Air conditioning

Tiny
BANJOBOB1200
  • MEMBER
  • 1997 FORD MUSTANG
  • 3.8L
  • 6 CYL
  • 2WD
  • 150,000 MILES
Car sat 2 years. Broke blower housing while cleaning out mouse nest. Replaced housing. Tried A/C but no cold air. Compressor cycled rapidly. Let idle for about 20 minutes and compressor cycle stopped. Tried jumping low pressure switch (LPS)but no success (later had a better jumper and it worked) never found high pressure switch. Replaced A/C relay in CCRM. Pulled vacuum and it held for 1 hour. Jumped LPS and installed 1 can 134a. Low pressure line got cold but couldn't get 2nd can to go into system-2nd can never got cold. Obviously not an A/C guy! Help!
Saturday, June 20th, 2020 AT 1:47 PM

25 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

I need the high and low side readings for the ac system. that will help me determine the issue.

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

You can rent a set of gauges at a parts store or buy a chap set at Harbor Freight.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

Roy

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Saturday, June 20th, 2020 AT 2:51 PM
Tiny
BANJOBOB1200
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Hey Roy, low side is 90 psi and high side is 85 psi. I initially assumed I was out of 134 and pulled a vacuum. I never tried to evacuate the system (didn't really know how). Could it be that the system was fully charged and I overcharged it? Since starting, I have been given access to a Freon collection system and I could certainly evacuate the system and charge again. Thanks.
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Saturday, June 20th, 2020 AT 6:53 PM
Tiny
ASEMASTER6371
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Those pressures indicate there was Freon in the system.

If the compressor was engaged, the compressor is no good.

If the compressor was not engaged, then you have an electrical issue with the compressor circuit.

Was the compressor clutch engaged?

Roy
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Sunday, June 21st, 2020 AT 4:11 AM
Tiny
BANJOBOB1200
  • MEMBER
  • 23 POSTS
Compressor clutched after I changed the relay in the CCRM. With the low pressure switch jumped, clutch engaged constantly. With low pressure switch installed, clutch engaged at a regular, short interval. Could excess r134 cause system to not cool? (Because I initially added one 12oz can). Thanks. Won't be able to work on it until tomorrow just answering your text. Thanks again.
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Sunday, June 21st, 2020 AT 10:45 AM
Tiny
BANJOBOB1200
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That's "worked" not "clutched" in first sentence.
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Sunday, June 21st, 2020 AT 10:46 AM
Tiny
ASEMASTER6371
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Okay, just to be clear, the readings on the high and low side were when the clutch was engaged?

Roy
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Sunday, June 21st, 2020 AT 10:50 AM
Tiny
BANJOBOB1200
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I'm not sure. I was trying to add r134 and the clutch was cycling. The upper radiator hose burst and I closed all valves and those were the last readings I got. Never had that happen before; what a mess and very thankful for safety glasses!
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Sunday, June 21st, 2020 AT 11:22 AM
Tiny
ASEMASTER6371
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Okay, I need to know if the clutch was engaged.

If it was, you have a bad compressor that is not building pressure.

If it is not then you have an electrical issue turning on the clutch that we need to trace out.

Roy
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Sunday, June 21st, 2020 AT 11:26 AM
Tiny
BANJOBOB1200
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So do I need to hook up gauges tomorrow and record pressure during clutch cycling? In other words record pressures with the clutch turning and record pressures when clutch isn't turning? There should be a difference right?
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Sunday, June 21st, 2020 AT 2:33 PM
Tiny
ASEMASTER6371
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Correct.

Do those checks and post them here for me to view.

Roy
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Sunday, June 21st, 2020 AT 2:36 PM
Tiny
BANJOBOB1200
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Okay, will do tomorrow, thanks.
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Sunday, June 21st, 2020 AT 2:38 PM
Tiny
ASEMASTER6371
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You are welcome.

Always glad to help.

Roy
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Sunday, June 21st, 2020 AT 2:40 PM
Tiny
BANJOBOB1200
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Hey Roy, emptied manifold and before starting car or A/C the static pressures were lo-17/hi-21. Warmed car up and pressures were lo-29/hi-325 with clutch running. After warming up the clutch engaged constantly-no cycling on and off. Anything else you need and thanks again.
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Monday, June 22nd, 2020 AT 8:58 AM
Tiny
BANJOBOB1200
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Before car warmed up the clutch would cycle. The last reading with clutch cycling was lo-22/hi-270.
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Monday, June 22nd, 2020 AT 8:59 AM
Tiny
ASEMASTER6371
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The low side is the issue. 22 is too low. It should be 25-30 rock solid.

I would replace the expansion valve and the dryer and then evacuate for 1 hour and charge the exact amount of Freon needed.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

It takes 34 ounces.

Roy
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Monday, June 22nd, 2020 AT 9:10 AM
Tiny
BANJOBOB1200
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Okay. Why, when it stopped cycling did the low go up to 29 and the hi go to 325? Also, the expansion valve is the orifice tube isn't it?
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Monday, June 22nd, 2020 AT 9:46 AM
Tiny
ASEMASTER6371
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That is correct. It is part of that line. Any parts store should carry that line.

Roy
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Monday, June 22nd, 2020 AT 10:01 AM
Tiny
BANJOBOB1200
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Like the 1st question, any idea why when the clutch remained engaged, it went to 29 lo and 325 hi. Thanks again and I'll be getting a dryer and hose with orifice tube.
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Monday, June 22nd, 2020 AT 10:08 AM
Tiny
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It could be overcharged. The expansion valve flow is minimal and allowing a back up of pressure.

Roy
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Monday, June 22nd, 2020 AT 10:11 AM
Tiny
BANJOBOB1200
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Okay thanks. Will order tube and dryer online and text the results. Thanks again.
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Monday, June 22nd, 2020 AT 10:18 AM

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