2003 LX sport. The AC had a good charge, and blows nice and cold once it turns on, but it takes at least 5 min, sometimes up to 15 min to turn on. Once it turns on, it works fine for a while, but sometimes you can feel it turn off. Once its on I would say that its at least 90% functional, but I want it to turn on right away! Its a black car and its HOT! The pressure reading in the ECU is normal, and you can see the ecu command the AC on and off in the datalogs when I push the button. If anybody has any ideas, or wire diagrams that would be really helpful.

Possible clutch ??

PM me your email and I'll send the diagnostic routine from the Ford manual.

I was thinking it might be the clutch, but I'd like to know the output to that little plug on the clutch so I can test it offline before I replace the clutch. The weird thing is that it works after a while, but you don't even see the clutch twitch when you turn the ac on and off.

email sent

I tried to follow a bunch of stuff in that paper, but without a NGS tool, there are a lot of steps that I have to skip. Once the car is hot, everything seems to work just fine. I can turn the ac on and off a bunch of times and it works all the time. I'm thinking about throwing a new low and high pressure sensors at it and hope that it works.

Cheap things to check first:
- wiring/plug at compressor clutch
- plug at cycling switch (on the lo pressure side
- ac relay in the distribution box under the hood

The cycling switch itself is a common cause of ac clutch not engaging. Easy and cheap to replace. Sometimes the wiring to the plug on the switch gets bent/broken and can cause intermittent clutch on/off.

Underhood relays are exposed to heat cycles and can act strange.
Also easy and cheap to replace, common 5 pin relay.

Also, the distance between the drive plate on the front of the compressor and the pulley should have about the clearance of a business card, maybe just a little more. Too little gap and they lightly grind against each other. Too much gap and the clutch has a harder time engaging the drive plate/pulley, sometimes heat expansion after running the car helps to get the pulley to engage more often.

Just some ideas.

^THIS. Switching the relay solved my exact symptoms. Took my car maybe 5-10 minutes to get the AC blowing cold before that. Now its INSTANT, like it should be.

Thanks guys! I've removed the plug at the compressor a ton of times now. I tested the output with a VOM and got no volts when the engine was cold, and 13V when it was hot and the compressor would engage. I thought it was the clutch at first, but when the engine was hot the clutch would turn on and off every time I turned the ac on or off. When it wasn't working, I had my wife rev it to about 2000rpms and then turn it on and it didn't even twitch. A relay does make sense, and I have one in my tool box. Fingers crossed for the easy and cheap fix!

I have been having a similar issue on mine, I keep meaning to double check the pressures, but it sometimes turns on, sometimes doesn't, sometimes works fine, sometimes quits after a while. Weird thing too, cooling fan comes on full force when it stops working, so that makes me think the PCM thinks the pressure is too high at the condenser and cooling it off will fix it. My guess, bad pressure switch maybe if not overcharged? My temperature deal in the HVAC cavity is spot on, checked that with the DMM....

Yours might be a relay, but if it isn't you aren't alone my friend..haha

Larry, mind sending me a copy of that diagnostic as well, I'll PM you my email again if you don't have it from the OASIS report...

It was the relay. I swapped it with the horn relay and the AC works and the horn doesn't. I'm going to upgrade all the small relays. Thanks guys.

Is there a video or photo guide on how to replace AC Relay, and is there any special tools to remove/install relay.

you pretty much just pull it out. then put the new one in. pliers may be helpful, the outer case may pop off, but there should be a bar on top of the internals you can pull it with if that happens.

Is there a photo to show me where this relay is located at on the car

Courtesy of Da Governator
https://www.crownvic.net/drock96marquis

I replaced relay and the AC still blows out congested for awhile before finally kicking in, a guy said it could be a vacuum leak or vent doors. How can I check the vent doors to see?