Electronic A/C acting wierd...

[dmd]

My electronic A/C when set to "Auto" always starts out blowing from the defroster vents and under the dash. Then after 5-10 minutes it starts blowing out the main vents. If I shut off the car even momentarily the whole cycle starts over again. Is this how it's supposed to work?

Dave

 

[lt4 gs]

I assume you r talking about your lt4?

 

[dmd]

Yep, the LT4.

 

[Fick]

I don't think thats normal. Mine blows out of the main vents right away.

 

[B17Crew]

There have been a number of posts on C4 AC oddities. I have one of the links that I found in the Search function posted below. Not quite the same problem, but it may help get you started in finding the culprit.

It doesn’t sound normal, I’m pretty sure you should have air directed immediately from whatever option (windshield, mid-level, floor) you choose on the electronic climate control.

http://www.corvetteactioncenter.com/forums/showthread.php?s=&postid=89125#post89125

Please keep us posted.

B17Crew

 

[dmd]

Thanks, I'll take a look at it and report back.

 

[B17Crew]

You’re welcome!

B17Crew

 

[Vettelt193]

what happens when you run wide open? Typically, that problem is associated with a vacuum leak and the air will redirect to the defrost vents under full throttle too.

 

[jcs44]

My LT4 does as described as well in the "auto" mode. Pushing one of the buttons for floor or dash will put in manual mode with AC off. In auto, it first blows mostly through the defrosts for about a minute and then shifts to mostly dash vents, although some air is still coming from the defrost and a little to the floor. You all sure this isn't normal for this HVAC system?

JCS44
Triple Black Vert

 

[B17Crew]

My LT4 does as described as well in the "auto" mode. Pushing one of the buttons for floor or dash will put in manual mode with AC off. In auto, it first blows mostly through the defrosts for about a minute and then shifts to mostly dash vents, although some air is still coming from the defrost and a little to the floor. You all sure this isn't normal for this HVAC system?

JCS44
Triple Black Vert

Not sure, I’ll have to try mine this weekend and time it in AUTO mode... 5-10 minutes for dms’s LT4 is seems like a long time. My ventilation system seems to react fairly quick after selecting a particular mode... so far :ugh.

B17Crew

 

[dmd]

That's exactly how mine behaves, even shutting off the A/C when I manually select one of the other vent configurations. It seems to vary how long it takes to switch over to the front vents based on how hot it is. As it's been getting cooler here in Chicago the past week or so, it only takes two or three minutes to switch over now. It's mostly just annoying as it makes the windshield mist up depending on how humid it is. I'll probably be checking the items suggested in the other thread tonight (had some higher-priority car projects to finish first this weekend) and see what I find.

 

[B17Crew]

I’m in Columbus Ohio, could have to do with ambient temperatures as you’ve suggested. We haven’t had any major swings in temperature, so maybe that’s why my system seems to react in under 5-10 minutes.

B17Crew

 

[Vettelt193]

That's exactly how mine behaves, even shutting off the A/C when I manually select one of the other vent configurations. It seems to vary how long it takes to switch over to the front vents based on how hot it is. As it's been getting cooler here in Chicago the past week or so, it only takes two or three minutes to switch over now. It's mostly just annoying as it makes the windshield mist up depending on how humid it is. I'll probably be checking the items suggested in the other thread tonight (had some higher-priority car projects to finish first this weekend) and see what I find.

what happens when you run full throttle though? anything change?? the A/C is hooked into the vac system and if there is a problem with that, it will be noticed under heavy throttle usually rather quickly.

 

[novafink]

Mine does the same thing also, 96ce lt-4, I was told by someone, it is a bad switch somewhere, but it doesn't bother me too bad.

 

[96BayouLT4]

My A/C was doing the same thing, it would always blow air to defroster and some to the floor. As noted in above link I pulled the unit out thats located above the gas pedal, what a pain. Next time seat will come out also.

If I had to do it again I would add onto the vacuum hoses, especially the tan one so I could get to the unit better. This control unit houses the relays that control the vent flaps when you select them from the master panel.

I noticed when I removed the front side vacuum hose plate that there was still vacuum present which told me that the unit was not leaking and at least I was getting vacuum to this location.

The problem I would bet is the rubber tips that are attached to the housing are partly closed from years of use and not allowing the vacuum to get to the manifold that is connected inside the control unit, this would account for the delay some of you'll have experienced. These tips slide into the plate/block you will have to pry off. I used a paper clip and opened up the rubber tips, reassembled it all using a 8-32 machine nut (7mm socket) to hold the front side vacuum hose assembly on. When I started it up, presto I had air out the dash vents for first time in 2 years.

I hope this is the end to it but suspect the rubber tips/ends will close back up again, but next time I will take a razor blade and slice off the very top of each one and I'm sure this will cure the problem.

Bill

 

[wx briefer]

Actually, I fixed mine by the repacing the controller as suggested in tech tips on this forum. But, really, it may have just been the fact that after repositioning the hose manifold on the controller, whether using a new or same old controller, the seal was then intact and therefore functioned perfectly again. If I were you, I would just remove the manifold on the controller and reassemble making sure to tighten the hold down nut really well and see if that fixes it.