A/C Help Needed Please

[homermandy]

1998 5.4 Expedition. Just replaced engine and put in new compressor, dryer, condensor, all hoses, etc. The A/C clutch is not engaging. Here is what I have done and found.

There is NO voltage to the low pressure cutoff switch on the accumulator. None. I jumpered 12V to the cutoff switch and then jumpered the 2 wires on the cutoff switch and the compressor engages. So I know the problem is between the control in the dash and the cutoff switch,

I followed procedures in the service manual to check voltage at the switch as well as resistance of the switch. All is good.

But I cannot trace where this wht/red wire gets power from. I checked continuity of all fuses in the cab as well as the power distribution box and all checked out.

Is there a specific relay that would provide power to this switch. It should have 12V when A/C is engaged but it does not.

I am stumped.

Please help.

 

[stamp11127]

Have you checked to see if you have 12v coming out of the function selector switch?
There is a connector C159 located top of fender about mid point driver side that connects the function switch to the high pressure cutout. Wire your interested in is solid pink. From the high pressure cutout it then goes to the low pressure switch as a red/yellow wire.
May be easier to check for 12v at the high pressure switch connector when the a/c is on.
The wiring diagram doesn't show a white/red wire. Where is it connected?

 

[IMINYOURCHAIR]

This file is a printout from the service manual. go to page 75 there and follow the symptom chart. it shows which pins to look at for voltage/resistance fuses etc. I had a problem this morning with the compressor not kicking in but re seating the two switches made it come on..

good luck to you

 

[homermandy]

Thanks for the help. When I replaced the ac lines I left the high pressure cutoff switch off the new piping. Hooked it back in and reconnected the dongle and all is good. Always something small. Thx