Jumped A/C cycling switch... Compressor kicked on. Now what?

94GTPilot · Oct 31, 2010

Just as the title says, I wasn't having any luck with the system kicking on when I turned the dial inside the car. I unplugged the switch on top of the accumulator, and with the dial set at Max A/C, the clutch engaged. I unplugged the paperclip, but now I'm not sure what I need to replace. If it's the actual cycling switch, do I need to take the car and have the system drained before replacement??

Thanks.

toyman · Oct 31, 2010

94GTPilot said:
Just as the title says, I wasn't having any luck with the system kicking on when I turned the dial inside the car. I unplugged the switch on top of the accumulator, and with the dial set at Max A/C, the clutch engaged. I unplugged the paperclip, but now I'm not sure what I need to replace. If it's the actual cycling switch, do I need to take the car and have the system drained before replacement??

Thanks.

The cycling switch just threads out. There is a Schrader valve that prevents the refrigerant from coming out when the switch is removed.

blksn955.o · Oct 31, 2010

Most times it is due to low press in the sytem...IE needing a recharge. IIRC what your actually jumping is the low pressure switch to force the system to cycle.

Have your pressures checked. You may need to have it filled and then have it tested to see if the system is holding pressure. Often with age things start to leak and they will put a die in to detect a leak.

94GTPilot · Oct 31, 2010

Ahh, so what I unplugged from the condensor and jumped was the low pressure switch? I was under the impression that if I jumped it, and the compressor kicked on, that it was a bad switch...?

I'll have to take it in and test the pressure. Or is there a gauge I can buy and test it myself??

HISSIN50 · Oct 31, 2010

You can check pressure yourself if you have a set of manifold gauges. Don't run it jumped for any longer than possible (i.e., no longer than 15 - 30 seconds).

If your pressures are good and there's power into the LPCS but not out, that suggests a bad switch.

As noted in your case, the issue probably lies elsewhere.

Good luck.

94GTPilot · Oct 31, 2010

HISSIN50 said:
As noted in your case, the issue probably lies elsewhere.

Good luck.

So you think it might be something other than the switch? I'm going to run to the parts store and pick up a gauge...

HISSIN50 · Oct 31, 2010

You're more likely to be low on charge than to have a bad switch. Manifold gauges are not super cheap but some parts stores might loan them out.

94GTPilot · Oct 31, 2010

Makes sense. I can get the system recharged for $30 here on base, am I better off doing that, and they can tell me if I'm low or not? Instead of forking up the dough for manifold gauges...

HISSIN50 · Oct 31, 2010

It takes all of about 30-120 seconds to check the pressures, so maybe the place on base can do it for cheap (or free).

blksn955.o · Oct 31, 2010

Hit up the place on base and then ask if you can come back in a week or two just to make sure there is no leak. They should have the die available but ask prior if they do so they will half arse be expecting you to show up. They will use a black light deal to find any leaks.

94GTPilot · Nov 2, 2010

Good deal. Thanks for the heads up. I will report back.

stangbangerrick · Nov 3, 2010

This is what they usually do when adding or charging the A/C on a car. 1. They draw out all the freon using a machine with vacuum, after the freon is out the machine is still connected and the vacuum reading is monitored over a period of time to see if the vacuum holds. 2. If the vacuum reading holds you dont have a leak in the system, then the system is recharged to spec. If the vacuum reading drops there is a leak and a dye is add through the valve and all connections and line in the system are checked for signs of the dye were they find the dye theirs your leak.

94GTPilot · Aug 29, 2011

Update... I know it's been a while, but flying has been pretty busy. I went and got the system checked out, turns out it was just very low on freon. Charged it up with 2 small bottles, and it blows cold air. The switch that I jumped turned out to be working just fine.

Thanks for all the help!

94GTPilot · Oct 11, 2011

Hmmm... update:

System worked great for about 2 weeks, then hopped in the car the other day and the compressor isn't kicking on. Took it back to the shop, we hooked up the gauges to the high and low side and confirmed there's plenty of R134 in the system. Could it be the compressor seized up? Anything else I should be checking?

I have been a bit too busy to fiddle with it, but I'll give it a good peek tomorrow. Maybe try jumping with a paperclip again?

Hef5.0weisen · Oct 11, 2011

Yo9u should go through the lines, pop them off and have a look at the o-rings, I imagine they're bad. I was havingthe same problem yrs ago...first line I took off..o-rings were done....got the tool and new o-rings at autozone, cheap.

You say "base"....what one? I'm AF out in Hell, NM...stationed at Cannon...I fly as well.

HISSIN50 · Oct 12, 2011

Pilot, did the shop jump the switch so the compressor cycled?

If pressures were copacetic that way, trace the wiring from the LPCS to the compressor (through the WOT relay). That relay has been problematic for some.

94GTPilot · Oct 12, 2011

Hef5.0weisen said:
Yo9u should go through the lines, pop them off and have a look at the o-rings, I imagine they're bad. I was havingthe same problem yrs ago...first line I took off..o-rings were done....got the tool and new o-rings at autozone, cheap.

You say "base"....what one? I'm AF out in Hell, NM...stationed at Cannon...I fly as well.

I will give them a look. But even if the o-rings are bad, that wouldn't cause the compressor to not kick on, would it?

I'm Marines out of Kingsville, flying the T-45 before follow-on fleet jet. What do you fly??

94GTPilot · Oct 12, 2011

HISSIN50 said:
Pilot, did the shop jump the switch so the compressor cycled?

If pressures were copacetic that way, trace the wiring from the LPCS to the compressor (through the WOT relay). That relay has been problematic for some.

They did that originally to get the compressor cycling and take in the refrigerant. When I took it back originally, I think he tried it again with no success. It's the auto hobby shop on base, which I think is a much better bet than most Midas or Auto Zone shops.

How would I test the wiring? Multimeter? I'm pretty savy when it comes to bolting/unbolting things, but still a tad bit behind the learning curve when it comes to wiring/electricity.

HISSIN50 · Oct 12, 2011

Yeah, a 3 dollar DMM is all that is needed. I used to refer folks to the wiring diagrams in the Wiki but since that thing went away, I need to dig up some old online diagrams.

toyman · Oct 12, 2011

This link may help with the wiring diagrams.

Mustang FAQ - Wiring & Engine Info

Jumped A/C cycling switch... Compressor kicked on. Now what?

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