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#4459411 - 07/14/17 03:22 PM 1993 Ford E350 A/C Not Cooling
NibbanaBanana Offline


Registered: 05/23/16
Posts: 292
Loc: New England
I have about 60psi of static pressure in the system. When I turn the ac on, the clutch engages but quickly cycles off at 85psi high side, 26psi low side.

I jumpered out the two pin pressure switch so that the ac clutch remains engaged. The pressures are 90psi high side and 14psi low side with the compressor operating continuously. This is the first time I have worked on ac. I would interpret this as both a bad pressure switch and low refrigerant. Does anybody have any other ideas?

The ambient temperature here is about 62F.

Thanks.


Edited by NibbanaBanana (07/14/17 03:23 PM)
_________________________
1993 Ford E350 5.8L, 68K
2002 Ford E150 4.2L, 85K
2006 Chevy Aveo 1.6L 215K
2013 Kia Reo 1.4L, 101K
7500 OCI, M1 5-30 winter, M1 10-30 summer

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#4459418 - 07/14/17 03:31 PM Re: 1993 Ford E350 A/C Not Cooling [Re: NibbanaBanana]
Nukeman7 Offline


Registered: 09/23/06
Posts: 237
Loc: Virginia, USA
The pressure switch is good and shutting off at low pressure to protect the compressor from damage. You are clearly low on Freon and need a recharge. Try adding a 12 oz. can of refrigerant (R-12 I suspect) to see if that will raise it up to maintain low side pressure in the 25 to 30 psi range when the compressor is running steady.


Edited by Nukeman7 (07/14/17 03:34 PM)

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#4459449 - 07/14/17 03:57 PM Re: 1993 Ford E350 A/C Not Cooling [Re: Nukeman7]
Linctex Offline


Registered: 12/31/16
Posts: 6148
Loc: Waco, TX
Originally Posted By: Nukeman7
Try adding a 12 oz. can of refrigerant (R-12 I suspect)


I think the 93's were R-134a?
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#4459454 - 07/14/17 04:02 PM Re: 1993 Ford E350 A/C Not Cooling [Re: NibbanaBanana]
Chris142 Offline


Registered: 06/05/03
Posts: 16812
Loc: Deplorable in apple valley, ca
Whats your ambient temps? high side should be around 2x ambient temps. if its 90F high side should be around 180ish...sounds like its real cold or nearly empty.
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#4459482 - 07/14/17 04:37 PM Re: 1993 Ford E350 A/C Not Cooling [Re: NibbanaBanana]
FSully1 Offline


Registered: 11/22/14
Posts: 45
Loc: Florida
Search out the leak, you're under charged.

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#4459488 - 07/14/17 04:47 PM Re: 1993 Ford E350 A/C Not Cooling [Re: NibbanaBanana]
mk378 Offline


Registered: 09/27/15
Posts: 1414
Loc: USA
"Nearly empty" is a much better description of this situation than "undercharged". If it has worked properly recently, it has sprung a rather large leak.

The rapid cycling is normal when nearly empty. Do not jump the switch. It will start to cycle normally once charged.

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#4459519 - 07/14/17 05:38 PM Re: 1993 Ford E350 A/C Not Cooling [Re: NibbanaBanana]
NibbanaBanana Offline


Registered: 05/23/16
Posts: 292
Loc: New England
The ambient temp is 62F. It has been converted to 134a according to a sticker under the hood but was originally R12.

I put very few miles on the vehicle and rarely ever use the ac. Maybe once every year or two. (I know that I should use it more.) The vehicle is 24 years old so I'm not sure if it's leaking fast or if it has just slowly leaked over time. I bought it 7 years ago and I'm not sure the ac worked all that well when I got it but I had other things to worry about. It is a 14 passenger bus that I built into a camper. We had a very hot spell last summer and now the wife wants the ac working for our vacation this year.

I already added 1 large can of refrigerant before I got my manifold gauges to try to diagnose the problem. It has a rear unit so takes a lot of refrigerant.

So, the pressure switch turns the compressor off when the pressure is too low. Does it also do the same when the pressure is too high?

Thanks.
_________________________
1993 Ford E350 5.8L, 68K
2002 Ford E150 4.2L, 85K
2006 Chevy Aveo 1.6L 215K
2013 Kia Reo 1.4L, 101K
7500 OCI, M1 5-30 winter, M1 10-30 summer

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#4459525 - 07/14/17 05:49 PM Re: 1993 Ford E350 A/C Not Cooling [Re: NibbanaBanana]
bullwinkle Offline


Registered: 10/09/04
Posts: 7652
Loc: Cincinnati, OH, USA
Originally Posted By: NibbanaBanana
The ambient temp is 62F. It has been converted to 134a according to a sticker under the hood but was originally R12.

I put very few miles on the vehicle and rarely ever use the ac. Maybe once every year or two. (I know that I should use it more.) The vehicle is 24 years old so I'm not sure if it's leaking fast or if it has just slowly leaked over time. I bought it 7 years ago and I'm not sure the ac worked all that well when I got it but I had other things to worry about. It is a 14 passenger bus that I built into a camper. We had a very hot spell last summer and now the wife wants the ac working for our vacation this year.

I already added 1 large can of refrigerant before I got my manifold gauges to try to diagnose the problem. It has a rear unit so takes a lot of refrigerant.

So, the pressure switch turns the compressor off when the pressure is too low. Does it also do the same when the pressure is too high?

Thanks.
No, it is only a low side switch, which opens on pressure drop. If your gauges have a temperature scale, a decent starting point is the pressure which corresponds with 45F, as the system gets colder it will drop. In my experience the R134A adapter fittings are a common place for leaks.
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#4459539 - 07/14/17 06:05 PM Re: 1993 Ford E350 A/C Not Cooling [Re: NibbanaBanana]
mk378 Offline


Registered: 09/27/15
Posts: 1414
Loc: USA
Yes especially if you have a tall aluminum adapter fitting on the low side. Those are junk. NAPA may still sell the yellow steel ones that are much better.

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#4459674 - 07/14/17 09:09 PM Re: 1993 Ford E350 A/C Not Cooling [Re: NibbanaBanana]
Chris142 Offline


Registered: 06/05/03
Posts: 16812
Loc: Deplorable in apple valley, ca
Originally Posted By: NibbanaBanana


So, the pressure switch turns the compressor off when the pressure is too low. Does it also do the same when the pressure is too high?

no. Most r12 systems did not use a high pressure cut out switch. If the shop did the conversion correctly they should have added one.
_________________________
02 Wrangler durablend 10w40
87 F250 traveler 15w40
04 Tahoe super-s 10w30
Z400 castrol T 10w40
Can am maveric edge 5w40
57 case tractor 15w40

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