Air conditioning troubleshooting.

[KyS10]

The AC in my Ty hasn't worked since I bought it a couple years ago. I had planned on removing it. So I was never really worried about it. I have recently change my mind about removing it. So tonight I started trying to find the issue.

The system is fully charged, but the compressor won't kick on. All the other hvac features work as advertised. I checked the fuse and it is fine. I made a makeshift connector to go directly from the battery to the compressor. With it connected, the compressor kicks on and runs. So I seem to have a wiring problem. Is there a common fail point for the wiring to the compressor or do I need to start chasing wires?

 

[Logan]

Re: Air conditioning troubleshooting.

Get a new high pressure switch and you will be golden. It is the sensor looking thing mounted on the accumulator with the pig tail on it. I think they are about $7.

 

[randy merritt]

Re: Air conditioning troubleshooting.

Get a new high pressure switch and you will be golden. It is the sensor looking thing mounted on the accumulator with the pig tail on it. I think they are about $7.

I believe that is the low pressure switch. You can jumper it with a paper clip or wire and see if the switch is preventing the compressor from kicking in. Just undo the connector from the switch, and jumper the connector. If the compressor kicks in with the switch jumped, then triple check that you have the correct amount of freon, if you do, then maybe the low pressure switch is bad.

 

[randy merritt]

Re: Air conditioning troubleshooting.

From the sy/ty CD:

 

[Adam#0213]

Re: Air conditioning troubleshooting.

Sounds like the compressor could be the problem.

 

[NJ93TY]

Re: Air conditioning troubleshooting.

I have the same problem. My pressure switch on the dryer is bad. I will be fixin it tommorow right before I leave for carslile.

 

[Brassmonkey]

Re: Air conditioning troubleshooting.

You say the system is fully charged. What were the pressure readings when you jumped the compressor?

 

[DaveP]

Re: Air conditioning troubleshooting.

The big 91-92 pressure switch never gives trouble. I've never replaced one for being electrically faulty.
The smaller, non adjustable 93-up switch lasts about 7-10 years tops. I've replaced a bunch of 93-up switches that failed electrically.

Here's a quick "place to begin" troubleshooting suggestion:

• Engine running.
• A/C controls in Normal A/C, High blower.
• Jumper the two pins in pressure switch connector:

Does compressor run?

No = there are other electrical problems.​

Yes = Does accumulator, and suction hose get cold immediately?

If yes = Replace pressure switch.​

If No = What is the Low side pressure gauge reading?

If drops below 30psi almost immediately, = Low or non-existant refrigerant charge. Or plugged orifice tube.
If stays above 40-ish indefinitely, and discharge side of compressor HOT to the touch = System overcharged.
​

That's how I begin my diagnosis. Others probably do it differently.

 

[Logan]

Re: Air conditioning troubleshooting.

I believe that is the low pressure switch. You can jumper it with a paper clip or wire and see if the switch is preventing the compressor from kicking in. Just undo the connector from the switch, and jumper the connector. If the compressor kicks in with the switch jumped, then triple check that you have the correct amount of freon, if you do, then maybe the low pressure switch is bad.

Correction, low pressure switch. I just know I have had them die on me a few times and I had the same symptoms. Good catch.

 

[KyS10]

Re: Air conditioning troubleshooting.

Thanks for the replies. Just to make sure I'm doing this correctly, you are talking about the connector pictured below, right? The reason I ask is I used a piece of 16ga speaker wire and connected to two pin holes in that connector together with no results. If that's the correct connector I fear that I may have electrical issues somewhere else. I was really hoping it was going to be an easy fix.

 

[Logan]

Re: Air conditioning troubleshooting.

Yes, you should be able to jump that connector and turn the compressor on regardless of system pressure. If that did not work then you may be on the right track in thinking there is another issue. DaveP's post provides a pretty good flow of diagnosis.

 

[DaveP]

Re: Air conditioning troubleshooting.

The pressure switch in this pic is a 93. This is the switch that I know fails after a 7-ish year service life.

If jumping the connector holes does not make the compressor run, check the following:

Just for the heck of it, there is a natural colored 2-pin connector at the rear of the RH valve cover, kind of under the trans dipstick. It has a black and dk green wires in it. Be sure this connector is intact. It is for the A/C clutch interface between the HVAC harness and the engine harness.
Also check that the two black ground wires to sheet metal ground above the blower case are intact. One of these is for the clutch.

With system in Normal A/C, engine idling, any blower speed:

• Check lt green wire at pressure switch connector to ground with VOM. Should be 12 Volt. If = no, there is a control head problem.
• Jump 12 volts from battery to dk green wire at pressure switch connector. Compressor should engage. If = no, jump 12 volts to dk green at compressor clutch connector, clutch should engage. If = no, check black clutch wire for continuity to ground. If still = no, clutch is bad.
• If the above checks out, substitute a known-good relay for the a/c clutch relay. This relay is over the brake booster, has 3 green wires, and one pink wire. It is next to the fuel pump relay, on the same bracket.

If you still can't get the clutch to engage, report back,and we'll go over the circuitry that controls the relay.

 

[DaveP]

Re: Air conditioning troubleshooting.

Just to make sure I'm doing this correctly, you are talking about the connector pictured below, right?

Part of "correctly" are the following:

• Engine running.
• A/C controls in Normal A/C, High blower.
• Jumper the two pins in pressure switch connector:

Getting a good contact in the connector holes is sometimes a little fussy. But 16ga should work pretty well.


The engine MUST be running. In a SyTy, the clutch is ECM-controlled, and the ECM will not engage the clutch at 0 RPM.

 

[KyS10]

Re: Air conditioning troubleshooting.

Thanks again for the advice. The AC is working now and, as usual, it was something easy that I should have noticed earlier. I was running through DaveP's diagnosis steps when I noticed that one of the pins for compressor clutch was bent. I straightened it out and the AC kicked on and ran as advertised. The only issue now is, when the clutch is engaged and spinning, there is a pretty bad rattling sound coming from it. I'm guessing this means I just need to replace the clutch.