I have a 1999 Tahoe with rear air. I replaced the compressor, dryer and orifice tube about 1 year ago. I flushed all tubes and the evaporator at that time. Everything was working well until about a month ago. I noticed that on very hot days the truck would not cool very well. Looking under the hood I noticed that the clutch is not cycling but will disengage when the AC is off. I put gauges on it and with the engine off the High side is at 70 and the low side at 72. With the engine running and AC on, the High side is 140 and the Low side runs at 120 with fan on low and climbs up to 200+ with fan on high. If I disconnect the cycling switch for just a second and plug it back in the clutch stays off until the low side hits about 70 and then engages the clutch. I can see Freon passing through the sight glass on the gauge. The line where the orifice tube is, is cold on the drier side and warm on the condenser side. Ambient air temp is ~75, vent air is ~45. On hot days (90+) the vent air is cool but not cold. Any ideas of what might be the problem? The compressor is about a year old and was new not rebuilt but is not a name brand.
99 Tahoe AC Low Side Very High, High Side Low
- Thread starter mpag
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99 Tahoe A/C low side very high, high side low
I have a 1999 Tahoe with rear air. I replaced the compressor, dryer and orifice tube about 1 year ago. I flushed all tubes and the evaporator at that time. Everything was working well until about a month ago. I noticed that on very hot days the truck would not cool very well. Looking under the hood I noticed that the clutch is not cycling but will disengage when the AC is off. I put gauges on it and with the engine off the High side is at 70 and the low side at 72. With the engine running and AC on, the High side is 140 and the Low side runs at 120 with fan on low and climbs up to 200+ with fan on high. If I disconnect the cycling switch for just a second and plug it back in the clutch stays off until the low side hits about 70 and then engages the clutch. I can see Freon passing through the sight glass on the gauge. The line where the orifice tube is, is cold on the drier side and warm on the condenser side. Ambient air temp is ~75, vent air is ~45. On hot days (90+) the vent air is cool but not cold. Any ideas of what might be the problem? The compressor is about a year old and was new not rebuilt but is not a name brand. It was purchased from Cool Air Parts.
---------- Post added at 08:05 PM ---------- Previous post was at 07:22 PM ----------
Sorry for the double post. I did not realize it had been moved.
I have a 1999 Tahoe with rear air. I replaced the compressor, dryer and orifice tube about 1 year ago. I flushed all tubes and the evaporator at that time. Everything was working well until about a month ago. I noticed that on very hot days the truck would not cool very well. Looking under the hood I noticed that the clutch is not cycling but will disengage when the AC is off. I put gauges on it and with the engine off the High side is at 70 and the low side at 72. With the engine running and AC on, the High side is 140 and the Low side runs at 120 with fan on low and climbs up to 200+ with fan on high. If I disconnect the cycling switch for just a second and plug it back in the clutch stays off until the low side hits about 70 and then engages the clutch. I can see Freon passing through the sight glass on the gauge. The line where the orifice tube is, is cold on the drier side and warm on the condenser side. Ambient air temp is ~75, vent air is ~45. On hot days (90+) the vent air is cool but not cold. Any ideas of what might be the problem? The compressor is about a year old and was new not rebuilt but is not a name brand. It was purchased from Cool Air Parts.
---------- Post added at 08:05 PM ---------- Previous post was at 07:22 PM ----------
Sorry for the double post. I did not realize it had been moved.
SunlitComet
OBS Jedi-Do Good
Uh first off close the valves on the gauge set. have them both open to seen freon in the sight glass just lets it bypass the orifice tube. That would give you a reading like you have now. If still the same then your high reading is low and the low side is high almost as if there is no restriction that would be caused by an installed orifice tube or possibly a txv valve stuck open on the rear evap.
Duh
. Thanks SunlitComet for catching that. Ok with valves closed ambient temp 70 and humidity 72%: With engine off or started and A/C off, the low side is 80psi and the high side is 75psi. With A/C on high the low side is 44psi and the high side is 165psi which looks right. The vent temp is 55 degrees and the clutch is engaged and not cycling. If I momentarily disconnect the cycling switch the clutch disengages and reengages at 60psi and stays engaged, does not cycle.
