A/C system has zero suction

Tiny
MORGAN8173
  • MEMBER
  • 2011 FORD ESCAPE
  • 2.5L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 160,000 MILES
Replaced compressor, liquid line, accumulator with switch along with expansion valve. System will not charge, typically 1/4 of the bottle of 11oz 134A the clutch will engage and you will then be able to properly pull your high & low readings but it won't engage. So low side 70ish psi with high side barely 50 psi. I even opened the compressor again and dumped the oil. Then read in the event that it had too much oil then pulled vacuumed for nearly 2 hours and tried to recharge it again and it still won't engage.
Sunday, December 29th, 2019 AT 11:21 PM

8 Replies

Tiny
STEVE W.
  • MECHANIC
  • 14,082 POSTS
Was the compressor changed for internal failure? Was the system fully flushed? What happens if you use a jumper from battery positive to the clutch power lead (violet w white stripe) to engage it?
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Monday, December 30th, 2019 AT 2:11 AM
Tiny
MORGAN8173
  • MEMBER
  • 70 POSTS
It was replaced as it was under warranty thinking it had to be the compressor. Honestly probably jumped too fast considering a new compressor didn’t fix the same issue. Yes, it was vacuumed and flushed twice. I will try and run a lead directly to the purple and white wire today to see if it will engage then. If it does what do you suspect? The switch is new along with the connector. If you were to unplug the connector from switch I get an error code right away so I’ve stopped considering that but hey I’m open to whatever test you suggest.
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Monday, December 30th, 2019 AT 2:22 AM
Tiny
MORGAN8173
  • MEMBER
  • 70 POSTS
So I haven't had a chance to remove the cover off the bottom of the engine to access the connector for the compressor but I wanted to confirm with you what the ground reading on the switch connector shooed be? I'm not getting a full 12v it's fluttering around mid 7 to mid 8's and the other ones were pulling neg readings. Could this be the issue right here?
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Monday, December 30th, 2019 AT 12:12 PM
Tiny
STEVE W.
  • MECHANIC
  • 14,082 POSTS
The clutch power is just to determine if it is something mechanical in the system or if it's electrical. If jumping the clutch works and you can charge the system it has to be an electrical issue. Which is very common. Usually a bad connector or ground issue.
The pressure switch yellow w violet wire is signal return aka ground. It should be at zero volts, anything over that and you have a ground issue at either the PCM or one of the other components that share that ground is damaged. That would be the fuel tank pressure sensor or the intake air temperature sensor section of the MAF. The yellow w green wire is the voltage reference for the switch. That wire should have 4.8-5.1 volts on it when you use the yellow violet as the ground. Higher and you have an internal PCM issue or there is a wire connecting to battery voltage through corrosion or?
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Monday, December 30th, 2019 AT 12:49 PM
Tiny
MORGAN8173
  • MEMBER
  • 70 POSTS
Can you confirm the Santech A/C Switch MT0896 is compatible. So as it stands right now this is how I have this switch connector wired.
Black - with green and yellow wire harness.

Yellow - with yellow and purple

Blue - with purple and orange
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Monday, December 30th, 2019 AT 1:04 PM
Tiny
STEVE W.
  • MECHANIC
  • 14,082 POSTS
This is the pinout for the switch. That pigtail is okay for a Ford, as long as the wires are connected to the correct pins.
Yellow with violet is ground.
Yellow with green is 5 volt reference.
Violet with orange is the sensors signal.
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Monday, December 30th, 2019 AT 5:59 PM
Tiny
MORGAN8173
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Upon further checking I didn’t have the ground properly hooked up also noticed one of the pin terminal in the MAF. Connector is popping out of place but I was able to pop it back in but once you unplug it again it’s back out and low and behold it’s the yellow violet wire as well.
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Friday, January 3rd, 2020 AT 10:02 AM
Tiny
STEVE W.
  • MECHANIC
  • 14,082 POSTS
Sounds like the retaining ear on the terminal broke or bent in too far. Not a hard repair with the proper crimp tool. Does it work with the wires correct?
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Friday, January 3rd, 2020 AT 5:03 PM

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