zekgb

After spending a couple of days resolving some vacuum related HVAC weirdness, my AC was working quite well for a few weeks until a couple of days ago when simultaneous to crossing a set of railroad tracks I was serenaded by a cacophony of clicking behind the center console. The clicking would speed up and slow down somewhat randomly but would always speed up when I hit a pot hole or would otherwise jar the car. Turning the AC off would stop the clicking. About ten minutes later the AC started blowing warm and I could tell from the dash voltometer that the AC clutch had disengaged. I shut off the AC, and five minutes later started it again and it worked, but the clicking returned in five minutes or so and the clutch disengaged again 10 minutes later.

Back in the garage the AC worked fine, but as soon as I took it out on the road the problem returned. I can get the clicking to start by banging on the center console while the car is stationary. I've read about the head unit relay issue and I'm prepared to dive in on that one, but I'm thinking that there is something else going on here (maybe some kind of ground issue?) Has anyone heard of/seen anything similar?

dr bob

Pull the left side carpet cover from the console. Reach up to feel the connector at the rear of the HVAC controller, forward (towards front of car, front is front...) of that controller, and reseat the connector there. It's a card-edge connector that mates with the PC board that's the middle of the controller. There are no clips or retainers for that connector, making it a candidate for a bump/jar/disconnect.

The AC switch in my S4 is in the skinny panel below the AC control head. There's another unsecured connector on the back of that panel, just forward (in the car...) of the AC pushbutton. Mine likes to come a little loose when I have the radio head unit out. You may be able to reach up betwen the radio and the AC controller to reseat that connector. Otherwise the radio is the easiest thing to take out to access the little connector.

Then there's the relay fix. If you pull the head unit, you might as well just do the fix. If you don't need it already, you will soon.

zekgb

OK, checked the connections and the AC button connection was barely in place, snapped it back into place and voila, no clicking AND a working AC button light! Unfortunately in the process I discovered that my HVAC vacuum solenoid manifold looks like this:



As good as it is, this car makes me feel like Roseanna Roseanna Danna...

dr bob

A mr.howard fader of fort lee new jersey writes in:

Dear Rosanne Rosanadana:

You can buy that little manifold piece, or make a temporary substitute piece with some vacuum hose and a couple plastic X pieces you can find at the your POLAPS in the help section.

soontobered84

Old thread resurrection. My AC head unit is doing this exact thing. The strange thing is: the AC head unit that is in there is a previously rebuilt one from 928 Intl. I replaced THAT head unit with a Doc Mirror rebuilt one (with the external relay dangling) and it does exactly the same thing. I put the orginal rebuilt head unit back in and have been driving it, but noticed yesterday that as the head unit clicks, my left fog light also goes out and comes back on in some correlation to the clicks.

Any ideas?

Alan

Find the X relay and swap it (not the Relay in position X) - the X supply repeating relay.

This controls HVAC and foglights

Alan

soontobered84

Thanks for responding Alan! I was hoping someone with a lot more electron knowledge such as you would chime in. I should be able to find the correct relay to replace, but I realized too late that I didn't give the model year of the car (the '89) I am having issue with.

Just for my general knowledge, what is "X supply repeating relay"? What does that mean?

Alan

There is an X bus ( a power supply line) from the ignition switch - its the accessory feed - on with the key in positions 2 & 3 (of 1-4) - e.g. on before ignition & off during starting.

There is a relay that just repeats that same function to provide a lower loading to the ignition switch.

It has various names over the years but the function is the same. On your year it is just called "Relay X" and is in position IV.

Alan

Tony

On this topic is there a good write up on disassembly of the control head?

soontobered84

Tony,
Dwayne has a good write-up, of course, but what are you trying to accomplish? Replace the relay, change the sliders, add LED illumination, remove the fiber optics and put individual LEDs in the sliders, or add LED illumination to the blower motor switch?

Alan,
Thanks for the explanation of the X relay. I had always seen that but had no idea what it was.
I swapped some relays around, but I need some new relays, methinks.

Tony

found what i needed. Just wanted the bulb out...but while Im at it now, Im going to replace my relay.