98 Ranger AC Valve Discharges

jbgood · Jun 7, 2008

Hi everyone. I have a 98 Ranger, 2.5L 350,000KM. Just lately my compressor
high pressure valve discharged a couple of times. I never had one ac problem before. Would not the high pressure switch cut out the compressor before that would happen? I did not get any codes and I am going to check the pressures tomorrow. I can rotate the rad fan with some resistance when it is hot so I think that is ok.( Not overheating also) Could a restriction somewhere cause this? Thank you.

jbgood · Jun 8, 2008

A lttle more information today. When the high pressure valve discharged a couple of times, I was at a stop after driving down the highway. Ambient temp today was about 90-95. I hooked up the gauges ;low went upto about 60 , high to about 350. I then doused the condensor with water , went to 35 and 180 right away . I then took a stick against the fan blades at idle and was able to stop it without too much trouble. I still felt some resistance rotating the fan by hand and the engine does not overheat . Does it still sound like the fan clutch? Thanks.

Earl43P · Jun 10, 2008

The high pressure cutoff electrical switch opens at 435-475 psi, disengaging the clutch.
I would expect the mechanical pressure relief valve to be somewhat higher than that.

I've never seen a high pressure relief valve discharge and then "reset" and permit continued normal operation. Once they blow, they're done, in my limited experience.

I suspect you slightly over-serviced it with refrigerant, the fan clutch is weak (fluid leaked out) and the high outside temperature contributed to the problem. If you haven't serviced it lately, belay the over-servicing and OAT.

I'd be interested to know:

Outside air temp
Center Duct outlet temp (fan on med-lo, Norm ac -not recirc or Max, engine at 2000 rpm)
Lo and Hi side pressures under those conditions

and watch for the pressure relief to vent again, at what ? pressure, to confirm/condemn its condition.

Your pressure observations do not indicate any restriction (low side would drop considerably as high side climbs {I've seen the low side pull vaccuum with the low pressure switch jumpered} ).

I too, suspect an ineffective fan clutch for the pressure to hit 350, but it drops when you supercool the condensor.

To me, the definitive test of your fan clutch should occur every morning. Start it and drive away, you should hear the fan at high speed until you get 100 yards or so, then it should get quiet. That is how mine has always operated. It quits about the time I hit 3rd gear.

98 Ranger AC Valve Discharges

jbgood

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Earl43P

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