Hey all,<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>
I have a 2007 f250 powerstroke with a dodge 12v and dodge ac compressor utilizing ford pressure switches. My ac clutch in not engaging and I am not getting power to it. So far I determined I have 12v to the low pressure switch. I don’t understand how the high pressure switch works but I have 12 volts on two of the four terminals. From there I am not getting voltage to my compressor wires. On the compressor I know I have a good ground to one wire but no voltage to the other. Is there a way to test the high pressure switch or is there another problem I am not seeing. Thanks for any help. Any test suggestions would be welcomed.<o></o>
I just put the system back together and vacuum evacuated it, added 9 ounces of oil and 2.8 pounds of Freon. The pressure is about 100 psi high and low side at 82 degrees F ambient.<o></o>
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Buy Ford parts and try again. Hopefully you didn't use actual freon

 

R134 don't need Ford parts

 

Are you sure you don't have computerized clima control in 2007 model?
If not -the pressure limit switches need to be both closed for the system to work. Easy to put a jumper on the plugs for testing.

 

I know how to jump the low pressure switch, but I am not sure how to jump the high pressure switch.

 

Ck. fuse F1.17, 10 amp at Battery Junction Box and fuse F2.23, 20 amp Central Junction Box. Both feed the A/C clutch relay mounted in the BJB. The pressure switches and circuits feed the PCM and the PCM in turn controls the relay.

 

Ok, I will have to give that some thought. I don't i checked the 20a fuse yet. Is it possible to have 12v at the high pressure switch on two terminals and still have a blown fuse.

 

The high and low pressure switches do not feed the relay, they are inputs to the pcm. The fuses I mentioned are to power the A/C clutch relay circuits which is controlled by a pcm output. These are two totally different circuits with different fuses.

 

Ok, thanks. I will check fuse 23 tomorrow.

 

All my fuses are ok and I even flip flopped the relay with another one and still no power. Is there a way to test the high pressure switch so I can eliminate that as my problem?

 

The high pressure switch is dual function, one being high pressure cutout and two being fan control. The high pressure cutout side opens at 435-475 and closes at 230-290 psi, circuits RD/YE and TN/RD. Circuits VT and BK/YE are fan control, if I rcall the contact closes at approx 325-350 can't find the spec on this one. Is this manual or automatic climate control.

 

Automatic. Also, the fan operates fine, don't know if that means anything.

 

Speicher,

According to your specifications I don't have enough pressure on the high side to satisfy the switch. I thought the high side pressure goes up when the compressor kicks on?

 

The high-side switch is a safety cutout in the event of over-pressure. In normal operation, the normally closed switch contacts just pass the AC Demand/Request signal through to the rest of the circuit. When the system over-pressurizes, those contacts open to disable the clutch while simultaneously closing the other set of contacts to force fan operation (on vehicles with electric fans).

 

Thanks, that explains a lot. If I test the switch with it removed from the vehicle will I get continuity on any of the terminals?<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>