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Randall C
Randall C, ASE MasterTechnician
Category: Ford
Satisfied Customers: 12744
Experience:  35 years ASE Master Tech, Diagnostic , Electrical Specialist
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No power to the low pressure switch 05 expedition

Customer Question

No power to the low pressure switch 05 expedition
Submitted: 1 year ago.
Category: Ford
Expert:  Virtual Wrench replied 1 year ago.

Hi,

Is there power at the high pressure switch. Power comes from HP switch and to the low pressure switch. See diagram below

Click here

Let me know please

Customer: replied 1 year ago.
No power at high pressure switch
Expert:  Virtual Wrench replied 1 year ago.

be right back

Expert:  Virtual Wrench replied 1 year ago.

See if you have power coming from Pin #19 on the powertrain control module.

Customer: replied 1 year ago.
If it's the middle connector on the PCM pin 19, I have 12 votes
Customer: replied 1 year ago.
Facing te mounted PCM, what connector is it?
Expert:  Virtual Wrench replied 1 year ago.

Hi,

Does this have auto temp control or manual temp control?

Customer: replied 1 year ago.
Manual
Expert:  Virtual Wrench replied 1 year ago.

Thanks, ***** ***** see what i can find. Be back soon

Expert:  Virtual Wrench replied 1 year ago.

Here is what i can come up with. #19 is the tan/light green wire.

Click here

Customer: replied 1 year ago.
12 volts on pin 19. Continuity good from plug to switch but when connected no voltage at plug
Expert:  Virtual Wrench replied 1 year ago.

If you unplug the pressure switch is there power at the Tan/Lt Green pin?

Customer: replied 1 year ago.
No power at the plug! Went back and checked the PCM power again aNd it's 12 volts. Continuity good
Expert:  Virtual Wrench replied 1 year ago.

That wire goes straight from the PCM to the switch,,,,i'm stumped :-(

Customer: replied 1 year ago.
Exactly!
Expert:  Virtual Wrench replied 1 year ago.

I will see if anyone else has ever came across this before because it sure isnt making sense to me..good luck bud.

Customer: replied 1 year ago.
Thanks
Expert:  Randall C replied 1 year ago.

Hello, new expert here, The system is not setup with power from the PCM to the pressure switches persay, Hard to explain but the PCM is only reading pressure switch grounding, both switches, Power is not going to be present at either switch, It flows through small sensor on the HVAC case called the de icing sensor, so,, may I ask what is the problem at hand? why are you asking the question? what is not working and what all has been done? performed? thanks

Customer: replied 1 year ago.
No Ac
New compressor freon enough to trigger clutch.
Diode good and relay good left front.
By pass low switch,
nothing.
Expert:  Randall C replied 1 year ago.

remove the AC relay.any teminals have 12 volts

Expert:  Randall C replied 1 year ago.

did you bypass both high and low switches

Customer: replied 1 year ago.
both switches
Expert:  Randall C replied 1 year ago.

still need the volt test at relay

Customer: replied 1 year ago.
12 volts
Expert:  Randall C replied 1 year ago.

how many? 1?2?3? I am trying to gather as much informatiin as I can, Not being there.thanks

Customer: replied 1 year ago.
Next to the diode, I has 12 volts
Expert:  Randall C replied 1 year ago.

ok, you may be misunderstanding, Remove the AC relay , Turn key ON< probe the terminals the relay plugs into, How many terminals have power? is this what you did and only one does?Its the 5 prong relay

Customer: replied 1 year ago.
5 prong but 4 active plugs. 2 has 12 volts
Expert:  Randall C replied 1 year ago.

ok, good, now jump 30 and 87, I have diagram link included. Key ON, what does compressor do>? BTW: what are the freon pressure readings with engine off

Customer: replied 1 year ago.
Compressor activates
Customer: replied 1 year ago.
80 and about 70
Expert:  Randall C replied 1 year ago.

little low, is this with engine not running? if so. jump relay and get pressures up some maybe? 8 oz +/- you need to be around 100 both high low engine off. OR 45 low 200 high as an average only

Customer: replied 1 year ago.
Running at this point is 60 200
Expert:  Randall C replied 1 year ago.

ok, pretty close, like low side a bit lower but close., so,, the system does work, I assume you swapped relay? you have power to relay as needed, NO power goes the either switch, is does NOT work that way. so, need to locate the de icing sensor on front side of the HVAc case, unplug, turn key on, how many wires have 12 volts? see the link

Customer: replied 1 year ago.
None but rechecking.
Customer: replied 1 year ago.
1 has 12 v
Expert:  Randall C replied 1 year ago.

well, all I can say is... here is the diagram. "B" shown on the right is power to that sensor., That sensor controls a "GROUBD" to both switches. NOT 12 volts, The PCM reads a ground connection and controls the AC relay on the left side of the diagram, You seem to have everything so,, possibles are. icicng sensor is bad OR PCM is bad

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