2004 Escalade - Dual evaps; cold rear only
Posted: Sat Sep 24, 2016 12:58 pm
Vehicle: 2004 Escalade
Ambient: 70deg F
Refrigerant: R134
Hi guys...just registered, but I've been lurking and learning for a while. I've been pretty good at diagnosing and repairing issues with my other vehicles, thanks to the info on this forum, but this 2004 Escalade has me quite puzzled right now. This car has two evaporators, one in front, and one in the rear. The only time I get cold air is when both the front and rear are turned on, and then I only get cold air from the rear vents. I've tested the three possible scenarios and taken some readings:
Scenario 1: Front on/rear on, cold from rear vents only
Stable pressures: 35/200 (yes, no compressor cycling for the hour I sat there looking at it, weird)
Minor flutter on the gauge needles
Scenario 2: Front off/rear on, no cold from rear vents
Stable pressures: 70/75, compressor does not turn on (note the high low side @ 70, weird)
No needle flutter
Scenario 3: Front on/rear off, no cold from front vents
10 second compressor cycles. On at 50/120, off at 25/150.
Scenario 3 seems to indicate low refrigerant due to the rapid cycling, but on the other hand, those pressures seem in the right range for the ambient. Am I missing something obvious here? One other bit of information that may or may not be relevant: there is a continuous hissing sound from the area of the accumulator. Not sure if this sound has always been there or not. It is NOT a leak however, as I've injected dye and UVed the area, with a negative result.
Many thanks.
Ambient: 70deg F
Refrigerant: R134
Hi guys...just registered, but I've been lurking and learning for a while. I've been pretty good at diagnosing and repairing issues with my other vehicles, thanks to the info on this forum, but this 2004 Escalade has me quite puzzled right now. This car has two evaporators, one in front, and one in the rear. The only time I get cold air is when both the front and rear are turned on, and then I only get cold air from the rear vents. I've tested the three possible scenarios and taken some readings:
Scenario 1: Front on/rear on, cold from rear vents only
Stable pressures: 35/200 (yes, no compressor cycling for the hour I sat there looking at it, weird)
Minor flutter on the gauge needles
Scenario 2: Front off/rear on, no cold from rear vents
Stable pressures: 70/75, compressor does not turn on (note the high low side @ 70, weird)
No needle flutter
Scenario 3: Front on/rear off, no cold from front vents
10 second compressor cycles. On at 50/120, off at 25/150.
Scenario 3 seems to indicate low refrigerant due to the rapid cycling, but on the other hand, those pressures seem in the right range for the ambient. Am I missing something obvious here? One other bit of information that may or may not be relevant: there is a continuous hissing sound from the area of the accumulator. Not sure if this sound has always been there or not. It is NOT a leak however, as I've injected dye and UVed the area, with a negative result.
Many thanks.
I was indeed missing the fact that the rear system does not operate when the front is off. I had kind of suspected the orifice tube - thanks for the confirmation. Will pull and inspect.