I am aware that this IS NOT the "Megasquirt Section". Please read the entire post before lighting me up.

I`m working on a Megasquirt for my `86 GXL. I would like to make it "Plug and Play", my question is this. Will the A/C or the Cruise Control be affected if I remove the factory ECU completely. I would like to plug the Megasquirt into the factory harness (via a custom adapter) but since my A/C and cruise both work I don`t want to disable them. Do I need the ECU for these two to function correctly?

TIA

 

yes, he factory rouets the A/C pressure sensor through the ECU to run the compresor. you should be able to jumper it

 

Thanks Icemark, I thought you would know if anyone would.

Any idea what I need to jumper to keep the A/C going?
And what about the cruise?.........or does that have its own "computer"?

 

The cruise control is completely seperate from the EFI system, so don't worry about it.

The ECU basically grants or denies permission for the A/C to run by intercepting the A/C relay circuit. I'm not entirely sure under what conditions the S4 ECU turns the A/C off (the S5's is cut over half throttle) but I know on most cars these days the ECU cuts the A/C over a certain rpm (to minimise compressor wear and engine load) and if the coolant temp gets too high (to combat overheating). The S5 FSM's Relationship Chart lists the CAS as an input related to the A/C relay, so my guess is it's cut over a certain rpm.

The wires in question go to ECU pins 1E and 1F and are part of the front harness. You'll need to cut them from the plug and join them together. The A/C system will now run independant of the EFI system.

 

No thats what I needed to know. Also based on that info I should be able to use a custom circuit on the Megasquirt, or a daughter card for it, to cut the A/c above a certian RPM just as the ECU does.
Thanks for the help.