Damn, I smoked part of my ECM!

[S10xGN]

Hi All,

A few days ago, I got my A/C system working - yesterday, I went out to show a bud how good it worked, and it didn't! The problem was no power to the clutch. In diagnosing where the breakdown was, I mistakenly jumpered (in the relay block) the the power (blu) wire to the A/C clutch control (grn/yel) instead of the clutch (grn). This put 12V to an internal ECM ground circuit. Needless to say. my A/C clutch control line no longer works. In fact, the A/C request line is also dead. Is this repairable? The ECM still seems to work OK, just no A/C. Anyone NOT running A/C want to swap ECM's?

Thanks!

 

[mike85gn]

Red Regal T was selling working units for 45 bucks. Search the parts for sale section for more info. I bought one and was happy with it.

 

[S10xGN]

As a matter of fact, I just bought one of John's ECMs a few weeks ago, and you're right, it is a sound unit. Just venting some frustration on my stupidity...

 

[TurboJim]

The AC request line goes high on AC engage. The switch in the dash sends 12v to the low pressure switch, then to the AC relay. That wire branches off and goes to the ECM as AC request. the ECM then closes the AC clutch relay via gnd which I believe opens a normally closed relay. I gotta look at a schematic, and I dont have one handy. If the ECM wasnt commanding AC, If a pressure switch was open it wasnt commanding AC. I dont think you hurt anything. If it was, does it smell? Like it smoked?

 

[S10xGN]

My mistake, Jim - it was the A/C clutch control line that I stuck 12V to. From what I can tell, this grounds internally whenever the "request" line gets powered (A/C on) which allows the relay coil to "ground" to operate the relay. By sticking 12V to the clutch line with A/C requested, I prolly smoked the clutch control line... It does nothing when I request A/C now. I do have another ECM I'll try this Fri. after work, but if it can be fixed, I'm game!

Thanks!

 

[TurboJim]

Originally posted by S10xGN
My mistake, Jim - it was the A/C clutch control line that I stuck 12V to. From what I can tell, this grounds internally whenever the "request" line gets powered (A/C on) which allows the relay coil to "ground" to operate the relay. By sticking 12V to the clutch line with A/C requested, I prolly smoked the clutch control line... It does nothing when I request A/C now. I do have another ECM I'll try this Fri. after work, but if it can be fixed, I'm game!

Thanks!

Well, guess what you got at the ECM with the relay plugged in? 12v! Although you have the coil of the relay as a current limiter. The only way you might have smoked the ECM is if it was turning on the AC clutch and you hit pin A2 with 12v via a jumper wire (straight copper, no light bulb or resistor.) . The current might have smoked it.

FWIW, I'm looking at a diagram right now.

12V feed comes from the dash AC switch, thru the low pressure switch to pin D of the relay. That pin also send 12v to term B8 of the ECM in the form of an AC request. Pin C on the relay comes from the brake light switch 12v feed. And ECm term A2 is the clutch relay control.

Looking at it, yes, you might have smoked the ECM if your jumper wasnt current limited (a straight jumper instead of a test light etc), but I would also check to see that your brake lights work. Maybe you popped the brake light fuse at some point while testing?

 

[S10xGN]

Yeppers, it's smoked. Put my spare ECM in and the A/C works, so putting 12V to the A/C clutch line is NOT recommended! Oh, well, I've got a spare ECM that works, but not for an A/C car...

Later,