A/C Help
- Thread starter DMZ20
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DMZ20
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No, my truck doesn't have a tach. If that is the way it is supposed to work I am fine with it. Just didn't know if the compressor wasn't kicking on for some reason at low RPM's.
VAL
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You might want to put a e-fan on the condenser, it usually helps.
highdesertrange
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with 134a you need a fan on the condenser when you are not moving. 134a is not as efficient and it really shows up when there is no air flow over the condenser. highdesertranger
lusktommy
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just a random thought....might try a idle kick up solenoid..that usually came on Factory A/C Square Bodies....but yours is an 87 so idk if you could it being TBI
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You just would use a small pusher fan. But in my opinion, an add-on fan is sort of a bandaid fix. It's true that there is probably a lack of air flow through the condenser at idle, but it's most likely because of a restricted condenser and/or a weak fan clutch. I would definitely replace the fan clutch first, as well as making sure the truck idles fast enough.
oneluckypops
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The suggestions that you have already received are very good assumptions and more then likely spot on. But the FIRST thing you should consider doing is hooking up to a set of gauges and check to see what your pressures are reading.
Next you need to actually check the airflow thru the condenser, The easiest way to do this is with an inferred thermometer. Measure the temperature at the inlet fitting of the condenser and then measure the outlet fitting of the condenser. The ideal readings should be between 20-40* differences.
If your readings are higher then 40* then that means your condenser itself has a blockage allowing the refrigerant to stay in the condenser to long. To fix that I highly recommend replacing the condenser, orphus tube as well as flushing the rest of the system.
If your readings are less then 20* difference then that means your airflow is insuffient thru the condenser and not allowing the refrigerant to cool enough. Now the cause of this could be either the idle is too low, or the fan clutch is not working correctly. The easiest way to check is to have some one raise your idle speed to around 1000 rpm's and re test. If your readings are still to low then I would recommend changing or at least adding an auxiliary electric fan.
The condenser in these trucks are designed for R-12 systems, and are honeslty to small for r-134a if you could find an aftermarket condenser that is bigger then you would be able to cool more efficiently.
First lesson in A/C work is temperature=pressure.
Next you need to actually check the airflow thru the condenser, The easiest way to do this is with an inferred thermometer. Measure the temperature at the inlet fitting of the condenser and then measure the outlet fitting of the condenser. The ideal readings should be between 20-40* differences.
If your readings are higher then 40* then that means your condenser itself has a blockage allowing the refrigerant to stay in the condenser to long. To fix that I highly recommend replacing the condenser, orphus tube as well as flushing the rest of the system.
If your readings are less then 20* difference then that means your airflow is insuffient thru the condenser and not allowing the refrigerant to cool enough. Now the cause of this could be either the idle is too low, or the fan clutch is not working correctly. The easiest way to check is to have some one raise your idle speed to around 1000 rpm's and re test. If your readings are still to low then I would recommend changing or at least adding an auxiliary electric fan.
The condenser in these trucks are designed for R-12 systems, and are honeslty to small for r-134a if you could find an aftermarket condenser that is bigger then you would be able to cool more efficiently.
First lesson in A/C work is temperature=pressure.
Last edited:
chengny
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My air blows cold when the engine is at higher RPM's, but at idle blows warm. What could be the issue?
It is usually not so much a refrigeration cycle issue as it is a control problem - specifically loss of proper pressure (vacuum) within the interconnecting tubing.
While it is true that a marginally functioning system can pull the cabin down quicker at higher engine speeds, a system in good shape doesn't need that.
All the dampers, doors and louvers in these systems are dependent on a good source of vacuum to move (and keep them) to the desired position. In the case of warm air issuing from the vents at low engine RPM, the blend door is most likely drifting away from the heater core opening.
As the vacuum generated by the intake manifold falls off, the diaphragm that positions the blend door is no longer able to maintain a tight seal at the heater core outlet. This allows very hot air to enter the stream of cold air that is flowing from the evaporator.
In addition, the force/pressure of the hot air trapped in the hot side of the plenum works on the blend door and tries to "fling" it open.
The climate control panel valves stay steady. So consequently, when the engine speed increases and vacuum returns to normal - the various dampers move back to their proper position.
Long story short, before doing any major repairs to the refrigeration portion of your climate control, it is a good idea to thoroughly inspect all your vacuum hoses.
Pay particular attention to the runs on the engine side of the firewall. They take a beating from heat, oil, grease, vibration etc. and after 23 years don't hold a vacuum as well as they did when new.
It is usually not so much a refrigeration cycle issue as it is a control problem - specifically loss of proper pressure (vacuum) within the interconnecting tubing.
While it is true that a marginally functioning system can pull the cabin down quicker at higher engine speeds, a system in good shape doesn't need that.
All the dampers, doors and louvers in these systems are dependent on a good source of vacuum to move (and keep them) to the desired position. In the case of warm air issuing from the vents at low engine RPM, the blend door is most likely drifting away from the heater core opening.
As the vacuum generated by the intake manifold falls off, the diaphragm that positions the blend door is no longer able to maintain a tight seal at the heater core outlet. This allows very hot air to enter the stream of cold air that is flowing from the evaporator.
In addition, the force/pressure of the hot air trapped in the hot side of the plenum works on the blend door and tries to "fling" it open.
The climate control panel valves stay steady. So consequently, when the engine speed increases and vacuum returns to normal - the various dampers move back to their proper position.
Long story short, before doing any major repairs to the refrigeration portion of your climate control, it is a good idea to thoroughly inspect all your vacuum hoses.
Pay particular attention to the runs on the engine side of the firewall. They take a beating from heat, oil, grease, vibration etc. and after 23 years don't hold a vacuum as well as they did when new.
