AC help
 

1989 300e, need help finding source of problem, sometimes ac blows ice cold, sometimes blow warm, need a list of items that could be causing this. Anyone ever had this problem, how do you fix it. Help, help, help.

BAd fuse, only works sometimes (usually you get only defrost then, too.

Stuck monovalve, check for warm heater hoses, should be cool with AC on when it's hot.

Bad Klima relay, won't run AC compressor.

Bad serpentine belt, slips on AC compressor, Klima relay shuts off AC because the compressor is slow (this it to prevent the compressor siezing and stopping the engine).

Stuck expansion valve, or clogged orifice, so that no freon is moving (need gauges to verify).

Bad PBCU, won't run temp properly.

Bad hose to the interior temp sensor, so that the climate control is reading the temp under the dash next to the evaporator instead of the air temp - see if you have gentle suction at the little grille next to the dome light, if not , the hose is behind the glove box.

Peter

psfred

Maybe you can help me with my ford air wasn't working.
charged system with a 134A kit I got at autozone compressor started to cycle after a can and a half of freon was added but no cold air checked gauge that came with kit show that freon was in the blue zone of guage which should mean theres enough freon, yet the compressor cycles on and off every few seconds with no cold air coming out.
What could be wrong?

Ford uses CCOT systems, I think -- that is, cycling clutch orifice tube. You should have a large accumulator up by the firewall, with a large suction hose (the cold one) going to the compressor.

Did you evacuate the system and verify no leaks? If not, you probably have water frost forming around the outlet of the orifice tube, and no freon flow. When the pressure drops, the switch on the accumulator shuts the compressor off (this is the freeze protection system).

Does the engine really load down when you switch the AC on? This could mean the orifice tube is clogged (I can tell stories about a certain Volvo....).

Tell me more, I may be able to help, although I would never claim to be an AC expert!

Peter

Didn't evacuate system, engine does not load down compressor just cycles on and off and doesn't cool.

Probably lost most of the freon out the original leak.

Unfortunately, it is impossible to fix and AC system without a vac pump and some sort of leak detection.

Best thing to do, IMHO, is to replace ALL the o-rings, then take a good look at the orifice tube -- its in the small hose connection at the evaporator. If it is clogged with gray crap, you need to flush the system to get the crud out and replace the orifice tube -- when it is clogged, freon cannot get through, you get very low suction side pressure, and the compressor cycles a lot with no cooling. Also tends to blow the high pressure hose out (don't ask how I know!).

Unless you can evacuate the system, it won't work properly -- more than a very small amoutn of air prevents the freon working like it should. I'd also suggest a proper gauge set, not the little high side tester. You really need to know what's going on to get it working properly.

Peter

Or you overcharged the system with the Auto Zone kit. This is but one of many possibilities. Manifold gauges in the hands of a skilled individual would be a good starting point.

Not to be picky, but R134A is not Freon. Freon is R-12.

Freon is a registered trademark of DuPont, INC used to refer to a large number of halogenated hydrocarbons. Freon R12 is, I believe, trichorofluromethane, Freon R134a is tetrafluorethylene, there are many others. All are solvents, some are refridgerants (R34 is the one normally used in household and industrial units rather than R12).

Tetrachloroethane (I forget the number at the moment) is an industrial solvent often used to determine hydrocarbon contamination in soils and water, because it is fairly simple to evaporate and it has no carbon-hydrogen bonds. This means an infared spectorphotometer can easily be used to measure the presence of hydrocarbons, which do have carbon-hydrodgen bonds. Banned by the EPA since 1999 or so.

R12 was used in automobiles as being the cheapest and the lowest pressure cycle, not because it was the best.

Peter