AC Problems, can the ECU mess it up?

[RatedR]

I just had my 1991 240sx FB 5-speed serviced for AC repairs and recharge. I got it back and it ran great, then out of nowhere, the damn thing shut down again. I know this because instead of the idle goin up to around 1400, it drops to 600 rpm. I took it back and the mechanic took almost all day and said it was my computer (which would be the ECU, its the only computer on the damn car!). He said that the switch wasnt sending a good signal to the ECU and that he had to resolder a part. He also said, if it fails again, to bring it back to him. I was just curious to see if this guy knows his stuff and if I can just swap out the ECU for another....any ideas? Basically here's my 2 questions:

1)Will the ECU contribute to AC failure due to poor signal given by the circuit?

2)What year 240s can I interchange the ECUs with?

THANKS!

-R

[RatedR]

C'mon fellas, Nistech? Aries? Exar? Orion? Who else? Sorry if I forget any of you big names/mods...just really looking for an answer....and a bump.

[12er]

wouldn't know #1, got no a/c; for #2, look on the lid of your ECU, there's an ECU model number and version number.. then go look for another ECU of the same model and version #s...

[RatedR]

thanks anyway 12, after talking to my friend, who's a Nissan mechanic at the dealership, he says the ECU doesnt control the AC. He says it might be the climate control unit, any thoughts on this?

[12er]

jumpy and/or poor idle... might want to check the AAC valve and related components....

[RatedR]

Idle isnt bumpy, just drops when I put the AC on.....I took out the AIV valve, not sure if thats the same as the AAC....

[12er]

AIV: Air injection Valve, this is an emission item.AAC: Auxilary Air control, this is on the intake plenum, it controls idle.

[RatedR]

ohh, my idle's set properly....thanks though

[SuperStyro]

Yes, your computer does control your A/C clutch on the ground side. This is why. When you turn your A/C on the computer gets the A/C singnal to inguage the clutch and raises the idle to compensate. Plus when you put your foot to the floor and the computer sees WOT, the A/C clutch is turned of.

So for some reason your computer is not seeing the A/C clutch command. It could be your computer directly but can also be the wiring to the computer.

My 2 cents

Styro

[RatedR]

thanks styro, after talking with my friend, he says the same thing. The ECU shuts off the AC when you're going up hill or like what Styro said. I had the ECU resoldered for $50 (I could've done it....but what the hell, there's a warranty!) Now its running fine!Thanks all!

-R

[SuperStyro]

Awsome!

Styro

[im two techno]

I don’t know about a 93 but 95's and newer the ECU controls the ground of the compressor.