Air Conditioning problem
2002 Questions for all other cars V8 Two Wheel Drive Automatic 135889 miles
2002 WORKHORSE STEPVAN / MORGAN OLSON BODY
This is a unform delivery van, similar to the old Chevy P30 step vans. Had a complaint of A/C not cooling well; checked and found 75 deg vent temp at max a/c setting and low speed fan. Compressor running all the time, doesn't cycle on/off either at idle or at 2,000 rpm. Low pressure reading was 45-50 psi with a rapid needle flunctuation; the high pressure was 290 psi steady. Checked the heater core to be sure it was shut off during a/c operation; inlet hose temp was 155 deg. And outlet hose temp was 95 deg. The heater and evaporator cores are housed / mounted together and the fan pulls air through them; the evap. Core was full of dust so I split the two cores, combed the evap core fins and blew compressed air through both of them to make sure they could pass air OK. Have done all this and still only get 75 deg. Vent temp.
High side a little high what is ambiant air temp? Heater core have manual shutoff valve? if not sure blend door is working to route air to evap. bypassing core? does box look like this?
August, 19, 2009 AT 5:32 AM
Ambient air temp was around 92 deg. The heater core is controlled by the OEM valve but the inlet hose temp was approx. 155 deg. And the outlet hose temp approx. 95 deg. So the valve was working. Hard to tell from pic if it's representative of what I have. Both heater & evap cores are mounted together inside box (evap core is mounted nearest air supply side and heat core is mounted between it and fan) and fan is mounted on suction side and pulls air through evap core first and then heater core.
August, 19, 2009 AT 8:29 AM
Print diagram and enlarge. Look at #8 check operation of blend door. Think heater core is getting hot and warming air that would account for highside being elevated. If heater core had no flow then how did temp drop 60deg passing through?
August, 20, 2009 AT 6:46 AM
Enlarged diagram but it blurrs so much that when I print it it blurrs too much, can't bring it into focus enough to read. Rechecked the truck, blend door is closing properly. Has dash-operated heater control valve and valve is working properly; truck came back from 8 hour route and I checked the core port temps. The inlet port coming from the engine was 155 deg and the outlet port was 95 deg with the dash switch set on full cold; when I set the switch on full hot both ports went to approx. 155 deg. I set the switch on cold and within five minutes the inlet was back to 155 & the outlet had gone to 95; I believe the outlet temp is staying around 90 or so degrees because the ambient air temp was 92-94 deg with a heat index of 101 deg plus the underhood temps were high. With the switch on cold the vent temp was 75 deg and temp went to approx. 145 deg with the switch set on hot. The low side pressure reading was 45-50 psi and the high side pressure 245 psi. I forgot to take a pic of the box setup; will get that today & send to you.
August, 20, 2009 AT 8:35 AM
After truck sits say several hours and you start up turn Ac on does it start out blowing cooler air. Then gets warmer the longer it runs? Does system have an accumulator? Lower pressure cutout switch? Start up cold with gagues see if low side goes lower and the more you run the higher it gets. Is force of air flow out vents a little weak?
August, 20, 2009 AT 8:14 PM
I'll have to check the cold startup operation Saturday; trucks run 5 days a week and leave around 5AM. Truck has a receiver/drier and a low side cutoff switch. Vent air flow is good, no obstructions that I can see or tell of.
August, 26, 2009 AT 6:30 AM
AC blows out same degree air (75 deg) after sitting overnight or after reaching operational temp (192 deg). Checked the gauges w/ cold engine & the low pressure reading was same as warmed up. System has dryer & low press. Cutout switch.
Read temps with laser heat gun at different hose locations; approx. 184 deg out of compressor & going into condenser - 125 deg out of condenser & going into dryer - 134 deg out of dryer & 125 deg. Into evap. Core - 126 deg out of evap. Core & 167 deg going into compressor - compressor not cycling at idle.
Not as familiar with expansion valves as I am with orifice tubes; I'm guessing either expansion valve and/or dryer is causing vent temp to stay high.
August, 26, 2009 AT 8:13 AM
That was the result I was looking for TXV not closing orifice size to drop pressure in evap. Recommend TXV and receiver/dryer. Same temp in and out evap is the clincher.