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Its the high pressure switch(in wiring diagram), Black/white wire is a Ground, red/yellow wire runs to the next pressure switch, low or cycling pressure switch, then a black/yellow wire from that switch runs to the PCM, pin 86
When both pressure switches pass the Ground to PCM then when you turn on AC that Ground is used to close the AC compressor clutch relay.
If clutch doesn't engage at all then that high pressure switch could be bad, if it cycles on and off then could be low on "Freon" or there is a blockage causing too high a pressure in the system
Switch can be changed without "opening" the system
If its a blockage you can "exploded" a line/connection or ruin compressor, if you bypass the switch, i.e. ground it manually
Best would be to get pressure gauges to test system
This has been a chronic problem from just before my meltdown with the timing chain. I went to a mechanic to troubleshoot when it was still running.
I had the guy vacuum test my system. It took three hours, but it was good to go on that. I also had a switch (might have been the HP switch) replaced because that's what he thought, too.
The refrigerant was recharged back then, too. I rechecked it, and the pressure is still good as of last weekend.
I get super cold A/C when I ground the wire because the clutch now turns the compressor.
I'm thinking I should change the LP switch (and old connector, too...corrosion from being exposed for over a year) just for fits and shiggles
Last edited by cliffdog2004; Apr 19, 2019 at 01:32 PM.
My problem is a little different, but since Ron D. is on the case i will hijack this post.
My compressor gets power to engage but sticks at anything above 60 degreees outside, If i smack the clutch with a screwdriver handle of something it will engage for awhile but sticks again after a few miles or cycles. i've cleaned up the clutch with brake cleaner and compressed air that helped a little but it still does it.
I have a bid of about 800 to replace the compressor as evidently they don't make a clutch replacement kit.
For anyone's info, the part numbers for these switches are YH592 for the canister mount and YH1705 for the compressor mount.
Local parts places have generics for cheaper, but a 90-day warranty is typical.
These stock Motorcraft lasted almost 15 years on my rig. That's for me.
*edit*
YH592 fits:
2001-2003 with 4.0L SOHC
I only noticed this because it was next to my engine...check to make sure it's also for yours
1997-2000 with 4.0L OHV
A lot of the 2.3L and 2.5L
Even the 3.0L. Pretty common over all of Ford.
YH1705 fits:
2001-2011 with 4.0L SOHC
Double check this too for these.
Up to 2011 with 2.3L
A lot of the 2.5L
3.0L too, but double check.
I can only confirm my 2003 4.0L
Last edited by cliffdog2004; Apr 22, 2019 at 09:52 AM.
...cleaned out (as best I could) where is slips into, and put it all back together.
Went back for vacuum test and recharge...
Cold A/C again
Only took me a year
This is why I ALWAYS tell people to put gauges on a system before adding refrigerant (freon, as you call it). Either put gauges on it or take it to someone who knows what they are doing. Too many people think because it's cycling on/off, or because the evaporator freezes, or because they aren't getting cold air, that they need to go to autozone and add the 12 oz can of refrigerant into their system to "hotfix" it. Gauges first, always. A restriction in your system will show on the gauges. I work residential AC, if you post your pressures here I can tell you straight away what's going on.
Its the high pressure switch(in wiring diagram), Black/white wire is a Ground, red/yellow wire runs to the next pressure switch, low or cycling pressure switch, then a black/yellow wire from that switch runs to the PCM, pin 86
When both pressure switches pass the Ground to PCM then when you turn on AC that Ground is used to close the AC compressor clutch relay.
If clutch doesn't engage at all then that high pressure switch could be bad, if it cycles on and off then could be low on "Freon" or there is a blockage causing too high a pressure in the system
Switch can be changed without "opening" the system
If its a blockage you can "exploded" a line/connection or ruin compressor, if you bypass the switch, i.e. ground it manually
Best would be to get pressure gauges to test system
Can I tap my ground wire from my efan to this pressure switch so it switches on when i turn the AC on? If so which wire from the pressure switch (balck & white or red & yellow)?
