $2000.00. When working, it can be 85F outside and 38F to 48F at vent. Clutch does cycle when it works, I have watched for this. This van has 78000miles and this is first problem. Mechanic told me to look at PCM and check wiring connectorfor moisture. He said it was common problem. I did this and saw none. Bolts on PCM were still steel colored, not rusty so I dont think it is geeting wet. Thanks for your input in our situation. Got any 1964-66 Mustang body questions? I have done several of these in my years,know those body lines in my sleep.Thanks

 

SAMF - there is a water intrustion TSB for the Freestar. Water / moisture penitrates the seal in the firewall and causes intermittant issues with in the PCM (moisture cools & condinstates). You most likely will never see "rust" on the hardware as it is a small amount of moisture.

 

Remember, we're just hunting and pecking at possibilities. With this said...here's a couple of other things to check.

I would also check all of the ground connections. A flakey ground can cause the Freestar electronics to do weird things since Ford uses the ground system to transmit PCM information to the different modules and ECUs. Check/clean the multi-ground connections on both sides of the radiator support under the black cover, and the ground lead connected at the dryer/accumulator. You might also just have a flakey LOW pressure or HIGH pressure switch for you A/C. The LOW pressure switch is located on the bottom edge of the dryer/accumulator and the HIGH pressure switch in located on the HIGH pressure line muffler directly below and in between the radiator fans.

 

Possibly a bad a/c relay.