ratoflic

Hi,

Me again. I have another question for experienced people who do allot of LSX Swap.

I buy a kind of standalone AC controller from vintage air in my 74 nova. On the front, I put a R4 AC compressor with LS bracket stuff.

My AC is a 2 wire. For what I know, when the AC is on..the RPM Drop little bit.....and probably run too slow if the ECU doesn't recognize if the AC is on...to make the engine to run little bit higher to compensate the AC running ECU need to know that this one running.

My AC is a kind of standalone stuff....How Am I able to give to ECU a signal that telling him the AC running and climb up little bit the RPM ?

Thanks for your input.

2008 5.3 Liter E38 ECU.
Stephane

PS (Sorry for my English, I'm French Canadian and do my best to speak in English)

imma_stocker

iTrader: (19)

Here's the E38 PCM pin diagram.

http://lt1swap.com/E38%20ECM%20Connector%20Pinouts.htm

Pay attention to pins 12, 13, and 63

ratoflic

Was looking the 3 pin out you telling about.....CAN you telling me wich one i need to applied the positive wire to telling my ecu that the A/C is
engaged !!!!

brawls43

From what I've read about E38's is that you can only tell it the AC is on over CAN. There is no AC request signal that's 12v like in the older ecm's. The pins mentioned in the above link are pressure sensors and the relay control.

I'm surprised to hear your rpm's drop, from what I read, most people say the drive by wire throttle will compensate for the AC load, to try to keep idle the same. I'm just finishing up wiring my E38 L76 engine and stand alone AC system, so I'll find out shortly.

imma_stocker

iTrader: (19)

I don't think the PCM adjusts idle for A/C.... it should disengage the compressor clutch at X% throttle, disengage at Y psi charge pressure, reengage at Z psi charge pressure.

Standalone A/C (I think) means it won't connect to the PCM.

garys 68

iTrader: (1)

Don't worry about AC request to ecu.
I'm running 2 standalones (Vintage & Classic) with no issues.
I would recommend the trinary switch for fan control.

ratoflic

OK folks...thank for all your help. My A/C is not hooked up right now. I tried to find problem before they arrived

Gary,

What do you mean by Trinary switch for fan control ?

I have a Classic Auto Air setup with the R4 compressor !

Stephane

hookemdevils22

iTrader: (12)

The trinary switch threads into the receiver/dryer, and turns on the electric fan with the AC via a ground signal to the fan relay. You likely received at least a binary switch with your kit - it's easy to tell which, as a binary has 2 wires and a trinary has 4.


Switch threaded into the top of the receiver/dryer




Trinary switch wiring