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Old 06-23-2015, 04:45 PM   #1
weshallscrimp
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2002 SC2
Default SC2 with no A/C

We're getting into summer on Long Island, and I'm trying to troubleshoot my dead A/C. Before I take it to my mechanic, maybe someone here has the answer.
  • When I turn on the A/C, the compressor clutch does not engage, and the vents blow uncooled air.
  • First I recharged the refrigerant to the recommended pressure, but the clutch still didn't engage.
  • I verified that the A/C relay is good by swapping it with the fog lamp relay. They are the same Tyco 5170 relay.
  • I verified that the A/C fuse is good.
  • I pulled the relay and shorted the terminal with a wire. The clutch DID engage, but it still does not blow cool air.

Now I am stumped. Maybe the system leaks so badly that by the time I shorted the A/C relay terminal, the pressure was too low. Also, I read about the cycling switch sometimes failing, but honestly I couldn't find it.

Thanks for reading... Any thoughts?
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Old 06-23-2015, 04:56 PM   #2
BV22
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Default Re: SC2 with no A/C

There is a wealth of information on a/c systems and servicing them on this site. You can search and read until your eyes bleed if you are so inclined. But to cut to the chase, if you "charged" the system with one of those cans with a gauge from the parts store, you may not have charged it enough, regardless of what the gauge said.

When the a/c system pressure gets too low due to a refrigerant leak, a pressure switch interrupts the power to the compressor. The setting is around 40 psi. So with the compressor not running, you have to get past 40 psi (in the high zone on that single gauge) before the compressor kicks on, after which the low side pressure will start to drop as more refrigerant is added.

The S series system holds 24 oz of R134a. On a summer day, it takes around 8-9 oz in the system before the pressure is high enough for the presssure switch to close and the compressor to start running. Once running, pressures are to be measured at 2000 rpm engine speed, not idle, and it is best to use a real gauge manifold with high and low side gauges - these can be rented from the parts stores.

Bottom line, you do have a leak somewhere in the a/c system. UV dye was put in the system at the factory, and a UV pen light is a great way to find the leak.
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Old 06-23-2015, 05:19 PM   #3
weshallscrimp
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Default Re: SC2 with no A/C

Thanks for the quick response!

A few followup questions:
  • I didn't know that there is UV dye from the factory. Very interesting. But my car rolled out of Spring Hill over 13 years ago. Do you think the dye would still appear at the point of the leak? If so, I'll get my hands on a UV light.
  • There is plenty R134a left in the bottle. I can try again, this time having someone holding the throttle at 2k RPM, with the A/C on. Of course, the compressor won't be turning while I charge the system. When there is sufficient pressure, will I see the clutch engage automatically?
  • Lastly, the refrigerant I bought says it "seals A/C leaks". Is that BS?
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Old 06-23-2015, 05:25 PM   #4
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Default Re: SC2 with no A/C

Quote:
Originally Posted by weshallscrimp View Post
Thanks for the quick response!

A few followup questions:
  • I didn't know that there is UV dye from the factory. Very interesting. But my car rolled out of Spring Hill over 13 years ago. Do you think the dye would still appear at the point of the leak? If so, I'll get my hands on a UV light.

  • There is plenty R134a left in the bottle. I can try again, this time having someone holding the throttle at 2k RPM, with the A/C on. Of course, the compressor won't be turning while I charge the system. When there is sufficient pressure, will I see the clutch engage automatically?

  • Lastly, the refrigerant I bought says it "seals A/C leaks". Is that BS?

1. The dye lasts forever.
2. Once the pressure rises enough to close the pressure switch, the compressor will engage on its own.
3. Leak sealer does not work and can harm variable displacement compressors like yours. Don't put any more of that in. Get a can of plain r134a.
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Old 06-23-2015, 05:33 PM   #5
weshallscrimp
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Default Re: SC2 with no A/C

Then my work is cut out for me. Thanks again for taking the time to share your knowledge.
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Old 06-24-2015, 08:34 AM   #6
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Default Re: SC2 with no A/C

The UV light is a great diagnostic tool, even if you are going to have someone else do the work. At least you walk in knowing what is wrong. It is best to look for leaks at dusk or in a closed garage. Places most likely to leak are the high and low service valves, the suction hose connection at the compressor, the discharge hose connection at the compressor, and the compressor itself (look at the underside with the UV light and a mirror). The dye stains are greenish yellow. Look at the underside of one of the service valve caps and you will likely see the color you are searching for.
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Old 06-24-2015, 03:27 PM   #7
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Post Re: SC2 with no A/C

Those cans can work if you have a small leak. But if the leak is great enough to disengage the compressor it's less likely to be successful. At that point you have more than a slow leak assuming the system worked the previous season. Additionally a large leak can also introduce air which must be pumped out of the system before charging. Any repairs require the same. You can't add refrigerant on top of air.

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