Is there a compressor fuse that would keep my compressor from even cycling? What other possible reasons are there for the compressor to not even cycle?

Andy

 

Start by identifying your vehicle and whether or not it has manual or auto climate control.

Low refrigerant or electrical faults are th most common reasons for no A/C clutch engagement.

If you don't have gauges, take it to a shop for a checkout.

Steve

 

It's a 98 F-150 XLT with the normal dash controls. I checked the pressure on the reciever and it was around 85 psi, I think. I did that a couple weeks ago. I'll double check tonight. Even with that pressure, I would think the compressor would cycle for a short time. No cycling. Therefore, I think the compressor isn't getting the power. Any thoughts on that?

Thanks

 

85 psi static is plenty for initial clutch engagement. Depending on the ambient temp, it may or may not be enough for cooling operation if everything else were working.

The electrical circuit is relatively simple:

Fuse F5 in the under dash fuse panel supplies power when the ignition switch is in RUN.

Power is routed to the FUNCTION MODE switch that supples power to the A/C HIGH PRESSURE switch in all positions except OFF, VENT, and FLOOR.

The HIGH PRESSURE switch is normally closed and only opens above 445 psi. Output of that switch goes to the cycling switch. Output os the cycling switch then goes to directly control the clutch.

First, check the fuse. If blown and then reblows, suspect also the blend dor actuator module.

Second, disconnect the cycling switch at the accumulator and jumper the connector to see if the clutch engages. If so, the switch is bad. If not, you'll need a meter or test light to see if power is at the cycling switch and to locate the likely open circut.

Check that, and let us know what you find.


Steve

 

I got a few minutes to check out the situation again. I actually have closer to 110 psi on the accumulator. Fuse F5 was good. I unpluged the cycling switch and jumped it. It sounded like a fan came on or something, but not the compressor. The wire I used to jump was getting rather hot, so there was juice going to it. That's as far as I got. I need to spend some time and just trace the electric cables, but it's going to take quite a bit of time. Thats where I am. Any ideas off that?

Thanks