MS3x A/C Jumper - Please verify
 

Okay - so there's the A/C Faq I've read multiple times and tried to reconstruct the broken images with the words. I *think* I've done everything right - but I'm still not getting A/C. I also *think* it's not on the megasquirt side, but I just want someone to verify this is correct -

94, MS3x, Fans wired for dual control -

1Q == 1J =-|<|-= 1L == 2S

1Q and 1J are jumperd together, 1L and 2S are jumpered together, there is a diode that connects 1Q+1J and 1L+2S together with the band pointing at 1Q+1J side.

Correct?

2S - condenser fan
1L - main fan
1J - a/c switch relay
1Q - thermoswitch / pressure switch

No one with a MS3 or MS3x should be following ancient write-ups designed as a band-aid solution for ancient ECUs that had not the ability to control a/c properly.

With that said, no one with an ms3x should be following any ms1 or ms2 write-ups at all.

Use the documentation on Megasquirt MSEXTRA Manual Index or Frank's MS3 writeup here: 90-97 MS3 with MS3X | My Westfield MX5 90-97 MS3 with MS3X |

your MS3x has the ability to control and handle a/c functions quite well.

Here's what you need to do for your 1994 on megasquirt 3 to control the air conditioning function:

First you got the pinout incorrect.

1Q - A/C Switch
1J - A/C Relay
2S - Condenser Fan
1L - Main Fan

Wiring:

Connect 1Q to ms3x-28. This will bring the a/c switch into the "table-switching" input.
Connect 1J to ms3x-1. This output will run from INJ-G to the a/c relay.
Connect 2S to ms3x-20. This output will from INJ-H to the a/c fan.
Connect 1L to ms3x-4. This output will run from INJ-F to the main fan.

So basically what we have done is connected the a/c switch into one of the 4 inputs, and the fans and relay on 3 separate individually controlled outputs.

now here's what you'll do in software:

To control the a/c function set it up like this --

https://www.miataturbo.net/attachmen...1&d=1341670622

As you can see the input is set to "tableswitch" and the output is set to the INJ output we wired to the a/c relay.

To control the a/c fan --

https://www.miataturbo.net/attachmen...1&d=1341670285

We set the fan control function to run the a/c fan. You'll notice it's setup to run with a/c activation and the temperature set to activate it higher than normal.

To control the main fan --

https://www.miataturbo.net/attachmen...1&d=1341670285

We use the generic outputs to control the main fan with a simple temperature trigger. Notice it turns on 10° before the a/c fan would otherwise.

BTW, if you're fans are wired together, please undo it. it's stupid.

Thanks so much Brain - that's clearly the right way to do it. I think I finally managed to trace my original problem down to the A/C switch miswire (NB -> NA dash + heater swap).