7730 A/C clutch control

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05-12-2013
34blazer

7730 A/C clutch control

so im troubleshooting my A/C wiring on the POS fiero, ever since I swapped to the 7730 the A/C hasnt worked. today I found out that the high pressure switch is toast, ill probably bypass it. and for some reason the ECM wasnt energizing the A/C clutch relay either. according to the fiero wiring diagrams, the ECM energizes the A/C clutch relay but means of ground triggering.

the 7730 uses pin F1 to trigger the relay. One wire is 12V hot from the A/C controls and the other(to ECM) SHOULD be ground triggered. Well its not, the wire from the ECM is 12V hot as well. WTF! the wiring diagrams im using are for the TPI cars and show it as a ground trigger.

The only thing I can figure is this computer may be different since its off a 92 J body car(V6). I also tried a backup 7730 out of another J car. Both ECMs send 12V to pin F1. Im going to look around for the J body wiring diagrams to see if its different from the TPI cars.

Now heres the million dollar question, can I just reverse the polarity of the relay so that the wire that was orinally hot(HVAC controls) is now the ground? or will I burn up a foil layer(or something else) in the ECM?

Thanks in advance!
05-12-2013
34blazer

Also ,since im using $8D S_AUJP, and the wiring diagrams dont show the ECM as a trigger for the A/C clutch, does that mean something has to be changed in the code?
05-12-2013
Six_Shooter

Were you checking the voltage on the A/C pin with the relay plugged in and the A/C control set to a position that would provide the 12V to the relay?
05-12-2013
34blazer

Quote:

Originally Posted by Six_Shooter

Were you checking the voltage on the A/C pin with the relay plugged in and the A/C control set to a position that would provide the 12V to the relay?

Yes to all. With everything on and plugged in, both pins at the relay(for coil) are HOT. When I turn the HVAC controls to off, they both go cold. Same conditions when the relay is unplugged.
05-12-2013
Six_Shooter

Looking through my diagrams I see that F1 can be used for both the A/C compressor relay and shift light. It is definitely a ground trigger.
05-12-2013
Six_Shooter

Quote:

Originally Posted by 34blazer

Yes to all. With everything on and plugged in, both pins at the relay(for coil) are HOT. When I turn the HVAC controls to off, they both go cold. Same conditions when the relay is unplugged.

The wire should be dead with the relay unplugged. With it plugged in, and the ECM not triggering the relay, there will be 12V on that wire between the relay and the ECM, this is normal, since the coil in the relay allows the voltage to be seen on both sides of the coil, when connected to only one side.
05-12-2013
34blazer

Quote:

Originally Posted by Six_Shooter

The wire should be dead with the relay unplugged. With it plugged in, and the ECM not triggering the relay, there will be 12V on that wire between the relay and the ECM, this is normal, since the coil in the relay allows the voltage to be seen on both sides of the coil, when connected to only one side.

yeah nevermind, I just double checked with the relay unplugged and youre right. going to try a newer style relay to see if it triggers that.
05-12-2013
34blazer

Just tried another relay and no joy. Both ECMs must be messed up or something because I can manually trigger the relay. for $8D pin F1 is for a shift light, could that be why F1 doesnt ground the circuit?
05-12-2013
Six_Shooter

Are you meeting all parameters to allow the ECM to trigger the A/C relay?
05-12-2013
34blazer

Quote:

Originally Posted by Six_Shooter

Are you meeting all parameters to allow the ECM to trigger the A/C relay?

looking at wiring diagrams for $8D and in the hac, no A/C compressor relay controls at all. looks like a patch may be needed
05-12-2013
Six_Shooter

There should be no patch or anything of the sort needed.

What I'm asking about is are all of the parameters that would be set in the ECM being met, such as RPM, A/C request, etc, etc?
05-12-2013
RobertISaar

91 firebird 5.7:

http://i.imgur.com/IwDVFCz.png

odd.... GM chose to have compressor operation controlled by the HVAC switch along with what looks like high and low pressure switches to shut the compressor down when necessary. the ECM only tracks the status of the compressor clutch. odd that not even a relay is used, all of the current goes through the HVAC switch.

from the sounds of it, you're going to be doing some rewiring or patching SAUJP to monitor and act upon an A/C request signal.
05-12-2013
34blazer

Quote:

Originally Posted by Six_Shooter

There should be no patch or anything of the sort needed.

What I'm asking about is are all of the parameters that would be set in the ECM being met, such as RPM, A/C request, etc, etc?

Ive been looking through the definition and cannot find anything that controls the A/C clutch relay. Only items that relate to A/C are for IAC, fuel(pw?), and fan.

A/C clutch relay is controlled on pin F1 with $88 and $A1, but for $8D that pin is used for the shift light.

Now i can get the clutch to engage by grounding the circuit connected to F1.
05-12-2013
34blazer

Quote:

Originally Posted by RobertISaar

91 firebird 5.7:

http://i.imgur.com/IwDVFCz.png

odd.... GM chose to have compressor operation controlled by the HVAC switch along with what looks like high and low pressure switches to shut the compressor down when necessary. the ECM only tracks the status of the compressor clutch. odd that not even a relay is used, all of the current goes through the HVAC switch.

from the sounds of it, you're going to be doing some rewiring or patching SAUJP to monitor and act upon an A/C request signal.

I can monitor clutch operation with the adx and it does show clutch engaged when I manually trigger the relay.

other items in the datastream are: a/c req, a/c high pressure, a/c low pressure, a/c clutch indicator, A/C First Pass with HI MPH, and A/C Disabled via HI MPH
05-12-2013
Fast355

Quote:

Originally Posted by 34blazer

looking at wiring diagrams for $8D and in the hac, no A/C compressor relay controls at all. looks like a patch may be needed

No patch needed I was running dual fans and controlling my 83 G20s stock WOT compressor cutout relay with SAJUP v3 and stock AJUP. Just have to adjust the values in the constants because they defaulted disable. The $8D code also idles much better when controlling the a/c.

IIRC it was used in a Vette application. I one had a 7730 to 7727 pin chart. For all practical elecrrical purposws they are the same ecm. If anyone has that chart its pin A13 in a 7727.

Edit- I found my notes and it looks to have been on F3 maybe.
05-12-2013
Fast355

Just ran across that chart...F3 it is!!! Move your compressor control to F3 and make sure it is a N.C relay. It only grounds to disable the A/C. A13 in a 7727 and F3 in a 7730 are the same quad driver number therefore electronically the same.
05-12-2013
34blazer

Awesome and Thank You!

RBob also has the diagram(option 2)

http://www.dynamicefi.com/EBL_P4_Drawings.php
05-12-2013
Fast355

Quote:

Originally Posted by 34blazer

Awesome and Thank You!

RBob also has the diagram(option 2)

http://www.dynamicefi.com/EBL_P4_Drawings.php

No problem I hope you are able to get it up and working
05-12-2013
34blazer

No Joy

moved the relay control wire over to F3.

AC req from HVAC is at C9 thats 12V, should I put that on D3 as well?

*edit* It works now, spliced into E8 with added pin at D3
09-25-2013
JP86SS

A/C code changed.

Quote:

Originally Posted by 34blazer

No Joy

moved the relay control wire over to F3.

AC req from HVAC is at C9 thats 12V, should I put that on D3 as well?

*edit* It works now, spliced into E8 with added pin at D3

Remember in the latest S_AUJP, the clutch is not disabled at high speed as in the original code.
just don't go stomping too much with the A/C on. :)

Most of the code jumps up the RPM when A/C is turned on.
Jp