Two AC Intermittent - One Fixed

[rjundi]

So this week both my 2005 Subaru Legacy GT(151,000 miles) and my 2007 Acura MDX had intermittent AC. My MDX I lucked out with finding a TSB mentioning a bad AC clutch relay and even better finding the defective old relay only to be $6(USA part) vs $30(Vietnam) for revised larger part. Honda dealer parts guy said go for the cheaper after consulting with shop guys. It WORKED for $6!

That being said our 2005 Legacy GT either blows freezing cold/works fine or nothing. It does have Automatic Climate control like my MDX and never had any service work.

I see mentions of relays here and there about SUbaru but not like the Honda/Acura where it was an easy fix and dealer well aware. I imagine it is electrical in nature. Should I blindly replace the same part or are there many more electrical parts to look into?

 

[JHZR2]

I hate auto climate control personally, as it is a huge liability to me, IMO. The circuit boards can get bad traces themselves, and then not work properly. We see this after 150k generally, though the cars that I have with ACC are older... But that means better solder...

Freezing or nothing sounds to me like it is undercharged, the evaporator is freezing up and kicking the compressor off. Sublimation of ice doesn't cool as well as two-phase refrigerant.

Did you get operating pressures on either?

 

[rjundi]

I do not have the gauges etc for operating pressures. So unfortunately I will have to bring it to mechanic for that.

Electrically are there places on web to diagnose it or hints? It is definitely intermittent, eg left house AC not working(car last used 1 hr before). Turned off climate control(hot air is not fun). Turned it on 5 minutes latter in drive and it worked perfectly moderating the temperature etc.

The ACC does not scare me much on these cars. It is not known to be a common issue in either vehicle.

 

[Colt45ws]

Even manual climate control is so electronic anymore, the point is moot.

Can you run the control through its operating range and see if its operating the vents and stuff. Like on my Ford the minimum and maximum temperatures are essentially 'full cold/hot' and it does not regulate.
When its not working, can you see if the compressor is running? Is the evaporator outlet getting cold?

 

[440Magnum]

Originally Posted By: Colt45ws
Even manual climate control is so electronic anymore, the point is moot.


+1 If you worry about electronic glitches in the auto climate control, then you should worry about the engine controller, body controller, traction control, stability control, etc. etc.

I also wish we were still allowed to buy a good, uncomplicated, electrically and mechanically simple car. But since ABS and stability control (among other things) are now mandated, the point really is moot. But honestly, old manual climate control with a maze of vacuum tubing and vacuum servos was no cakewalk to service, either.

FWIW, my first vehicle with auto climate control was a 1993 Chrysler product, and I have to say the climate control on it was faultless for the whole 200k miles we owned the car. Of all the systems I've driven since, that one actually "chose" the air flow, vent, and fan speed settings I'd pick myself more often than any of the others until my current Challenger. That early system had a diagnostic mode you could get at by pressing and holding 3 of the option buttons simultaneously- it would exercise every servo through its whole range (and re-calibrate while it was at it), run the temp blend through the whole range (and re-calibrate). A few times when the climate control started acting a little different, running that cycle fixed it right up. Maybe your Subaru has a similar option, and would re-calibrate the temp/blend system. Just a thought...

 

[SwampSurvivor]

Originally Posted By: 440Magnum


+1 If you worry about electronic glitches in the auto climate control, then you should worry about the engine controller, body controller, traction control, stability control, etc. etc.


I do ...

My jeep has vacuum actuated climate control. After it sits all winter ... it spends about a month stuck on defrost.

 

[Fleetmon]

You may have a balky LP switch....costs about $14. However, as JHZR2 states, maybe the system is low and freezing up which would cause the LP switch to open.

You need to verify whether or not the compressor is running when it's not working.