More A/C woes...Help!!!
06-27-2003, 12:57 AM
#16
Instructor
There's a connector next to the compressor that goes to the clutch. Unplug it and check for voltage. Sometimes the connection at this connector is bad. At least you'll know if there's current to the clutch and can eliminate that from the equation.
06-29-2003, 07:10 AM
#17
Dear Randall
Do you know exactly the two conditions or tresholds(temperature, pressure, etc.) for slow and fast condenser fan speed ?
I cannot measure AC pressure, only have a digital termometer.
Is there a simple test to see both speeds coming on ?
Thanks
Herbie
Do you know exactly the two conditions or tresholds(temperature, pressure, etc.) for slow and fast condenser fan speed ?
I cannot measure AC pressure, only have a digital termometer.
Is there a simple test to see both speeds coming on ?
Thanks
Herbie
06-29-2003, 04:20 PM
#18
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Hey Herbie,
There's no threshold for slow-speed condenser fan operation. It should run automatically in slow-speed. If it doesn't, your ballast resistor is probably bad. You can test the condenser fan slow and fast-speed operation in the same way you do the oil cooler fan:
<a href="http://p-car.com/diy/fan/" target="_blank">Oil Cooler Fan DIY</a>
The shop manual text says the condenser fan should shift to second (fast) speed at a high-side pressure of ~19 bar (270 psi). On the other hand, the electrical drawing shows 17.5 for the pressure switch setpoint. Looking at the table for high-pressure vs. ambient temp for an R-12 equipped 964, 17.5 bar first occurs on the high end of the acceptable pressure band between 28 and 29C ambient. At ~40C, the minimum acceptable pressure is only 18.5 bar. So, if the setpoint is 19 bar, it's possible to have an ambient temp of 40C, and still not have the condenser fan running in fast-speed.
In summary, it's possible for the condenser fan to start in fast-speed at an ambient temperature as low as 28C. It's also possible to have an ambient temperature of 40C, and the fan is still only running in slow-speed. I'm afraid you really need the proper pressure gauge to determine if your fan is supposed to be running in fast-speed.
All this said, I think the most important thing--and the most likely thing to be out-of-service--is the condenser fan running continuously with the AC.
<img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
There's no threshold for slow-speed condenser fan operation. It should run automatically in slow-speed. If it doesn't, your ballast resistor is probably bad. You can test the condenser fan slow and fast-speed operation in the same way you do the oil cooler fan:
<a href="http://p-car.com/diy/fan/" target="_blank">Oil Cooler Fan DIY</a>
The shop manual text says the condenser fan should shift to second (fast) speed at a high-side pressure of ~19 bar (270 psi). On the other hand, the electrical drawing shows 17.5 for the pressure switch setpoint. Looking at the table for high-pressure vs. ambient temp for an R-12 equipped 964, 17.5 bar first occurs on the high end of the acceptable pressure band between 28 and 29C ambient. At ~40C, the minimum acceptable pressure is only 18.5 bar. So, if the setpoint is 19 bar, it's possible to have an ambient temp of 40C, and still not have the condenser fan running in fast-speed.
In summary, it's possible for the condenser fan to start in fast-speed at an ambient temperature as low as 28C. It's also possible to have an ambient temperature of 40C, and the fan is still only running in slow-speed. I'm afraid you really need the proper pressure gauge to determine if your fan is supposed to be running in fast-speed.
All this said, I think the most important thing--and the most likely thing to be out-of-service--is the condenser fan running continuously with the AC.
<img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />