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A/c compresor not coming on no ground true pcm. It has

Customer Question
A/c compresor not coming...

A/c compresor not coming on no ground true pcm

Mechanic's Assistant: Have you checked the Freon level?

Yes it has around 58 psi i just recharge it w a scale

Mechanic's Assistant: What is the model of your '58 Ford?

Its a 07 ford fusion

Mechanic's Assistant: Are you fixing your Fusion yourself? What have you tried so far?

Im missing grond thru the pcm if i stimulate the grond puting ground wire for 2 seconds it keeps runing by it selft all day long and u can shut it on and off from the inside w out the ground wire and comes on off u let it seat over night wont come on till u stimulate the pcm

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

I replace the evap temp sensor

Submitted: 1 year ago.Category: Ford
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Customer reply replied 1 year ago
no ground coming from pcm
Customer reply replied 1 year ago
i replace the evap temp sensor
Customer reply replied 1 year ago
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Answered in 11 minutes by:
10/27/2016
Ford Mechanic: Juan Crespo, Tech Trainer replied 1 year ago
Juan Crespo
Juan Crespo, Tech Trainer
Category: Ford
Satisfied Customers: 1,532
Experience: A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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Hi there.

What engine do you have on that '07 Fusion? Manual or Automatic A/C? Also, what do you mean by "no ground true pcm", is it that the PCM is not grounding the compressor clutch relay?

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Customer reply replied 1 year ago
07 ford fusion w a v6 automatic yes pcm not grounding compressor clutch relay
Customer reply replied 1 year ago
if i get the wire from the pcm pin 64 and add ground for 2 second like stimulate the pcm the system will star working normal till shut off the car completly and wait next day and no ground anymore
Customer reply replied 1 year ago
the evap temp sensor its like 93degree and the pressure switch its like 58 psi
Ford Mechanic: Juan Crespo, Tech Trainer replied 1 year ago

That sounds like the PCM is not getting an A/C request signal. It's much easier to diagnose this type of issue with a scan tool capable of reading this type of data; do you have access to one of those?

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Customer reply replied 1 year ago
i have an autel and data says a/c its comanded on a/c switch is 58psi temp sensor its 93 psi
Customer reply replied 1 year ago
but says relay its off till i put ground to it and ill take ground out and keeps working on his own
Customer reply replied 1 year ago
i can shut it on and off and works fine
Customer reply replied 1 year ago
can u give me a call at(###) ###-####
Ford Mechanic: Juan Crespo, Tech Trainer replied 1 year ago

All calls carry an extra fee and have to be requested through the site. If you like, I can send you the Premium Offer request. Otherwise we can continue on this chat. How would you like to proceed?

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Customer reply replied 1 year ago
guess we can keep chating
Customer reply replied 1 year ago
anything that u like to now that the scaner would show ?
Ford Mechanic: Juan Crespo, Tech Trainer replied 1 year ago

Not a problem. Just want to remind you that this is not a super fast chat like the ones you might be used to. Since it goes through the site, it takes longer to send and receive messages.

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Ford Mechanic: Juan Crespo, Tech Trainer replied 1 year ago

Can your scanner display WAC and WACF PIDs? If not, look for anything that could be preventing the PCM from activating the compressor, such as any type of engine malfunction, misfire, etc... Then please let me know.

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Customer reply replied 1 year ago
no malfuctions till i not put grown and stimulated the relay wac stay on off positition on scaner
Customer reply replied 1 year ago
the answer is wac says is off and no other engine malfunction car runs good
Ford Mechanic: Juan Crespo, Tech Trainer replied 1 year ago

If the PCM was seeing a request, then WAC should be ON. Where are you seeing the A/C request as being ON? Which PID?

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Ford Mechanic: Juan Crespo, Tech Trainer replied 1 year ago

Also, grounding the circuit manually can damage the driver inside the PCM. I wouldn't do that if I were you...

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Customer reply replied 1 year ago
it says off on less i put ground to it
Customer reply replied 1 year ago
wat should i look for
Customer reply replied 1 year ago
wat else turns a/c on or of
Ford Mechanic: Juan Crespo, Tech Trainer replied 1 year ago

The PCM is the only thing that energizes the compressor clutch relay. It does that upon receiving an A/C ON request from the control panel and after monitoring the enabling signals (TPS, engine temp, refrigerant pressure).

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Ford Mechanic: Juan Crespo, Tech Trainer replied 1 year ago

Most of the times, there is an issue with the pressure transducer connector that interrupts the signal to the PCM. With your manifold gauges attached, the A/C on and the engine running, set your scanner to display the A/C PRESSURE PID. Are both readings the same? If not, check the pressure transducer connector and wiring.

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Customer reply replied 1 year ago
yea but the 58 psi should be plenty off freon to come on? and wen it does run by it selft everything works perfect just that inicial start up
Ford Mechanic: Juan Crespo, Tech Trainer replied 1 year ago

The pressure transducer signal is just one of the enabling criteria the PCM looks at for compressor engagement. So, if the PID has the same value as the gauges, then that signal is OK. Next one to check is Evaporator temp PID. It should read the same as ambient temperature. Does it? If that signal is also OK, then the next one to check would be A/C switch PID. It should show on and off as the switch is turned on and off. If not, then the control head is probably bad (another common problem). If it is also OK, then the next check would entail removing the instrument cluster to test the wire from the control head to the cluster to see if it is OK (since the commands are sent through the CAN, the cluster acts like a body control module that takes the electric signal from the A/C control head, converts it to serial data and then sends it to the PCM through the CAN)

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Customer reply replied 1 year ago
I was earloer working on the car trying to see the data and the car was runing for 5 10min and a/c was on on the controler not the compresor out nowere the compresor came on and starblowing cold i m sure tomorrow in morning its not gona come on anymore till probly warm up
Ford Mechanic: Juan Crespo, Tech Trainer replied 1 year ago

There might be a loose connection somewhere. Please run the checks I outlined for you on my previous post and let me know what you find.

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