97 Taurus, no AC, compressor doesn't engage.

1997, GL, SOHC, 3.0L (vulcan I believe), 192000 miles
No cold air from the AC one morning on the way to work so I opened the hood and the compressor is not engaging. Pulley is spinning freely and no odd noises either. I'm ok with no AC, but now when taking off from a stop light or when evening out speed after acceleration, the car chugs and bucks a few times then it's fine. Could the compressor malfunction be causing an intermittent drag on belt? I have to rule out needing a tune up because that was done a couple years ago and I just drove this thing 520 miles round trip with the AC blasting cold air and averaged 29 mpg.

Any help is appreciated.

Jay

Welcome to the forum!

I doubt that the non-functioning A/C is related to the stumble from a stop. I would not rule out an issue with spark plugs, wires, or fuel system just because that work was performed a couple of years ago. If economy parts were used (particularly, plug wires) and/or they were not routed/installed correctly, they could be failing. Similar for the spark plugs, if they are not the OEM style they may have worn faster than desired, it's a rather common issue with waste spark systems. And given the age and mileage of the car, vacuum leaks from brittle/cracked vacuum hoses would not be out of the question. If the Throttle Position Sensor (TPS) is giving an incorrect reading that could cause the stumble too. If it was reading as wide open throttle (WOT) that could explain why the A/C is not engaging, but if stuck at WOT it would also put the car in clear flood mode and probably would not start. Additionally if the Mass Air Flow (MAF) sensor is contaminated it could cause the stumble. This would be especially likely if you or a previous owner had an oiled reusable style air filter installed at one point. There is a MAF sensor cleaner on the market made by CRC that works pretty well for cleaning MAF sensors.

-Rod

Factory Ford parts installed by a certified Ford mechanic at last tuneup and the chugging and bucking turned on like a light switch when the compressor took a dump.

Would unplugging the compressor electrical connections be worth a try?

I'll be doing some visual checks tomorrow and FWIW, there is no check engine light.


Jay

Yeah, since the timing seems too close to be coincidental it wouldn't hurt to unplug the compressor clutch field coil connection and see if that has any impact. Weird.

-Rod

Your common denominator is the CCRM Constant Control Relay Module-- it activates the A/C compressor, cooling fans, and fuel pump...

My money is on it-- I see it cause a/c failure many times-- and it is also probably causing intermittent fuel pump failure...

Some good testing to power in and power out will prove this theory-- but they are both driven by that black box beside the battery!!!

Unplugging the clutch field connector didn't help. Although while doing my visual on the vacuum lines, etc... (all look good). I found the source of an oil leak. It looks like a sensor on the drivers side next to the rear head screwed into the block. I'm guessing oil pressure???

I think I might try the CCRM replacement. What's another hundy thrown at this thing? LOL


Jay

If you use a Constant Control Relay Module (CCRM) for the A/C compressor clutch relay. The CCRM will be mounted on the radiator core support, else there should be a discrete relay in the relay center for the A/C clutch. Also pull the clutch diode and check if there is any leakage.

Your common denominator is the CCRM Constant Control Relay Module-- it activates the A/C compressor, cooling fans, and fuel pump...

Some good testing to power in and power out will prove this theory-- but they are both driven by that black box beside the battery!!!

Good thought on the CCRM. I thought they were no more by 1997, but checking the factory service manual revealed you are correct. The manual says it will be located on the left side of the battery behind the headlight. From the drawing in the manual it appears like it might be sandwiched between the battery and the fender. I still don't really picture it as being the cause of the symptoms described, but if the two issues really are related, that is the likely source. I hope I'm wrong. ;)

-Rod

Gonna try the CCRM on Friday. I will let you guys know. I hate searching these threads and never seeing the fix that worked posted when it's all said and done. Wish me luck tomorrow.


Jay

Sorry it took so long guys. The CCRM fixed the AC problem but it still runs rough with no check engine light. Looking for a fuel delivery problem this weekend. I'll update what I find. Thanks a bunch, I'm half way done fixing it. LOL

Jay

This thing has about got me beat. New fuel filter didn't help and now the damn power steering pump is whining. I think it may be a donation car or out by the road as a "mechanics special". I have just about had it. Gonna look at vacuum leaks and possible TCC issue this weekend, then I'm done. Any one close to me on this forum gets 1st dibs as the new owner.
I'll be back to follow up.

Thanks,
Jay