VW TDI forum, Audi, Porsche, and Chevy Cruze Diesel forum banner

1 - 3 of 3 Posts

·
Premium Member
Joined
·
43 Posts
Discussion Starter #1
Please help! I know this is long, but needed to thoroughly explain what I have tested and found.

A/C worked in Feb. Had cool weather for a couple months, then got warm again this week. Ran the A/C but it was short cycling, about 2 secs on 2 secs off.

Hooked up the guages to check the high and low pressures. Static 100 both sides, short cycled too much to really even out running but saw a low of 40 and high of 180.

Then it suddenly stopped cycling, compressor was off, clutch wouldnt engage. Went through the pdf a/c diy found in a thread on here.

I've got 9.5 volts at the compressor harness plug, unplugged. The coil was open circuit, but after taking it off, I found one wire broken off. Soldered it and it was 4.5 ohms, perfect, worked great when 12 volts applied directly. The harness plug, however, got no volts with the coil load applied. Also, I noticed scuff marks on the outside of the coil housing like the hub was rubbing it and it seemed wobbly on the compressor shaft.

Both fans come on with a/c button, fan, and key on. All fuses good, checked with multimeter. Curiously, when the fans are turned off, they come on when fuse 16 is removed.

When I did the pin checks on the FCM, it was good except for ground on pin 6, but that was the only pin with no explanation. Mine was 50 Meg ohms. Might as well have been open. So I don't know what to check that would make that ground turn good. I tried all tests with a new FCM, same result.

I dont have a multimeter with duty cycle, but read 2.5 volts on the white wire of the pressure sensor switch. According to the chart, that seems like a really low voltage for an 85F degree day and 100 static.

With everything back together, the engine running, the clutch still didnt engage, so I applied 12v directly to the compresser at the plug. The clutch engaged, the hub rubbed the coil, spun it and broke the wire again. So I'm going to replace a worn out clutch/coil, but still have the problem of the clutch not engaging.

The best I can gather is the only logic things that can tell the clutch not to engage is a low pressure condition, or ambient temperature below 32. Since the ambient temperature sensor had continuity though pins in the FCM, that is ok. So before I spend money on a pressure sensor is anybody else thinking that's the problem?

Thanks,
Neil
 

·
Premium Member
Joined
·
43 Posts
Discussion Starter #2
Here was the fix:
Noticed there was no pin on the coil to anchor in the notch on the compressor face. Welded a drill bit into the hole where the pin was. Cut it to length and reintalled everything.

Started the car. Put 12 volts directly to the coil plug. Let A/C run for a few minutes to confirm it was cooling.

Plugged the coil plug into harness and crossed fingers. A/C ran great!

No idea why the FCM wouldn't send 12v to the coil before. Hot wiring the coil for a few seems to have cleared the problem.

New problem... need to order a new clutch, but aftermarket compressor isnt coming up in a google search.
8475
8476
 
1 - 3 of 3 Posts
Top