A/C Troubleshooting (It's getting HOT out!)

[mark10t]

The A/C in my '94 Touring Wagon is operating intermittently. A tech I know said he saw a similar problem with a thermostat that snakes into the evaporator(?), so that may be it, but I'd like to research the system. I already know there are no leaks and I have a proper working freon system- it is some kind of electrical snafu.

I've set up a jury-rig to 'force' the compressor on as an interim measure, but I'd like to actually try to fix the problem.

Does anyone have the A/C section out of the manual and/or the elec. schematics that cover the HVAC for the car in .PDF format that I can use? Or has someone scanned in any sections of the manual and have them online?

I'm melting!

Help if you can.

-Mark

[mark10t]

Boy am I glad I had the A/C overridden 'ON' last nite- a real cooker.

Any help yet?

-Mark

[Legacy777]

what exactly is it doing? what are the symptoms?

There is a temp sensor in the evap box...

[mark10t]

It intermittently turns on oand off. Normally, Subaru compressors are 'on' most all the time with 'off' periods only to defrost, etc. When the compressor does choose to come 'on', the fans start, too.

A tech I knew said their is a sensor with a long tube(?) that snakes into the evaporator that he experienced a similar problem with another customer's car.

I'm looking for info on locations, connectors, etc for that sensor and/or all the A/C related devices. If I don't actually replace the sensor, there may be an easy way of 'cheating' it.

-Mark

[Legacy777]

Have you checked the pressures on the a/c system....just to check? Also....what does it look like in the site glass?

If you remove the glove box and then resistor pack from the evaporator box You should be able to see the evap core, and feel if it's cold or not. You'll see where the temp probe inserts into the evap box.

[mark10t]

Already checked out the pressures- everything's OK. If you jumper the compressor clutch 'ON', the A/C blows nice and cold. The problem is some kind of interlock/thermostat/switch/ etc. that is intermittently turning 'OFF' when it should be 'ON'. Something is marginally failed.

-Mark

[Flip_x]

mines been doing that sometimes the ac clutch doesnt turn on so i just press ac off ac off ac off till it starts but since it turns on now but sometimes it doesnt

[Legacy777]

wonder if it's a pressure switch.....could be that....could be the temperature switch....I'll see if I can find any diagnostic/checks when i get home.

Remind me if I forget.

[Legacy777]

here's the only info I found

The A/C relay, main fan relay, sub-fan relay, & fan control relay in the engine bay fuse box should be around 100 ohms on pin 3 & 4. and infinite resistance between pins 1 & 2.

For the A/C cut relay found on top of the evap box should be around 120 ohms between pins 3 & 4, and infinite resistance between pins 1 & 2.

Unfortunately I found no info on the thermister switch.

[IronMonkeyL255]

Could it just be another failing HVAC unit?

That's what's happening in mine, and I know it's the HVAC unit.

It works when it's a bit cooler, but once it gets hot (and you need the a/c) it won't work. Then I smack the dash above the unit and it will start up.