TheClairvoyant

Does anyone know if the solenoids for the HVAC system can function sometimes, not function at other times?

My recirc flap was letting outside air in when using the AC. Felt the warm air from outside when using the AC.

I was able to feel the flap when sticking my hand under the passenger footwell when the AC was on. Prodded it with a screwdriver to see if it was just stuck, but that wasn't the case.

I opened things up to access the solenoids and vacuum manifold for the system to check everything with a Mighty Vac. All the actuators are holding vacuum (including the one for the recirc flap - opening and closing as should and holding vacuum) and all the solenoids were working fine when testing individually.

After checking everything, I started the car and tested the system againg. Everything is now functioning as it should, including the recirc flap - it is now in the proper position when the AC is on. Also confirmed the heater control valve is working.

Is it possible for a solenoid to start going bad and getting flaky, or could there be another reason the recirc flap wasn't open/closing properly, but is now?

The Forgotten On

My issue was a 6 pin connector that had some burning on the black power wire and an intermittent ground wire connection. I replaced those two connects with 2 spade connectors and haven't had a problem since.

The solenoids would only work if I shook the connector enough to get it into the right position, which lead to intermittent faults fixed by the solution above.

It's easy and worth a shot to check out.

TheClairvoyant

Thanks. I'll check that out .

SeanR

A few times I've found that the rheostat in the head unit stops doing what it does so the temp control failure is there causing the mixing motor and solenoids to not do what they should. I actually pulled mine yesterday to pour some Deoxit (thanks Stan) to see if I can make it work. It's happened a few times in the past on cars and tossing a new head unit has fixed it.

The solenoids can go bad, so finding the one that doesn't work right can be fun.

Alan

If you lose vacuum all or various of the active actuators will drop out temporarily until you can recover enough vacuum to restore it (lots of vacuum at idle/low throttle - but almost no vacuum at large throttle openings/WOT). Your vacuum actuators rely on no leaks to work continuously - but they will work most of the time when there is strong vacuum that can overpower a small leak... until you stay at ~WOT for a while - sustained acceleration, climbing a hill etc...

Alan