Hi,
I have a 3.9L disco I and I can't get my A/C condenser fans to turn on. I think it is the sensor. I need to know where they terminate at. I have been looking in the rave and at electrical manual k5. But its just diagrams and it doesn't show pictures on the actual truck!
Thanks!!

 

The condensor fans are connected to the same power line as the compressor clutch. When the clutch is engaged the fans come on to change the state of the high pressure gas back to liquid. Is your compressor clutch engageing???? Try bipassing the High pressure switch and low pressure switch seperately to see if the problem is there first. Just jump a wire across the terminals to continue the circuit without the system using the switch's.

 

If they are not turning on, they are dead, pretty common for an old Disco.

 

Look in the tech section for your answer.

 

The RAVE schematic shows a connector for each fan, so you can disconnect those and read with a volt meter. If truck is not cranked, but ignition switch is turned on, and AC is ON with fan in any position, inside blower fan should be running, and you should have 12 volts (more like 13) at the condenser fans. There have been posts about replacing them with salvage yard units, or brand new ones for a certain version of an Asian car (same Denso motor). My copy of the Electrical Troubleshooting Guide has a connector section, which shows pin out of the connector and picture of location. Looks like above fan and slightly to one side of drier. You might have to pull grille to get at it. Old electricians used small nails or straight pin or very sharp probes to meter wire without skinning it back, still good practice to tape up afterward. AC condenser fans should be on (1) whenever AC is on, (2) when coolant is 212F+, or (3) when coolant is 110 C plus fuel temp is 70C plus and engine is off. IMHO #1 is the easy way to test it. Should you end up splicing wires, replacing fans, etc., be dang sure you get the polarity right so that fan DO NOT blow toward front, they need to blow toward radiatior.

 

Thank you all. I checked my voltage and yes I have 13 some volts. I also noticed that when I turned the rover on, with ac on full the left one went spinning at full speed and the right one was a lot slower. I don't think the motors are bad. I think it is a switch. I looked in the rave and it says I must drain the freon out of the "H" so I can check it.. I think I am just going to attempt to jump it.

 

If the clutch wasn't engaging would my A/C still be really cold? I think it is working. How would I know?

 

No you would not have any cold air if the clutch was disengaged. You can see the clutch on the pully side of the compressor. The clutch will not spin if the A/c is off. Sometimes the high or low pressure switch activates and will intermittantly shut down the system to prevent damage. If your system was not working at all, the first thing to check is the clutch engagement and then bipass each switch to determine the condition of the system. This of course is the method if you do not have gauges. If you had a gauge you could read any system over pressure or under pressure. When the A/C system goes bad it can either create a buildup of pressure or decreased pressure based on the system defects. If one of these switch's activated it would shut your system down (disengage the compressor clutch) to prevent further damage.

 

All that was said, plus:

1. You have determined original complaint is OK (fans are coming on - but you will need to deal with slow fan at some point, it will cause poor AC perfromance in stop and go or idle conditions).

2. If you have gauges, great. If not, a household thermometer at the center vent should be in the 40- 45 degree range if you are getting good cooling. If low on freon, may not cool until truck running at highway speed, or may not cool at all (compressor won't turn on). Really need gauges (buy, rent, or borrow).

 

Every vehicle A/C system I have worked on lists the vent temp to be between 25-35*F.