QuestionThe high pressure relief valve blew for the first time. My car is a 1976 Eldorado, 30000 mi, all original.The ac system has functioned properly for years with no oil/freon12 leaks and proper gauge readings. After the blow off, my tester shows no leaks anywhere, but the system sight glass shows foaming and system is barely cooling. What should I check/replace before I recharge and possibly lose R12.
Thanks - Bill
AnswerGEES Bill, Your making me feel older than I want to believe.
OK, Although is a rae that this type of problem occurs on older Cadillacs It does occassionally happen.
If your gages are showing recommended pressures at 1000 rpms in drive of which they should read approx 200 on the high side and 40 on the low side. Rule of thumb is that the high side will be 4 times as high as the low side as said above in relation to A/C gage readings.
There are only a few possible answers:
1. The orfice tube, if applicable, Has a restriction.
2. There is a problem with one or more of the REED VALVES within the A/C compressor.
3. The condensor is not getting adequate air flow thru the vanes due to a possible weak clutch fan, If applicable.
4. The PRESSURE CYCLING SWITCH on the low side of the A/C system is intermittently faulty.
5. The high pressure valve is intermittently faulty.
These are the most common faults and should be easily diagnosed with the use of a manifold set (A/C gages).
I will drag out my older Caddy books and refresh myself of this type of system and get back to you this afternoon if I come across anything I missed and or have made any notations of over the years.
Now that you made me feel OLD, I need a NAP.
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A followup after dragging out my notes and brain cob webs has resulted in whereas your system utilizes a POA valve and an expansion valve.
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