I just got a 97 F150 4.6l for a work truck and the A/C doesn't blow cold. So far i've tried jumping the pressure switches, swapping the complete HVAC controls from another truck, checked the only fuse under the dash I could find for the a/c and still nothing. I get voltage to the pressure switches but nothing to the comp clutch no matter what I do. If anyone could help with any ideas or a wiring schematic i'd really appreciate it.

 

Here ya go:

1997 F-150 HVAC Schematic.pdf - http://www.bestsharing.com/f/e3w9g312164

If you have voltage at the cycling switch and jump it but still don't have power at the clutch coil connector, you have an open circuit in ckt #347 (BK/Y).

Steve

 

Not to sound stupid but what do you think would be the next step for me to try? I'm not the absolute best with the electrical side of things and don't want to mess anything up. Oh and just to be 100% sure. Is the cycling switch the one on the condenser or the one on the high pressure line? I appreciate the help so far because this has been driving me insane and it's too hot here in Fl not to have a/c.

 

i also, had this problem on my 96 cougar. the fuse was loose in the fuse panel. took it out and bent the prongs a little bit, instead of them being parallel with the fuse, bend them like 5 degrees or less from being straight, then reinstall it, worked for me.

 

I looked in a friend's owner's manual and it showed a fuse under the dash that said a/c and reverse lights among other things and that fuse is good but i went on ahead and bent it like you described just incase. Still nothing though.

 

Do you have freon in the system? and if so do you you have enough in there? The clutch won't engage without enough freon in the system. Of course it could be a bad clutch or compressor.

 

The cycling switch is mounted on the top of the drier/accumulator canister which is mounted on the firewall below the power block that holds the starter relay and the two maxifuses.

If you have power on the RED/YELL wire, that eliminates the fuse, selector switch, and the high pressure cutout switch.

If you jump the cycling switch, that removes the refrigerant (not freon) charge level as a variable.

If you have gotten this far, have power to the cycling switch, have it jumped, and still have no measured power at the clutch connector, my above suggestion still holds.

Again, follow the schematic, it is your road map.

Steve

 

One last question then i'll get to troubleshooting. Can the diode have any effect on my problem? If so where would it be. Thanks for all the help.

 

Sorry, I forgot, no more freon. I'm reeeel old school.

 

Well I finally had the time to mess with the truck again so here's an update. I traced the wires to the comp clutch and found a bad part in the wire and a bad plug. Now I have power to the clutch but it still won't engage so I guess I have a whole other problem on my hands. Thanks to those that helped me figure out the first problem though.

 

Make certain your ground is good.

Verify coil resistance is 3.5 ohms or so.

Check the clutch gap, might be too wide.

Steve

 

Well I just went out and tested the coil and it's roughly 3.5ohms on the old school analog meter. I pushed against the clutch hub and it partially engaged so now i'm a little better off. I've read about the air gap and i'm assuming they are talking about the distance between the outer hub and the pulley itself? If you see this before I search around for an answer can you verify the correct gap and how to fix it if it's wrong? Thanks.

 

Pull the clutch hub off and remove one shim. Ought to fix it.

Steve

 

This may sound stupid but is pulling the hub off is simple as taking out the center bolt? Please excuse the lack of know how here.

 

I'm having a similar issue with my 03 f150. The compressor clutch isn't engaging. Took it to AAMCO for a free A/C Diagnostic. They confirmed that there was no power to the compressor clutch.

Both the A/C Relay and fuse in relay box, and the 1 fuse in the dash mounted fuse panel are all fine. There is an A/C clutch diode in the relay box I'm unsure on.

I've checked the refrigerant level with a gauge, its fine, I've also jumped both high and low pressure switches and still not clutch engagement.

Any suggesstions?

I'm stumped.