A/C Clutch only engages for about 1 minute at engine start

[chrism2097]

I just picked up a 2011 Fiesta recently, and found that the A/C clutch only engages for about 1 minute when you start the engine. After that, the clutch won't engage again unless you turn of the ignition and restart the car. I thought maybe it was the relay, so I swapped the A/C clutch relay with the DRL relay (same relay) with no change in status. I'm thinking that it's a switch or sensor that's failing to send the signal to the relay to close the circuit. Any ideas?

 

[chrism2097]

And yes, I checked all the fuses.

 

[scotman]

So, you are saying that the A/C is not working at all,beyond the momentary keyon cycle? If that's the case, you either have a low level of R134a refrigerant or the pressure switch has failed.
The pressure switch is under the accumulator tank on the lower right side of the condenser. You can see it if you shine a flashlight below the alternator.

 

[scotman]

You cannot just unthread it and screw in another switch. The system is always under very high pressure at this point and it must be evacuated with special equipment and then serviced. This is a job for professional repair shops with the right equipment.

 

[chrism2097]

So, you are saying that the A/C is not working at all,beyond the momentary keyon cycle? If that's the case, you either have a low level of R134a refrigerant or the pressure switch has failed.
The pressure switch is under the accumulator tank on the lower right side of the condenser. You can see it if you shine a flashlight below the alternator. View attachment 4002

Thanks for the info. System is charged. Pretty sure it's the pressure sensor. Would you happen to have a part number? I looked on Rock Auto, but couldn't find it on there.

 

[scotman]

D

Thanks for the info. System is charged. Pretty sure it's the pressure sensor. Would you happen to have a part number? I looked on Rock Auto, but couldn't find it on there.

Ford bluebox number should be 6F9Z-19D594-AA.. should also have a Motorcraft number but couldn't find it quickly.
Just a heads up. You can go into any auto parts store and get a switch for around $25 bucks. But many shops will not install or warranty any customer procured parts. The rise of online parts sales and Chinese junk knockoff parts is the main reason for this situation.

 

[chrism2097]

D

Ford bluebox number should be 6F9Z-19D594-AA.. should also have a Motorcraft number but couldn't find it quickly.
Just a heads up. You can go into any auto parts store and get a switch for around $25 bucks. But many shops will not install or warranty any customer procured parts. The rise of online parts sales and Chinese junk knockoff parts is the main reason for this situation.

Thanks again. I plan on doing the part install myself, but since I don't have a vacuum pump or any way to property evacuate & purge the system, I'll simply have a shop do that part of the job.

 

[chrism2097]

D

Ford bluebox number should be 6F9Z-19D594-AA.. should also have a Motorcraft number but couldn't find it quickly.
Just a heads up. You can go into any auto parts store and get a switch for around $25 bucks. But many shops will not install or warranty any customer procured parts. The rise of online parts sales and Chinese junk knockoff parts is the main reason for this situation.

The refrigerant level was a little low. Likely because when I was doing some testing, and jumpered the connections for the relay, I left the compressor running too long, it built too much pressure and the pressure relief valve allowed some refrigerant to escape. I topped it up so that when the compressor is running for that first 30-60 seconds, it blows cold air. Pressure looks good on both the high (~270psi / it was 95º out) and low (~30psi) sides...so it's not a problem with the amount of refrigerant.

I still want to check whether or not voltage is getting to sent to the compressor after the initial run. I'm not entirely sure how to test the pressure switch. Do you know if it can be temporarily bypassed? I have a friend that does home A/C work, and he said he would help me with recovering the refrigerant & purging the system, should I need to go that route.

 

[scotman]

Just disconnect the the lead to the switch, connect the voltmeter, turn on the A/C and look for it to show that electricity is being delivered to the switch. If you don't have juice, the relay or fuse might not be good. If you get juice and no cycling, you probably need a switch.
I love A/C! I will not tolerate an inoperative system for more than the time it takes to diagnose, order parts and fix it!

 

[chrism2097]

Just disconnect the the lead to the switch, connect the voltmeter, turn on the A/C and look for it to show that electricity is being delivered to the switch. If you don't have juice, the relay or fuse might not be good. If you get juice and no cycling, you probably need a switch.
I love A/C! I will not tolerate an inoperative system for more than the time it takes to diagnose, order parts and fix it!

Thanks again for the suggestions. I tried everything you suggested, and everything else I could think of but still couldn't find the source of the problem. I brought it to a friend that works on A/C systems - he said pointed to an electrical issue, and didn't have the time or expertise to delve into it. I caved and brought it to the shop. Turns out it was the Engine Cooling Fan wiring assembly. Part # WPT1417. Part replaced, and now the air blows COLD.

Technician notes: "Performed wiggle wire test and found fan will come on. Necessary to open harness and find intermittent open in fan circuit. Opened harness, all wires OK. Found fan connector intermittently losing contact causing concern. Replacement of pigtail confirmed problem resolved."

I live in California's Central Valley, where temps regularly reach 105-110 during the day. There was one morning I was driving to work (140 miles r/t) at 4:30am a couple weeks ago, and the temp was still over 90 outside!. Oh well, at least I'll be comfortable commuting now.

 

[Handy Andy]

Good catch!

So in this case, the problem with the cutoff is because of the Coolant Fan having an intermittent contact - so the circuit sense loop on the ECM "sensed" this fault then shuts off AC - so it's a good way to determine the health by such a symptom.

Wow, sorry to see you have such a quirk act up that way.

But it's good to know the coolant fan and the A/C are together - just not the same circuit.