How to test if A/C LOW PRESSURE SWITCH is faulty?

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illriginalized
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How to test if A/C LOW PRESSURE SWITCH is faulty?

Post by illriginalized » Tue Apr 02, 2013 2:15 am

Cable that plugs into A/C LOW PRESSURE SWITCH @ Accumulator was tested with a meter for voltage, mechanic showed me that it wouldn't light up his meter, thus no power was being sent to the A/C LOW PRESSURE SWITCH @ accumulator, thus A/C clutch would not engage unless jumping the relay @ fuse/relay box. Once engaged, ice cold air would blow through, once jumper is removed, A/C goes back to outside temperature.

I'm not sure where to go with this. I'm not trying to replace everything A/C related. I've already swapped the A/C relay with horn. Hit horn to verify that A/C relay is still good. But with horn relay attached to A/C port, the clutch still didn't activate.

So I'm left with a cable/plug/ that is pretty much dead and not sending power to the A/C LOW PRESSURE SWITCH.

So my question is two fold:

A/C LOW PRESSURE SWITCH, how do you know it's faulty?

Has anyone ever had no power coming through the cable that attaches to the A/C LOW PRESSURE SWITCH? If so... how do I trace it? At what point is it common for power to be cut off and never reaching that cable/plug?

illriginalized
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Post by illriginalized » Tue Apr 02, 2013 4:44 am

In our vehicles (in this case 2004)

Does the Clutch relay (inside of the fuse/relay box under the hood) connect to both the A/C clutch and the Low cutoff switch?

Then from the cutoff switch to the A/C and Heat control panel (via blue/orange cable)?

I have a feeling that the cable from the control panel in the dash that connects to the cutoff switch is damaged and I may need to run a wire using inline wire connectors on both ends.

I'll try again but tonight I was trying to jump the connector that connects to the Low cutoff switch but couldn't tell if I was getting cold air (it's cold tonight), so I'll wait til' tomorrow when it's warm out.

If the jumper doesn't work, doesn't this mean that the power coming from the A/C and heater control panel in the dash isn't powering up the cutoff switch?

While jumping the clutch relay (via battery) located in the fuse/relay box under the hood, powers up my A/C and blows cold air.

Thus eliminating:

1. a faulty relay / fuse in the fuse/relay box (relay / fuse is able to send power to clutch)

2. a faulty A/C clutch (clutch activates manually via jumping relay box)

3. lack of A/C freon (blows cold air when clutch activates)

4. a faulty compressor (blows cold air when clutch activates)

5. a faulty cutoff switch (cutoff switch doesn't activate when jumping the connector)
Last edited by illriginalized on Tue Apr 02, 2013 2:55 pm, edited 1 time in total.

illriginalized
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Post by illriginalized » Tue Apr 02, 2013 12:09 pm

BUMP!

illriginalized
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Post by illriginalized » Tue Apr 02, 2013 2:56 pm

BUMP!!!

Does the Blue/orange wire connect directly to the A/C control panel or does it connect to the Evap probe?

I'm getting confused by the stuff I'm reading and this wire diagram:
Image

According to the diagram.. the A/C - Heater Control connects directly to the A/C Low Pressure Switch via Blue/Orange wire.

Is that not correct?

illriginalized
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Post by illriginalized » Tue Apr 02, 2013 7:26 pm

Well then... I guess this forum is no help regarding A/C and wiring.

Thanks anyways.

occasional demons
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Post by occasional demons » Wed Apr 03, 2013 12:10 am

Not too many mess with the A/C. You just have to be patient, and wait until someone has the time and/or knowledge to come along. We all have lives, or are busy with other things...

Image

Basically the PCM controls the grounds to all the relays, based on the inputs given to it. If it doesn't sense every parameter needed, it will not power the compressor clutch.

I believe the BD/Orange does not actually have any real voltage/amperage going through it. I know it will not light a test light, but the completion to ground will engage the compressor via the PCM.

I used that wire to switch the compressor off in defrost mode, for winter use, after the windshield had been cleared. It is a very convenient way to do it without destroying the HVAC controls, and is easily reversible.
Bill
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2001 Neon ES MTX with '02 R/T PCM
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illriginalized
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Post by illriginalized » Wed Apr 03, 2013 12:36 am

Hm..

Well today I tried jumping the Lower Pressure Cutoff Switch using a paper clip on the connector (female) but that still didn't activate the A/C (cold air). I then used an inline wire tap to connect it to the back of the HVAC controls (specifically the dark blue / orange wire for A/C) to bypass anything in between the accumulator's LP cutoff switch. Still didn't get A/C to engage (blow cold air).

I then attached the blue/white wire part of the connector to ground, still nothing.

I tried tracing the pair of wires (dark blue / orange and dark blue / white) which went from the area of the accumulator to the front, right next to the passenger side head lamp where it looks like it grounds.. but to confirm I opened up the heat shield to discover two black wires :shock:

As of now.. the only way I can activate the clutch and get cold air is by jumping the relay.

I may go as far as to have both the low pressure and high pressure switches replaced with a evacuation + recharge.

After that.. if it doesn't work, I'll probably just perma-jump the relay, and attach a on/off switch on the other end where I will mount the switch somewhere on the dash.

I can't afford to spend $300+ for a mechanic to hunt down the wiring to find where the loss of power is. I tried that for a good hour and it's too tedious and waaay too tight in the engine bay.

illriginalized
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Post by illriginalized » Sun Apr 07, 2013 12:50 am

Well went with the relay jump mod. Quick and easy. A/C turns on at an instant. Installed switch:

Image

Extreme ice cold by the way, it's awesome, just have to leave the blower on low, then hit the switch after 10 minutes of the A/C blowing.. then takes like another 10-15 minutes for the A/C to start blowing warm air again, then hit the switch again haha.

Also the mod turns on the A/C fan too.. so A/C turns on @ the fly.

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