Intermittent No A/C

PC

Full Member
Joined
Sep 3, 2007
Messages
144
Points
18
Make
Ford
Model
Fusion
Year
2012
Miles
85K
Engine
2.5
2012 Fusion manual hvac intermittent no a/c, clutch not engaged. Most times nice and cold, no pattern, sometimes it works sometime it doesn't. Internet search shows evaporator temp sensor common problem with these Fords. I didn't get any codes either. Is there any way to test this other than jumping the compressor. Thanks.
 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
7,234
Points
63
A voltmeter with long leads, back-probed into wires/connectors along the circuit, is the quickest and surest way to tell where the problem is.
 

grcauto

Hero Member
Joined
May 29, 2014
Messages
857
Points
28
2012 Fusion manual hvac intermittent no a/c, clutch not engaged.
Since we know it works when the compressor works we need to focus on the relay and pressure sensors as they are the main things that can cause this type of intermittent problem.
 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
7,234
Points
63
Sorry, but no. We can not dismiss wiring, connectors, and the compressor clutch (both electrical and mechanical. Even the PCM/BCM is a possibility (unlikely, but possible).
 

grcauto

Hero Member
Joined
May 29, 2014
Messages
857
Points
28
Sorry, but no. We can not dismiss wiring, connectors, and the compressor clutch (both electrical and mechanical. Even the PCM/BCM is a possibility (unlikely, but possible).
Relay is very likely as well as pressure switches. Wiring is a possibility of coarse but these are the most common. Next after them is a module problem but they are much more likely to be permanent problems and not intermittent.
 

brcidd

Hero Member
Joined
Nov 16, 2006
Messages
277
Points
18
Next time clutch is NOT turning when it should be- find a hammer handle and tap on front of clutch. See if it engages....if so, your clutch air gap is too wide. Seen it hundreds of times- mostly on GM trucks, low mounts. Sometimes, just hitting a good bump on road or slamming the hood jarrrs it into action. As coil gets warm, resistance goes up and the magnetic field decreases. Answer is to pull off clutch drive and remove fattest shim and replace clutch. clutch gap should be that of a business card
 

PC

Full Member
Joined
Sep 3, 2007
Messages
144
Points
18
This gets more interesting. Started this morning, engine cold, ambient probably 80F, no A/C, ambient air from vents. As engine came to operating temp. vents blowing full heat, temp control had no effect. No A/C all day, started up this evening, A/C nice and cold. Any ideas? HVAC control head? Should I disconnect battery and reboot the PCM?
 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
7,234
Points
63
" No A/C all day, ...."

During that episode, was the compressor ever turning??? (The compressor, not just its drive pulley)

If the compressor was not turning, then you need to get out there (when it isn't turning) and do voltage checks with a meter. Are you ready for that?

If the compressor was turning, then it is time to trouble-shoot the refrigeration system. Most folks start by using a UV light to check for obvious leaks, if none then then add a bit of refrigerant to see if cooling improves; kind of a "Hail Mary" play.

If no joy with that, or if there are indications of leakage, then you will need to pull a vacuum to verify there is a leak, fix the leak, vacuum again, then charge with the specified amount of refrigerant.

Still no joy? Now, with no leaks and a known correct refrigerant charge, you can use high/low gauges to analyze what component in the system isn't working properly. Trying to use gauges without either a known-good system or a system with known-proper charge is meaningless
 
Top