---------- Post added at 12:09 PM ---------- Previous post was at 10:53 AM ----------
Ambient is 78 now and I checked things again Low Side 52 High Side 180 and vent air temp is 60 degrees.
. Thanks SunlitComet for catching that. Ok with valves closed ambient temp 70 and humidity 72%: With engine off or started and A/C off, the low side is 80psi and the high side is 75psi. With A/C on high the low side is 44psi and the high side is 165psi which looks right. The vent temp is 55 degrees and the clutch is engaged and not cycling. If I momentarily disconnect the cycling switch the clutch disengages and reengages at 60psi and stays engaged, does not cycle.---------- Post added at 12:09 PM ---------- Previous post was at 10:53 AM ----------
Ambient is 78 now and I checked things again Low Side 52 High Side 180 and vent air temp is 60 degrees.
SunlitComet
OBS Jedi-Do Good
With the first set of data your pressures should have been 228/34 psi at 54°. Were you running the engine at 1500 rpm when you got those numbers? I am guessing not. What is the temp like on the rear system? I am worried that the compressor may be a bit weak giving you those numbers but the temps are pretty much on target.
Thanks for your help and wisdom SunlitCommet. I retested at 1500 RPM. Ambient temp 70 degrees, Humidity 59%, front and rear A/C on High. Low side is 40 psi, High Side is 215 psi, Front vent temp is 60 degrees and rear vent temp is 52 degrees.
Clutch never cycled off. If I momentarily disconnect the cycling switch the clutch disengages and re-engages when the pressures reach Low-70, High 130.
Clutch never cycled off. If I momentarily disconnect the cycling switch the clutch disengages and re-engages when the pressures reach Low-70, High 130.
SunlitComet
OBS Jedi-Do Good
Pressures are better but the front temp is still a bit high. You absolutely sure you evacuated before recharging the system and charged it from a state of vacuum? In other words you did not release the vacuum before putting ****** in?
Yes, I pulled a vacuum of 30+hg and held that as I started recharging the system. It has not been recharged since and was working good up until a month ago when it got very hot here in NC and I started to notice it not cooling as well and the clutch not cycling. On very hot days (90+) the vent air is much warmer, cooler than ambient but not as cold as in my other cars.
Is it normal for the small amounts of Freon that come out of the gauge set after removal to be very oily? Wondering if there might be too much oil in the system.
Is it normal for the small amounts of Freon that come out of the gauge set after removal to be very oily? Wondering if there might be too much oil in the system.
SunlitComet
OBS Jedi-Do Good
It might be barely a visible amount if any at all. But if it looks like it could drip off onto a piece of paper after removing it then that might be a bit much. How much did you use?
I had to recharge it twice as I had a blow out because the High Pressure Switch spring clip was not properly seated and blew out of the compressor after initial replacements and charging.
First charge after compressor & accumulator replacement and flush:
Added 2oz to new compressor – the same amount that drained from old compressor
Added 2oz to new accumulator
Added 3oz during recharge process assuming that is what was flushed from the front evaporator.
Assuming that there was still 1oz in the condenser and 3oz in the rear evaporator which were not flushed the total in the system should have been 11oz
Second charge after HPS blowout:
Added 2oz to compressor and 3oz during recharge
I discharged a couple quick shots of refrigerant from the yellow hose on the gauge set into a bottle while the A/C was running and it left a good amount of oil in the bottle.
First charge after compressor & accumulator replacement and flush:
Added 2oz to new compressor – the same amount that drained from old compressor
Added 2oz to new accumulator
Added 3oz during recharge process assuming that is what was flushed from the front evaporator.
Assuming that there was still 1oz in the condenser and 3oz in the rear evaporator which were not flushed the total in the system should have been 11oz
Second charge after HPS blowout:
Added 2oz to compressor and 3oz during recharge
I discharged a couple quick shots of refrigerant from the yellow hose on the gauge set into a bottle while the A/C was running and it left a good amount of oil in the bottle.
