drof

Early this spring the fan went out on my son's truck. He replaced it last weekend now the fan works on hi only. This is probably caused by a bad therminal limiter switch in the restor circuit, but the compressor clutch does not activate when you turn everything on. The #5 switch is good which is the only fuse in the circuit that I see. If it had a freon leak and it drained down is there a presssure sitch that the would keep the AC compressor from kicking in? Need to know before I get a can of R134 and try to charge the system. Any other ideas.

wde3477

Yes, there is a low-pressure switch that activates somewhere in the low-to-mid 20psi range to keep the evaporator coil from freezing up. I'm not familiar with your vintage truck, but it should be located over by the evaporator/drier. Might try short-circuiting the switch to see if the compressor picks up.
Suggest to throw a set of gauges on the system to verify low freon - it is possible to have a plugged metering orifice or other obstruction in the low pressure line to cause low pressure.
If it is indeed low on freon, probably going to need more than one can to get things back up to snuff and to prevent rapid clutch cycling due to low pressure.
There are legal issues with putting freon into a leaking system, but that's up to your conscience.
Another idea is that the compressor clutch itself is not engaging when voltage is applied. Could pull the connector at the compressor to check voltage.

drof

Thanks for the quick reply. First thing I need to do is get the hormones (21)home long enough to check the system. I am the one who picks out the H2O bottles out of the trash to put in the recycle bin so I will watch our enviroment as best as I can.

drof

There is a Y at connector for the blower motor, what should this hook to? This truck is the basic no frills model no power anything. I do not see where the fan resistors are.