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Static pressures don't match??? I don't get it.

bkbarnes on Sun June 29, 2008 2:57 PM User is offline

Year: 1988
Make: Ford
Model: F150 4X4
Engine Size: 351
Refrigerant Type: R134
Ambient Temp: 90
Pressure Low: 25
Pressure High: 100
Country of Origin: United States

I don't understand my readings for the Statice pressure are 25L/100H I thought they were supposed to be the same. What could cause this? Are my gauges wrong?

chris142 on Sun June 29, 2008 4:27 PM User is offline

ya sounds like your guages are wacky.

GM Tech on Sun June 29, 2008 4:49 PM User is offline

or you are not depressing the valve core when you open them--cheap gages do this...

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

bkbarnes on Sun June 29, 2008 5:41 PM User is offline

Hmmm. I just went out and checked the pressures again, same thing, run ac and low side gauge did not move. Put a differant low side gage on and am getting 26-30 psi R134 and 220psi @ 92ambient/ air is cold. Turned of ac and high and low equalized. Thanks for the help.

Side note. I have the LPCO switch jumpered at the moment cause compressor kept cycling every 5 sec. I suppose I need to replace that and then I should be good?

webbch on Mon June 30, 2008 10:48 AM User is offlineView users profile

I'm not a pro, but I think if the compressor is cycling like that, it does not mean a bad LPCO switch - it more frequently means you are low on refrigerant. That's the behavior I noted in my friend's '93 mustang when it only had 0.2 lbs in (we measured it when we pulled it out). When the compressor engagaged, the low side would drop below the LPCO set point and shut down the compressor. It would repeat this cycle every 4-5 seconds.

parollback on Tue July 01, 2008 7:23 AM User is offline

Sounds like the orifice tube may be clogged. Same thing happened on my 89 Ford F-Superduty. Since you are using R134a in a 1988 truck, did you pull and replace the O-tube when it was converted to 134a?

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