90 Miata, A/c compressor turns off and idles high when hot

[Baron]

Trying to get some help, without chasing my tail around to find the answer.

A/c blows cold, run down the highway all day without issue. On hot days (like today) when I stop in traffic or a stop light, the compressor will turn off and at the same time the idle goes up to ~1800 and bounces from there to ~2100 and back down quickly. Get back to moving again, and it calms down and the compressor kicks back on.

Fans getting weak?
Compressor crapping out?
Wiring issue?

Thanks

[jrj512]

Low freon?

[Baron]

Ive checked it. It's a 134 conversion, pressures are good, blows about 42 degrees.

[POS Racing]

Check Amp draw on the fans.

Clean out your condenser if its nasty that helped on my kids '02.

[Baron]

Check Amp draw on the fans.

Clean out your condenser if its nasty that helped on my kids '02.

Ill check them tonight, and pressure wash the condenser. I googled this problem, and wasnt seeing good solid answers, but the fans going out or not keeping up was mentioned.

[sammm]

Tired fans/motors are a known issue on these older Miata's.

[Keifersmith]

Ill check them tonight, and pressure wash the condenser.

I wouldn't pressure wash it, the little fins bend really easily. somebody just recently posted about using a can of AC condensor cleaner from home depot and just water from the end of the hose to wash it off, maybe use your thumb for just a little pressure. going to do this myself soon when I get a little spare time.

[POS Racing]

I wouldn't pressure wash it, the little fins bend really easily. somebody just recently posted about using a can of AC condensor cleaner from home depot and just water from the end of the hose to wash it off, maybe use your thumb for just a little pressure. going to do this myself soon when I get a little spare time.

Yea don't use a pressure washer the condenser may be OK with it but the radiator directly behind it is a delicate little soft aluminum flower.

I was the one on the condenser cleaner. See -> http://www.dfwmiata.com/threads/2617...ight=condenser

IIRC the Mazda specifications 5.5 to 7 amps on the fans.

[Yeller90]

I took the soft brush with my shop vac, it was amazing hearing how many little pebbles it sucked out of the condensor.

[farphle]

Not enough airflow across the condenser. I had the same issue on my '92 until I ditched my PWR radiator and went back to stock. The fans couldn't pull enough air through the condenser with the thicker radiator in the way. So, you may have weak fans or some other obstruction.

[motorollow]

My PWR radiator and Spal fans work great. My temp gauge actually drops when I turn the a/c on!

[HudsonHawk]

My PWR radiator and Spal fans work great. My temp gauge actually drops when I turn the a/c on!

Glad those are still working for you.

[Baron]

Not enough airflow across the condenser. I had the same issue on my '92 until I ditched my PWR radiator and went back to stock. The fans couldn't pull enough air through the condenser with the thicker radiator in the way. So, you may have weak fans or some other obstruction.

I was wondering if that was the case. I havent have a chance to check them, but they are a common fail item, apparently.

My PWR radiator and Spal fans work great. My temp gauge actually drops when I turn the a/c on!

And that was what I was thinking about doing, the Spal fans move quite a bit of air and are miserly on power.

Thanks for the responses gents.