bureau13

I feel like I should apologize for not having one huge HVAC/Dash and console disassembly thread, but...damn that would cover a lot of ground.

Anyway, I replaced all of the vacuum diaphragms, tested (had to replace one) solenoids, reconnected everything, started up the car to see what worked and what didn't.

AC still works, as in the compressor comes on and blows cool air, and the blower works at different speeds. I also see the lever arm from the settings motor move when I move the temperature slider.

What doesn't seem to work, is pretty much everything else. I never see the comb flap move, I never see the recirc flap move, I never get air to route through the defroster or the lower vents, etc. Also, despite that movement of the settings motor arm, setting the temp to hot doesn't seem to make it so...I still get cool air.

This tells me that whatever is supposed to trigger the solenoids to do their thing is not doing so (odd however that I never get hot air...I thought that was supposed to default to heat?) I am quite sure that my control unit has some issues. Most of the times, the blower shuts off for any air routing selection other than middle vent or defrost. Sometimes I can jiggle the switch in other positions and the blower will turn back on, but it's not reliable, so I'm basically debugging the center and defrost positions right now. In any case, I THINK that this is pointing to a settings motor issue for the (lack of) heat, failure to route to defrost vents and failure to activate center and recirc vents when in the two functional settings of the controller.

The first test of the settings motor in the WSM say to remove inside plug and test voltage between terminal 3 and 11. I get 0V. So right off the bat things are not good.

Now, a question: I've been assuming I should test this at terminals 3 and 11 on the settings motor, NOT on the connector. If I'm wrong, someone please yell at me.

The other thing I just realized was that I've broken the sensor chain, because the cabin air sensor is not connected. Damn, I forgot about that. So that may be screwing with the temp calculations...would it cause all of this other stuff? I thought a broken sensor chain caused all-or-nothing heating/cooling. I've (sort of) got the all-or-nothing cooling, but the temp mix lever arm is still activating, just nothing is controlling the solenoids.

I'm half tempted to say screw it, prop open the recirc valve and put it all back together, because South Florida does not require subtle changes in temperature right now, it just requires blasts of cold air...but dammit, I spent time and money to fix this stuff and I feel it should work properly.

Sorry I've written another book here, but any insight into this stuff is appreciated...

Alan

Sounds like the motor works. I'd be investigating the water valve - seems it never turns on.

Yes it sounds like you have head unit issues - the flap position should not modulate the blower, any position but off should enable the blower. There is a switch track for this - it must have a bad wiper try cleaning that up.

Alan

bureau13

The water valve is new...just installed it. When I tested it prior to install with a vacuum pump, it seemed to work fine.

My fear (before I put the dash and center console back together) is that the settings motor is also bad. But you're right, it is moving the lever properly. My impression from reading things is that the settings motor also takes signals from the controller and sends them to the solenoids. Is this not true? If those signals come straight from the controller then that's definitely where the issues lie...

Alan

So does the water valve actually operate correctly from the vacuum actuator (by default it should be open without vacuum), however it is possible it is always closed with the engine running... Worth investigating

Alan

Kevin in Atlanta

The vacuum manifold gets its signal to pull vacuum to the water valve from the setting motor. The setting motor may appear to be working and yet no signal. BTDT

bureau13

Before I installed iiithe water valve, it worked properly when I pulled a vacuum on it. FWIW, this was happening with the old one too (the lack of heat) although in that case, I was getting a vacuum leak and a small coolant leak. I wonder if a PO may have given it a constant vacuum source? Yet I know I pulled a vacuum from inside the cabin with the new valve and the leak had stopped...

Regarding the settings motor, does it also tell the other solenoids what to do? I'm becoming highly suspicious of this thing. I can replace it with the dash and center console in place right? Just go up and under? It almost seems like none of my solenoids are getting activated..

bureau13

Btw, anyone know what the connection on the back of the HVAC controller is supposed to be for? I have two connectors that attach to the left side of the controller box, a sort of plug, and then an edge connector, but the back of the unit has another edge connector type thing, but I have nothing attached to it.

The Forgotten On

The right side (passenger side) of the control head should have another plug into it.

Check to see if someone stuffed it somewhere in your center console.

bureau13

Damn...I wonder what I'm missing because of that? If that's what tells the settings motor to do it's thing with the solenoids, that would make perfect sense!

GregBBRD

^^^^^^Not in 1986.^^^^^^

As the setting motor moves through its range, the heater valve gets vacuum and various other solenoids turn on and off.

The lever than moves on the setting motor opens the door that isolates the heater core. Although the heater control valve shuts, there is always hot water in the heater core....from the water flowing the other direction. So, even if the heater valve is shut, there will be hot air coming off of the heater core, when the setting motor opens that door. The fact you have zero heat makes me think that the door is not opening.

bureau13

Damn...missing plug sounded like an easy solution!

I've watched the lever arm from the setting motor move but I never actually verified that it was moving the flaps. That's a good point, and would explain what I'm seeing with the heat.

I seemed to be getting "battery voltage" (a bit low actually, around 10V, although I was using a weak 9V battery to test the solenoids, and it was enough) at the various pins on setting motor connector 1, as described in the WSM, so I'm still not really sure why the solenoids aren't firing (I am making a possibly incorrect assumption that those pins are supposed to trigger the solenoids) unless the solenoids are actually activated by grounding one side, as opposed to applying "12V" to the other side.

In any case, it's probably a bit of a lost cause trying to diagnose this stuff when the controller is known to be flaky and the sensor chain is not complete. I need to take care of those pieces first, I guess...

dlagerstrom

Yes, step one should be to make sure the sensor chain is complete and you have 1000 ohms difference from cold to hot on the temp slider. The 'automatic' temp control is actually quite amazing for it's age. Everything is based on the cumulative resistance of the temp sensors and the potentiometer attached to the temp slider.

Good luck.

GregBBRD

Always best to fix what you know is wrong, before doing anything else.

The Forgotten On

Oops Thanks for the correction. Now I know a bit more

bureau13

Well, a bit of good news...I discovered that I had somehow knocked the HVAC vacuum supply line out of the little connector in the engine bay. No wonder none of the flaps were working. I reconnected it, and while I didn't do an exhaustive test, I confirmed that center vent selected and max cold, the comb flap and recirc flaps work as expected.

This doesn't explain the heater issue, which I haven't chased down but I suspect is as Greg hypothesized earlier. I'll get that working at some point, but it's not critical at the moment, as the last thing I want 300 days out of the year down here is any heat at all lol...