A/C question for Ford / Lincoln / mercury experts

Joined
Mar 1, 2002
Messages
3,643
Likes
62
Points
48
Location
Kentucky
#1
http://www24.brinkster.com/sdhartney/linc/evtm,%20eatc.pdf
A/C clutch will not engage, even if I supply power and ground directly to the clutch coil. The coil has continuity, it may be shorted internally. It is not shorted to ground. There is a possibility that the clutch air gap is too wide, I should have tapped on the clutch plate when I had it "powered up" but I didn't think of it at the time.
But this is the main concern...I'm getting no power from the control head or module to activate the coil.
This is a 1997 Lincoln towncar with automatic A/C (eatc). the control head seems to do everything but supply power to the clutch coil circuit.
I hope my link at the top works for you. When I test for power at the cycling switch, I get battery voltage with a DVOM, but not enough juice to power up my trusty test light.
Should I be looking for a harness problem? Customer says it used to work intermittently, but now it doesn't work at all.
Is this a classic control head/module failure, especially if the coil is shorted?
Is there some way to put the system into self-diagnostic mode? Would I need code descriptions?

Thanks for your interest,
Dan Moon
 
Joined
Nov 14, 2006
Messages
2,079
Likes
0
Points
36
#2
If the compresser clutch has power and ground it should kick in.
On the automatic controls there is a self-diagnostic rest.
Does it have a good charge of R-134a?
What are your guge readings High and low side?
 
Joined
Mar 1, 2002
Messages
3,643
Likes
62
Points
48
Location
Kentucky
#3
To be honest, I haven't checked system pressure. Since the system works great when it does work, I'm assuming there is not a problem with the amount of 134a. Even an empty system should have enough juice at the cycling switch to light a 12 volt test light when the system is set to max air on a hot day.

Tell me more about the self-diagnostics. Is there a button-press sequence?

Thanks,
Dan Moon
 
Joined
Nov 14, 2006
Messages
2,079
Likes
0
Points
36
#4
With auto controls system pressure is very important.
High or low pressure can/may shut down controls.

On Lincoln's I have had some weak compressor clutch coils that shut down when hot.
When testing check for 12 volts to the compresser coil when hot and when compressor quits.
If it has voltage to it and ground and clutch kicks out replace coil or clutch and coil.
PDF below on self diagnostic.

[attachment deleted by admin]
 
Joined
Mar 1, 2002
Messages
3,643
Likes
62
Points
48
Location
Kentucky
#5
Thank you crunch, for your input.
I found the reason for "proper voltage, but lack of current" to the clutch coil. There is a mini relay used to feed that circuit on one of the circuit boards that are inside the HVAC control head module. A solder joint failed for one of pins of that relay. I resoldered it, and it's fixed! Customer loves me!

I suspect there will still be a problem with the clutch. It started working after I pushed on the clutch plate...I think the air gap may be a little wide, or the coil is weak. I will let the customer test it later to see if it stops working when the engine is screaming hot.

Dan Moon
 
Joined
Nov 14, 2006
Messages
2,079
Likes
0
Points
36
#6
You are welcome and thanks for the fix post and how it went.

And yes the customer is the best tester. :ROFL
Good luck
Crunch