HVAC switch, modulator control, purge solenoid, and vacuum lines

[daeron]

Back story: just after I got the car I broke a hose barb off of my purge solenoid. Not having a clue what it was at the time, I simply JB welded the hose and barb back into the body of the valve, and let it be. Wise.

 

A few months back, while in the junkyard, I snagged a spare purge solenoid. When I installed it on the car, I thought, "Gee, that has needed doing for a while, now, hasn't it Shawn?" and was pleased with myself. Unwise.

 

Dating from then, my cruise control has not worked (properly,) My transmission has shifted horribly, up and down, and my AC switch no longer appears to work right.

 

The data:

 

AC Switch functions, minimally. I can hear the vacuum sound when it gets switched with the vehicle on; when I push the defrost button and have the selector to heat it is definitely routing air thru a hot heater core and onto my windshield... but there is no fan! Yes, the fuse is good, yes, I try at all speeds... something is wrong. The AC Compressor clutch does NOT engage. The AC had been getting sort of difficult to turn on* for a few weeks before it all went away, but the switch has been physically broken since I got the car; the little ears for the mounting screws are broken off and it sits, sort of recessed in its hole, and ive always had to mash the buttons hard to get them to engage. The AC switch MAY have some electrical malfunction in it? but I have no clue how to test it. I DO have a spare, but I haven't wanted to take the plunge into my dashboard without knowing that I had no vacuum problems.

 

*by difficult to turn on, I mean that I had to smash the button a couple times, and sometimes could NOT succeed in turning it on.

 

 

Cruise control, factory flavor(GL-10 baby!)

 

Turn it on, light goes on. hit "Set" and it fails to keep throttle... BUT it TRIES. Its almost like the little vacuum motor that operates the throttle under cruise is anemic.

 

 

 

Transmission

Always had the "sticky shift into second when its cold" thing but never too awful; worst case, i push down into 2nd to shift it into 2nd, then into D and i was good to go from there. Once I forced the first shift into second, the car shifted perfectly normally. Now.... ye gods, I can't depend on being in first when I stop at a stop sign! MOST of the time it downshifts all the way... but the fact is, I have taken to shifting manually ANY time it "counts" just to be safe.

 

 

 

The Rest:

 

NO Check Engine light. Haven't run a D-check yet. I tried bypassing the Purge solenoid just now by connecting the manifold vacuum supply directly to the cruise control unit, AC/cabin vacuum line, and trans line. I have tried something like this before, and judging from the behavior of the AC it did nothing. I didn't test drive it because it started raining, but I'm 99% positive I did the exact same thing right after I installed the new valve and the test drive didn't show me any change.

 

The governor gear is not applecored, the modulator is smooth as silk and looks great. The car idles like a CHAMP and I HIGHLY doubt I have any vacuum leaks... I would say I am 100% on the vacuum leaks, but I go by the adage "wise men hesitate, only fools are certain."

 

 

 

So.... What electrical switching does the AC switch do? I can cope without cruise, and shifting manually isnt THAT bad.. but in 90 degree weather, with 90% humidity, and 0.9mph wind, 95% of the summer.... AND a stack of pizzas in the backseat, I NEED MY AC as anemic as it may be. I am NOT addicted to automotive air conditioning by any means; the soob is the first car I've had with functioning AC.. but I just can't cope with the heat coming from within the cabin as well as without.

 

 

So... any thoughts?

[beataru]

and you dont have a vacuum leak? oh and Bump... Im curious too.

[4WDFrenzy]

It might be the relay for the fan, which is under the driver's side dash. Remove the big panel. It(the relay) should look something like this.

 

http://www.autozone.com/selectedZip,96367/initialAction,partProductDetail/initialpartType,01321/initialR,APP1127883/initialvehicleId,1083603/shopping/selectZip.htm

 

Incidentally, you should be able to find this at your local Autozone as well. You may have to get under there with a multimeter and check for power at the connections(including at the plug for the blower). I hope this helps.

 

Patrick

[Gloyale]

you're losing Vaccum somewhere.

 

Have you tested the Check valve and the resevior.

 

You must have the cruise setup that uses engine vaccum not an electric vac pump?? But you have a GL-10, should be the "factory" set-up that uses the electric pump?? Hmmm...

 

Have you checked the relay for the blower motor?

[GeneralDisorder]

Sounds like the HVAC switch panel is hosed. It may be the source of your leak, and it's obviously difficult to operate. I say replace the obviously broken switch cluster first - then look for other potential leaks. Once you remove the surround, the HVAC control cluster comes out easily as I recall from my last heater core swap - just some electrical connectors, some control cable's, and vacuum hoses. Shouldn't take more than 30 minutes or so being you have a replacement on hand.

 

You may indeed have a vacuum reservior leak, but if the HVAC panel is using all the vacuum because of a leak there might not be enough left to operate the CC.

 

GD

[daeron]

Okay, so I am getting "check the fan relay," "vacuum leak" and "change the switch and take a look."

 

I think it goes without saying that checking the relay is the first, easiest step; thanks.

 

The cruise is indeed the factory setup, and since I have never seen a diagram with labels to indicate for certain what it is I cannot say, but there is an electrical thingamabob on the passenger strut tower that has a vacuum line going TO it, from the purge solenoid, and then out of it into the accumulator canister, thence into the cabin. I have always known that it was a pump (why?) or something else that was cruise-related, but wasn't sure 100% that it was a pump, because its being supplied with vacuum... whatever.

 

I REALLY do not think there are any vacuum leaks... the sounds I hear when I do use the switch (turn it to defrost and heat, and it keeps my windhield clear) are as normal as they ever were, and I can hear the blender door and diverter operate and go back to neutral position when I start and turn off the car.. the vacuum switching apparatus of the switch seems to be operating fully.

 

Another possibility is that the transmission modulator is somehow causing this? I cannot see how, but the concurrent transmission problems are very hard to chalk up to this vacuum issue.. What I mean to say is, the way the trans feels it makes me wonder long and hard about how the transmission might somehow be causing this vacuum .. Problem... but not knowing jack about automatic transmissions (refuse to learn, i hate em, hate em hate em.) I don't know if that is even really possible.

 

So... basically, I need to check the relay, and if thats good and I KNOW I don't have a break in the vacuum system somewhere else, its time to rip open the dashboard. Fun times... but thats about what I had figured.

 

GD, I had a HELL of a time the last time I got into the dashboard of this car, and I even had a blast in the junkyard when I found a car that had already been ostly disassembled. There has GOT to be something I do wrong when I approach that job.. if it is so easy, what all do you do to free everything up? I know how to pop the center AC vent section off, I know where the retaining screws are.. I just cant move anything around to get access anywhere, and normally I don't have many problems like that! (Small hands and wrists, I can fit anywhere) Every time I've torn into the dash, I've gotten the impression I am missing something that would make things a LOT easier.. either unplugging something I am not unplugging, or undoing a certain screw that might not be so obvious to my Irish eyes.....

 

 

 

Thanks for the replies.