Hello All,
I have 1996 Ford Mustang 3.8L engine.
I know the factory a/c compressor just failed. I replaced the compressor, orfice tube, accumulator and flushed system. Evac and recharged system.
The problem now is when I plug the power wire onto the clutch it kicks in for just a fraction of a second and then it looses all power at the plug. This was tested with a test light. The clutch gets its power from the black and green wire and I followed it back to a relay module mounted inside the right front fender. I found the green and orange striped wire supplies the power to the module in the fender and when the clutch is plugged in and I lose power at the clutch the green and orange wire goes very dim. Its obvious to me that i have a voltage drop but im not sure where to look. Is the problem in the module or further back in the system?
I have from time to time used the a/c knowing the compressor was bad, could it have damaged the relay inside the module in the fender?
Thanks for any info.
Fuzzy1

Have you tried another relay? Just the relay - little cube - 5-10 bucks even from Ford!

T
_________________________________________


Tom Greenleaf - MetroWest, Boston
http://acsource.net/acforum/index.php

Product Part No. Price Gp-Sorensen / Relay - A/C Compressor Control
MR76 $9.99

_____________________

There's one from AutoZone. These go like water and this fits the others too,

T
_________________________________________


Tom Greenleaf - MetroWest, Boston
http://acsource.net/acforum/index.php

Relay itself is not replacable. Must replace the whole module which contains the relay you mentioned. A definite cost of more than 10 bucks. Any other areas to diagnose or how can I verify that its the module for the problem described above?

Q: What did you do to keep compressor on for recharging?

Q2: Is LPCO switch sending power thru it? If more than two wires there don't touch it. A/C requested should be two wires when unplugged one has full battery voltage other nothing which sends signal on to relay (if in a module so be it) then on to compressor's clutch coil.

Q3: Is it the same clutch and coil or were they swapped over from old one? If coil checks high ohms (dang me I should know - like over 3??) it could be shutting system down.

Q4: Did you touch HPCO switch at all? They pop modules in one second with improper current or when jumping it is attempted sometimes.

Q5: Does this Mustang use just electric fans or only belt driven - I just don't know what each model might have done.

How much refrigerant by weight is thought to be in this right now?

All questions - sorry,

T
_________________________________________


Tom Greenleaf - MetroWest, Boston
http://acsource.net/acforum/index.php











(This post was edited by Tom Greenleaf on Jun 27, 2008, 7:57 AM)

A1 System took about 1.5 lbs of 134a before I knew there was a problem, as compressor would not engage. I could manually apply 12volts and ground to compressor and force compressor on.
A2 LPCO is good and working properly
A3 The clutch is new, Was attached to new compressor.
A4 No, did not touch HPCO switch.
A5 The cooling fans are all electric and working. High idle also works when a/c request is turned on.
A6 As measured on scale from 30lb cylinder, the system has about 1.5 lb of 134A.

Sounds good with what you've done. Now to find out why it cuts out so quickly. If your weigh in is correct you are still 10oz from the full charge - enough for all kinds of testing and the system should be trying on it's own but lousy cooling with all other things in order.

You said it only engages for a slit second. Can you define that in actual time? The HPCO could detect super high pressure but not all that fast. Also if you can get pressure readings now where the charge level is it would help pin this down.

If HP can jump off the scale that quick it would shut down normally. The electric fans means that the module is involved in decision making for when they should be on based on whether compressor is on. Not sure with each model but more vehicle's are using info from HP switch to engage fans when pressure indicates it would need cooling and shut fans down like when you are flying down the highway and enough air from speed is enough and it saves on the power lost to the fans. Sports cars started doing that trick first.

What's needed now is pressures taken (forced at compressor ok for a short test for this) both high and low.

Also - if you can get an ohm reading between the terminals of the clutch coil. New or not if it is drawing way too much current it's a problem - not high on the possible list but should be ruled out.

Hit back and let's getter going,

T
_________________________________________


Tom Greenleaf - MetroWest, Boston
http://acsource.net/acforum/index.php

Seems my last post did not go through.
Well its now October, customer had to have car since last post in June. Turns out that the problem was a bad low pressure cycling switch on the accumulater.
System is now working great cooling to mid 30's.
Just wanted to finish out this post.
Still want to thank you again for all the usefull info, keep up the good work.
Thanks Fuzzy1