A2 pin out for A/C clutch control

[Kevin Jones]

Cannot get a decent voltage to the A/C clutch, diagnosing so far it's down to the gn-ecu not grounding the compressor relay signal at term A2, I cant see anywhere in tuner studio to see if it has an option that has to be activated. Is there a workaround or am I overlooking something?

 

[Kevin Jones]

anything odd here? I cant see anything in a setting that would stick out

 

[EricM]

The settings are all correct. Also notice there is a 5 second delay before it will kick on the compressor, after the AC is turned on. You can set the compressor delay to 1 second for now while you're troubleshooting.

First,
Make sure the ecu is receiving the AC request from the climate control. That signal is 12v and comes into B8 at the ecu. The compressor will not come if the ecu never receives that signal.

You can watch it come on if you look at the "Inputs-Outputs" tab at the bottom. "Digital Switched 12V IN" is what the input is called. So if B8 receives 12v, you should see that input come on. See pic below.

 

[Kevin Jones]

Thanks Eric. Will diagnose, just appears that the relay up by the heater box that A2 should be a ground to complete the circuit but I could be misinterpreting that whole thing at this point.

 

[EricM]

The ECU won't ground A2 to turn on the compressor, until it knows you turned on the AC. So that's why we need to check the AC request first.

 

[Kevin Jones]

B8 is hot at all times even with AC off, diagnosing control module issue.

 

[EricM]

If B8 has 12v, then you should see the input in the software. Is it saying it's on? (Digital Switched 12V IN)

 

[Kevin Jones]

Bad transistor in board up by heater box

 

[Kevin Jones]

Ok, misdiagnosed. Will stay on as depicted in your picture but only with the relay disconnected. With relay connected, will stay on until the 5 or so second cycling and then flashes to 12v off momentarily then comes back on after. 12v positive coming from A2 with it on, will not engage clutch. High current out 2 is on is as is PWM2

 

[Kevin Jones]

is a2 grounded inside ecu or sent out as a ground through another line?

 

[EricM]

It grounds inside ecu, but that is also to the engine block.

So is the compressor cycling on and off?

 

[Kevin Jones]

No its I'll start looking for bad grounds

 

[EricM]

You could disconnect A2 from the ECU and ground it, to see if it kicks on the relay and compressor. That should force it to come on.

 

[Kevin Jones]

That worked. Is there a possible polarity issue in the config? Cannot find any ground issues. I feel like im overlooking something. In diagnostic mode, in pulse i can hear the relay clicking

 

[EricM]

So you are saying if you manually enable "High current out 2" on the diagnostic page, the AC relay kicks on? If so, then the ECU output is working.

If that's the case, then take a log, while idling, turning the AC on and off (make sure to wait more than 5 seconds in between so I can see the output come on). Then I can look at the input and output to see what it's doing.

 

[EricM]

Here's a good link that shows the details of the AC wiring: http://www.vortexbuicks-etc.com/ac_compressor_electrics.htm

 

[Kevin Jones]

Will do a log. Yes, its just that 12v positive coming out of A2 that's kicking my ass. When it gets 12v positive in at B8, I get 12v positive in A2.

Edit, actually when I turn "off" on the diagnostic the relay closes. Not "on".