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Old 06-09-2008, 02:20 PM   #1
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A/C Question

I am trying to find out for my dad what is wrong with his A/C on a 1994 Ford Escort. He and my mom are both in their upper 70's so they need the A/C on these hot summer days. I haven't looked at it, but he said the compressor would run with the fan on the lowest speed and stop running when he turns the fan to a higher setting. I was wondering if switching the fan to a higher setting affected pressure on the A/C compressor. I know it has a low pressure switch and a high pressure switch, but I don't know what their function is. Anyone know or have any ideas?
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Old 06-09-2008, 02:48 PM   #2
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I don't know about the electronics of switching fan speeds, but I have seen some systems act that way that are overfilled with freon. Has it been converted to R134? Or is it the original R12?

If its been converted to R134, you can get a gauge/fill hose pretty cheaply at Wall mart to check and see it its over or undercharged. The high pressure switch will shut off the compressor if is overcharged and the low pressure switch will do the same if its undercharged.
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Old 06-09-2008, 02:59 PM   #3
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I don't know about the electronics of switching fan speeds, but I have seen some systems act that way that are overfilled with freon. Has it been converted to R134? Or is it the original R12?

If its been converted to R134, you can get a gauge/fill hose pretty cheaply at Wall mart to check and see it its over or undercharged. The high pressure switch will shut off the compressor if is overcharged and the low pressure switch will do the same if its undercharged.
I am not sure about whether it has been changed over or not. I know it is not because of being overcharged because it was working last summer and hasn't been serviced since then. I have been told you can add R134 to systems with R-12 in them without removing the R-12 do you know whether this will work or not? I know the fittings would have to be changed in order to put in the R134, but you can buy the conversion kits at Wally World for a few dollars. Erik where do you live in western KY? I am originally from Elkton, KY, Todd County that is where my parents live and I am planning to be there later this week and wanted to check it out for them while I was there.
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Old 06-09-2008, 03:10 PM   #4
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I haven't heard of anyone adding R134 "on top of" R12. Since there is likely a little R12 left when people convert over to 134, I kind of doubt that it would hurt anything.

Hopefully someone more knowledgeable will reply.
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Old 06-09-2008, 04:40 PM   #5
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Not sure how a Ford wires the AC, but a Honda grounds one of the signals that allows the compressor to turn on through the fan switch. This is why the AC won't turn on unless the fan is running. Maybe your fan switch is broken? Otherwise, I don't see why an AC would care about the fan speed.
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Old 06-09-2008, 04:45 PM   #6
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R12 and R134A not compatible

I'm not expert, but my research last year showed simply adding R134A to R12 will cause a corrosive result in not too much time, ruining your system.

You can flush the lines, compressor and accumulator/dryer with a special flush available at auto stores, vacuum the whole thing down to cause all moisture to boil away and recharge with R134A and compressor oil.

Auto Zone will loan you a vacuum pump to evacuate the system through their tool loan program.

I'd also been told that flushing doesn't really get the old junk out of the accumulator/dryer, so I replaced mine to be safe while flushing the lines. (I was putting in a new compressor anyway.)

Flushing is kind of a messy, crummy job (wear goggles!) and replacing the hardware is not something you'll do real quickly if you're just in town for a quick visit.

Sorry it's not a simply recharge if your parents have an R12 system. Not sure how long R134A has been the standard since my "D" is a 1982, but I'm guessing since the late 1990's.

If they already have R134A, it's pretty easy to get a can of R134A and oil with the hose already attached for perhaps $15. You'll be recharged in a few minutes. A slightly more expensive can ($30?) has a gauge to prevent overcharging.

Hope this helps and I haven't misinformed. FWIW, I haven't had any problems in a year. Keeping my fingers crossed.
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Old 06-09-2008, 05:10 PM   #7
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I've seen the blower resistors heat/burn up on escorts/contours and melt the fan control switch on the connector side. the fan switch controls the blower speed, not the ac compressor. so it doesn't matter what speed of the inside fan is ,the ac should be coming out of some vents unless the fan is off then no ac. Also a note , i think the escort has the ac on/off button right in the middle of the fan knob, it should be lit up blue color when on.
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Old 06-16-2008, 03:07 PM   #8
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Thanks everyone for the suggestions. It was really crazy the compressor would run on #1 fan speed only, but the fan was not working on that speed the fan would work on #2 fan speed, but the compressor would not run. Neither the fan or the compressor would run on fan speed #3 or #4. If anyone runs into a problem like this check the connector where the fan switch wiring is connected to the blower motor. The plug had overheated and burned one of the wires in two and a couple of the other wires were burnt on the outside, but I don't know what kind of shape they were in under the plastic insulation. I went to the junk yard cut a plug off of another Escort spliced it into the original wiring and everything worked perfectly.
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Old 06-16-2008, 03:34 PM   #9
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Thanks everyone for the suggestions. It was really crazy the compressor would run on #1 fan speed only, but the fan was not working on that speed the fan would work on #2 fan speed, but the compressor would not run. Neither the fan or the compressor would run on fan speen #3 or #4. If anyone runs into a problem like this check the connector where the fan switch wiring is connected to the blower motor. The plug had overheated and burned one of the wires in two and a couple of the other wires were burnt on the outside, but I don't know what kind of shape they were in under the plastic insulation. I went to the junk yard cut a plug off of another Escort spliced it into the original wiring and everything worked perfectly.
Sounds like you have a problem with the blower motor circuit. The motor is not moving air over the evaporator coils so eventually the system is overpressurizing and shutting down the compressor. You may still be low on Freon, but that can't be properly assessed until the blower motor is fixed. Its common for either the resistors or the actual fan speed switch on the dash to go bad. Usually when either of these 2 goes bad it is obvious when you look at it. They will usually look burnt & melted.
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Old 06-16-2008, 04:54 PM   #10
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Sounds like you have a problem with the blower motor circuit. The motor is not moving air over the evaporator coils so eventually the system is overpressurizing and shutting down the compressor. You may still be low on Freon, but that can't be properly assessed until the blower motor is fixed. Its common for either the resistors or the actual fan speed switch on the dash to go bad. Usually when either of these 2 goes bad it is obvious when you look at it. They will usually look burnt & melted.
After replacing the faulty plug both the fan and compressor worked perfectly. There is no problem with the freon level. After driving approximately 15 minutes in 90 degree temperatures the fan could be turned down to the #1 position and maintain a comfortable temperature. We drove the car several times over a 5 day period and there was no failure of the compressor or fan.
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