intermittent stall with ac compressor cycling on my miata

[nismoautoxr]

Hi guys...I am experiencing a very intermittent anomaly when running the ac on my miata. I'm using the MS3 to cycle the compressor . Sometimes if its idling and the compressor cycles off it will stall as if you cut off the key or it lost synch. Other times if you are headed down the road at speed with steady throttle it will hiccup like power was interrupted for a split second . Only when operating the ac. I was finally able to catch it on a log today while idling. Everything but the cts,mat,and tps goes haywire when the near stall happens . Here is the log . Anybody seen this?

[muythaibxr]

How are your grounds/power for the AC and MS wired?

[arran]

Looked at the log. Status 6 shows the AC coming on, and is immediately accompanied by the Idle valve duty reducing from 54% down to 40%. Don't know your setup, but in mine it goes the other way

[nismoautoxr]

Here is my tune guys. Ken...the grounds are as prescribed per the assembly manual as far as I know . This install is using a BoB conector per a factory stock 1997 mazda miata efi harness. I had to use a relay in the AC circuit to make it work. I need to dig up the circuit because I did make a thread when I was building this circuit. This is a very intermittent issue.... maybe every 20 ac clutch cycles. The main thing here is that it will almost kill the motor going down the highway at 70 mph with a steady throttle. That is not what is demonstrated here in the log but it does. That is why I have dismissed a idle air control problem.

[Matt Cramer]

How precisely is the A/C input wired up?

[nismoautoxr]

How precisely is the A/C input wired up?

http://www.msextra.com/forums/viewtopic ... 32&t=61883

This is how i built the circuit on the ms3 board. I wired the bob exactly as diyat did it on their diypnp guide....however, i had to use a micro relay switched to ground because my evaporator temp.switch for some reason does not switch a strong enough ground on its own. It worked perfectly fine on the oe ecu but not with the circuit on the ms3. Had to use the relay to make it work.

[nismoautoxr]

Any thoughts Matt Cramer? This car is wired exactly as the diypnp guide said but when i tried to use the ac it would almost immediately stall. When i added the relay the problem went away for the most part but it still occasionally does it which is why I started this thread.

I used the top circuit http://www.msextra.com/doc/pdf/html/MS3baseV30_Hardware

I bought a diy bob so i could just do a pnp to the 97 miata harness. I wired 1k to the input to the ground switch circuit above. This didnt work good at all untill i added the relay. If i ground this circuit then it obviously works fine but that doesnt fix the fact that the compressor needs to be cycled to keep the evaporator from freezing.

[Matt Cramer]

You can use an analog input and a loop condition. Tell it the A/C is on when below 2.5 volts.

[nismoautoxr]

You can use an analog input and a loop condition. Tell it the A/C is on when below 2.5 volts.

Not completely sure i follow Matt. I gotta go and look in the tune and see what pin im using. Its been a while .

[Matt Cramer]

The Mazda A/C input is a bit weird. It doesn't always go to 0 volts when the A/C is on, depending on how you have the blower fan set.

[nismoautoxr]

The Mazda A/C input is a bit weird. It doesn't always go to 0 volts when the A/C is on, depending on how you have the blower fan set.

Yes im noticing that too. So its not the switch itself but rather the input to the switch that is the problem then. Makes sense from what im seeing .