A/C On Idle goes crazy
 

While driving the A/C works fine but when I stop sometimes the idle jumps to 1800-2000 and then down to 900 then back up, I just keeps jumping around. Sometimes its fine and stays normal. Any Ideas?

Yeah. Tune your idle

I assumed that but I only have one Idle speed target map, I don't see anything that shows a modifier for A/C on or off. It's almost like it's jumping between open and closed loop. Is there another area that it could be affecting making it switch to open loop?

It's your PWM1 map.

Swap to NA8 alternator and don't look back.

Which hydra do you have?

Have you logged the issue?

Can you post said log.

Whats turning on when the a/c jumps your fan or a/c clutch?

i have the same issue. getting a tune tomorrow, hope it goes away

I'm on 2.17 and I have the same thing....sometimes a good smooth idle...sometimes is oscillates and can even stall. Interesting on the NA8 alternator.....any wiring involved with plopping that sucker in? Why does it work? Any tuning needed to go with it?

I believe you change/remove one wire from Hydra, and then turn off alternator control in Hydra.

Done.

I think Jeremy has the write-up on FM's site. It's been posted here before, i'll find it. :)



[edit]

Got it. It was in one of your past threads. :P

https://www.miataturbo.net/hydra-58/...72/#post890999


I should clarify my gross blanket statement i made earlier. I've seen reports that alternator control finally actually works well in 2.7, so if you're on a newer Hydra, give tuning that PWM map a shot. If you're on an older Hydra, up to you. I'm on 2.5, and we're going to give tuning it one more shot, nobody has managed to get it right so far, though. If it doesn't work this time, then i have an NA8 alternator ready to go.

Also: it could very well be something else. I know my ISC settings are garbage which isn't exactly helping anything (i experience the same issues as OP with a/c on), but i also know that some (if not all) of my idling issues are voltage related, the voltage is all over the place. (Radio cuts out when putting windows up from time to time, idle fucks up massively when cooling fan kicks on, etc etc etc)

Yeah, I never got around to that...school and work killing my time. I've been more focused on the cut-out problem and may eventually try the NA8 alt. replacement. So many other little things I've been working on as well :/

2.1 & 2.5 idle control left a lot to be desired. 2.6 was O.K., and 2.7 is actually pretty darn good. A/C off I'd call it dialed. The A/C on control isn't fully OEM, but it's totally acceptable / no worries status, and you have lots of tuning variables dedicated to it. FWIW idle control is generally one of the most difficult things to set up in a standalone.

2.7 alternator control is great, way better than before considering you also have control over the target. That said, I can email the 94-alt swap instructions to anyone who needs them. I would still do this in a race car, KISS.