Trying again - A/C compressor engaging while in VENT position. Keith??

[glock35ipsc]

I posted this last year, but got nothing, so I'm gonna try one more time.....

The A/C compressor should engage when the switch is in either the MAX, NORM, or BI-LEV positions, as well as the DEF position.... all of which are happening, so all is happy there.

But the compressor should not engage in the VENT or HEAT position.

The VENT and HEAT positions are under the heading of ECONOMY for a simple reason.... it is simply circulating air while not running the compressor, and no de-humidification is required. The problem with Fred is that the compressor is engaging in the VENT position. So when it is nice and cool out in the mornings, and I just want to bring in some cool fresh air, I can't because the compressor is running. So, essentially, I'm running in the NORM AC mode when the switch is set to VENT. It is not engaging the compressor while in the HEAT position, which is how it should be.

So, do I just have a bad rotary selector switch in my panel, or is there some other electrical issue I need to be looking for?

[MONTEZ]

Nevermind. My post didn't make sense.

[Dropped84GMC]

i could understand what you ment... sounds to me like either the switch is bad either a short across from the bi-lev to the vent or the little arm inside is bent abit

[glock35ipsc]

I understood what you meant too, and I alluded to it in my post. But yeah, either the switch is bad and/or has a short, or I have a gremlin somewhere else!

[geeforcem]

bad selector switch.. easy fix!

[swb85]

Interesting.....this JUST started happening in my truck last weekend!! Used to work just fine on VENT, but now the compressor is engaging all the sudden. New switch is the fix then? Let me know what you do to fix it!

[Slonaker]

When I posted the same question several years ago, I was told that the switching system in the unit pictured above was bad, and it was easiest to replace the whole thing. I purchased one locally from a parts store that carries AC Delco parts. I was quite surprised to find that it was not a dealer only item, or unavailable. I paid less than $50 for it, an even bigger surprise for a genuine Delco part.

One of these days I'll install the thing and find out if it was really the problem!

Slonaker

[glock35ipsc]

Cool, so the consensus is the switch. That's good in that it's the easiest fix, no chasing wires. But it stinks in that I have to pull the bezel off, and I hate doing that! That means I have to bend all the little tabs on the stereo housing to get it out before I can pull the bezel off. Oh well, now I'm just whining!

Thanks guys! I was looking for some confirmation on this before I tear into it.

[Desert1957]

There is one other thing to check. Some A/C compressors but not all ,had a little diode at the plug where it goes into the clutch coil. the purpose of this is two things. when the engine is turned off with the a/c on , it lets the voltage drop to zero at the clutch, preventing battery drain. The second thing it does is effect normal clutch operation, In my experience when I have seen a diode go bad ,the A/C clutch clearance, if it drags a little , between the coil and the pulley makes a magnetic field of its own which causes the clutch to engage anytime the engine is running. even with the switch off.
The diode in qustion was mainly used on (R4) style comressors , Not the large (A6) Style.

Desert

[glock35ipsc]

Originally Posted by Desert1957

There is one other thing to check. Some A/C compressors but not all ,had a little diode at the plug where it goes into the clutch coil. the purpose of this is two things. when the engine is turned off with the a/c on , it lets the voltage drop to zero at the clutch, preventing battery drain. The second thing it does is effect normal clutch operation, In my experience when I have seen a diode go bad ,the A/C clutch clearance, if it drags a little , between the coil and the pulley makes a magnetic field of its own which causes the clutch to engage anytime the engine is running. even with the switch off.
The diode in qustion was mainly used on (R4) style comressors , Not the large (A6) Style.

Desert

I have a 5.3L in my 85, and the compressor is original to the engine (a 2006), and I applied new Weatherpak plug on both ends, so that probably won't apply here. But it is good info to have though, thanks!

[trevor73402]

I have a very similar problem. In my '84 K10 I cant get the compressor to ever go off except on "vent". When I slide the lever to the "Off" position the compressor still continues to run non stop. The vent position is the only place I can get the comp to stop running so I have to have the vent blowing all the time no matter what. Also I dont think the compressor ever "cycles". It seems to run non-stop.

Any suggestions?

[92470]

I had a similar problem with my 87' V10, except the compressor would not engage on the a/c settings. After much troubleshooting, I took the control panel out and noticed that the rotary switch inside that roates when you go through the settings was corroded and not making contact. One area of it actually had a burn mark on it, so moisture got in it some way and wrecked havoc. I just went to Pick and Pull and pulled another control panel. It was like $10 and fixed my issue. One I pulled looked new with no scratches also, so double bonus. You can find used ones on eBay also. I bet that's your problem. Good luck