A/C went out on my 2012 Fusion last year, 600 miles over warranty and got no help from Ford. This year, I decided to fix it. A lot of Internet experts say it is probably the temperature sensor on a receiver under the dash. I am 95% sure that is not it. My scanner shows an error for the high-pressure switch. Pressure reads ad "499.7" PSIG from the scanner, which I believe corresponds to open circuit. Refrigerant pressure is 90 PSIG static by actual measurement.
Instructions I found for testing it in circuit on the Internet are baloney. The gauge is a 3-wire gauge and is used on a lot of cars, including GM. I pulled one off an old Malibu yesterday for testing. Here are the Ford schematic for my make and model and the inside view of the one I excised from a Malibu:
The chip is labeled MLX12103EB (Melexis?) and is apparently a real number, but I cannot find a real link to its datasheet or pinout. The white wire was added to allow testing to chassis ground -- there are no direct connections to that ground; although, there are some capacitors that connect to it (one is obvious in the picture).
Questions:
1) Does anyone here have access to that datasheet?
2) I have identified the three leads on the Malibu switch as RED/BLK = Signal, GRAY or GREEN (can't tell) as Reference voltage (5V), and BLK as the Return Common. It does not appear to be chassis ground. Are those assignments correct?
3) The signal seems to be a DC voltage from 5V (no pressure applied) to something less than 5V depending on how much I press on the ceramic disk (white thing below the PCB). Is that correct?
4) Some cars have a Shrader valve on the port to which the gauge attaches. The Malibu did. Does anyone know where Ford does that? Haynes' directions say the system must be emptied before changing the switch. The Ford factory switch does have a protrusion to open a Shrader valve, if one is present.
Regards,
John
Instructions I found for testing it in circuit on the Internet are baloney. The gauge is a 3-wire gauge and is used on a lot of cars, including GM. I pulled one off an old Malibu yesterday for testing. Here are the Ford schematic for my make and model and the inside view of the one I excised from a Malibu:
The chip is labeled MLX12103EB (Melexis?) and is apparently a real number, but I cannot find a real link to its datasheet or pinout. The white wire was added to allow testing to chassis ground -- there are no direct connections to that ground; although, there are some capacitors that connect to it (one is obvious in the picture).
Questions:
1) Does anyone here have access to that datasheet?
2) I have identified the three leads on the Malibu switch as RED/BLK = Signal, GRAY or GREEN (can't tell) as Reference voltage (5V), and BLK as the Return Common. It does not appear to be chassis ground. Are those assignments correct?
3) The signal seems to be a DC voltage from 5V (no pressure applied) to something less than 5V depending on how much I press on the ceramic disk (white thing below the PCB). Is that correct?
4) Some cars have a Shrader valve on the port to which the gauge attaches. The Malibu did. Does anyone know where Ford does that? Haynes' directions say the system must be emptied before changing the switch. The Ford factory switch does have a protrusion to open a Shrader valve, if one is present.
Regards,
John