34blazer

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?

*edit* or does something need to be changed in the code?

Thanks in advance!

RBob

iTrader: (1)

All '7730 ECM hardware is the same. A '7730 is a '7730. What does differ is the firmware. Such as running $88 or $8D or even $8F (among 10 others or so).

And even among the same firmware the A/C control differs.

Chill out and let us know what you are trying to do. Along with which mask is being used...

RBob.

34blazer

LOL chill mode enabled

Im trying to get the ECM to control the A/C clutch relay, and apparently there is no such logic within $8D. Still using S_AUJP. So unless my programming skills develop exponentially overnight, im not going to be able to come up with something by tomorrow. Vegas heat is beginning to fry my brain so im thinking about using the HVAC controls to trigger the relay until I can figure out what needs to be done with $8D. Unless someone wants to talk me through it???

RBob

iTrader: (1)

OK, the Corvette's used $8D in the '7727 and controlled the A/C relay via the ECM. The following pin designations are for the '7730 ECM.

Pin F3 is the relay control output. It can only supply a ground, so the other end of the relay coil goes to IGN+.

Pin D3 when grounded requests that the ECM turn on the A/C compressor (via the relay).

Pin C9 is from the A/C compressor clutch (+ voltage), and lets the ECM know when the clutch is engaged (idle & IAC control).

Pin D12 is grounded when the A/C pressure is low. When the A/C pressure increases the switch opens allowing that input to go high (internal pull up). This is the fan request input. I didn't look but there should be an option flag for that input, as to which is which to request the fan.

Can see it all here as Method 2 of A/C and Fan Control:

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

RBob.

34blazer

Freakin Awesome

Thanks Bob!

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?

Tuned Performance

iTrader: (92)

Did you try e8 ?

34blazer

the fan relay control?

34blazer

is there battery voltage present at D3 and when its grounded the ECM will activate the AC clutch relay?

the fan1 control at E8 has voltage present until fan is commanded on and voltage goes ground from the looks of it. I was thinking about splicing E8 with D3?

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

RBob

iTrader: (1)

Good to hear that you have it going. Yes to D3, there is a resistor on that input to IGN+. So it will show vehicle voltage until pulled down (grounded).

RBob.

34blazer

Thanks again Bob, AC is nice and cold!