My car has what I consider to be seriously excessive compressor drag. It's terrible. Hard to explain with words but;
*At idle in neutral, some times when it kicks on, it will almost stall the engine
*In 6th gear (the gear that you'd feel engagement the least) you can still feel it every time it cycles...both on and off. When it turns off, it feels like the car picks up ~20hp. It's huge.
*Low speed maneuvering (in a parking lot) gets trick b/c of the surge and fall of available power. Or backing into the garage, it'll nearly stall when the compressor engages, and then the engine surges when it disengages. Tricky.

When I first bought the car 4 years ago, I noticed this right away, and I figured the compressor (due to the drag and friction) would seize up in no time, and I'd buy a compressor and convert to R134a. Well that was 4 years ago and the thing is still working!

A/C experts, what do you say? Why is this thing dragging so badly? HOw can it keep working, while also creating so much drag (friction?)? And what is the recommended solution? A/C is not my area of expertise. Thanks.

 

Almost always because it's shot and when it finally blows, you will have a supersized mess to flush out of the system. The only other cause would be loss of the a/c "on" signal to the PCM. Scan it to see what's going on with that.

 

Copy. AC on signal is working (can see on my scanner) and you can hear the engine recovering as quickly as it can (which is pretty quick) when idling. But that "hit" when the compressor engages...man, it's rough.

I guess I should just move forward with replacing the compressor.

 

I would try troubleshooting it more before you shell out a bunch of money on a compressor. Is it cycling on and off so much that its causing you problems because its just low on freon?

Is the air still blowing cold? If you've had it for 4 years and it hasn't blown up yet like you thought it would, then there may not be anything wrong with the compressor to begin with.

Even R134a is approaching "LIQUID GOLD" status to be just going for a compressor change that isn't needed. Besides, there is more than that that needs to be changed when you replace the compressor.

I would be looking more at Idle Air Control. The Computer should be kicking the idle up with the AC ON.

 

I've had what I would consider excessive a/c drag on my 94 since new. This is the only car I have owned where the a/c makes such a big difference.

 

I wondered if there may not be anything wrong w/the compressor, which is why I posted. To be clear, I am not complaining about the frequency of the cycling...I'm concerned about the load placed on the engine when the compressor engages.It still blows cold. IAC works. If it didn't work, car would stall when the Compressor clutch engages.



TES. I'm glad you posted that and can relate. That is a huge reason why I posted. I mean, it's a (relatively) large engine and shouldn't be affected this way. I can't help but compare it to my '96 Silverado; same engine (basically), and in the Silverado, you can barely tell when teh compressor engages. When you're driving, you can't tell at all. If you pay deliberate attention at idle, you can hear a change in tone when it engages, but the engine doesn't change speed. NOTHING like the 'Vette at all.

 

R134 is something like 9 Bucks at Big Lots.

Check the clutch gap then or distance between the Outer Hub and the Pulley. Should be .020 inch. Ususally, if they're out of spec (too much gap), they slam into the pulley with a bang and then slip and skip. Shim kits are somewhere in the area of $12, though if it's torn up the clutch components, it's a couple of hundred (OEM) for a new clutch assembly. When it slips, it can end up with a hunting idle. I've never seen one (of my own) make it stall - until the compressor grenades.

 

Is your motor stock? Mine is not and it really don't like to idle, in gear, with the AC on. I really blame it on the cam.

 

Stock motor and it's a stick so it doesn't have to 'idle in gear" like an auto car.



Thanks for the tips. I'll check it tomorrow.

 

Tom,

the best piece of advice I can give you is to get rid of that PO$.

I dropped 30 lb of weight off my front end by removing the compressor and all the other useless parts.

We dont have traffic jams where I live (and I have no plans to ever live somewhere that does).

Its really not that bad. Even in summer, top down - sun beating down. Theres alwys a McDonalds or something where I can get a big gulp style iced Frappuchino or something of the like for my 'travel buddy' cupholder.

In all seriousness, the instant I removed A/C, spare tire, etc. my car went from a 13.1 vehicle to a 12.8 quarter mile vehicle.

 

That can be changed through tuning.

 

my 89 wasnt much different even with a good charge never understood it. Curious to hear the fix

 

Unfortunately, the '89 isn't as sophisticated as the later years in that Clutch engagement is not controlled by the ECM. Rather, assuming Electronic Air, a series of events has to take place for the Clutch to engage: The Control Panel (which is the Processor) will ground the a/c circuit at the Blower Module when a/c is requested as long as there is a completed, separate circuit, from the Control Panel to the ECM at Pin B8 and yet another completed circuit to ground through the Low and High Pressure Switches. Essentially, with all these electrons flowing, it isn't uncommon to "feel" the compressor engage and dis-engage to say nothing of what resistance may be doing to these circuits after 20 plus years.

The most common cause for a sloppy (a/c) idle on these models (assuming the Nippo Compressor hasn't given up it's shaft seal and sprayed all the lube on the underside of the hood) is a bad ECM. You'll see it with a Scan or by confirming the ECM voltage at Pin B8 (about 6 volts - or if it's absent and the compressor is engaging, you need a new Control Panel or the Circuit is grounded somewhere other than the ECM), but there won't be an increase in IAC counts or injector pulse width or those numbers are flopping around all over the place.

Later years, with PCM controlled clutch engagement, have the ability to raise idle and pulse width a nano second before the Clutch Relay is driven. That makes the operation seamless, though you're not going to see this nano second with a hand held scanner. However, all of the other symptoms; IAC counts and a pulse width that isn't responding to the load are available with a basic scan.

 

This is fantastic info. Keep in mind, this "symptom" isn't limited to just idle. On the highway, it really drags the car. If I'm climbing Parley's Canyon (SLC>Park City -3000' rise over 13 miles), my car will just about maintain my desired speed in 6th gear. There is a little power in reserve to accelerate with. With the AC on, there is NO WAY the car will make it in 6th gear. The AC kills the power. My truck, same speeds same hill, AC on or off, no discernible difference.

Another measure is mileage; AC in the 'Vette knock 3+ mpg off a highway trip. More around town. Truck? Maybe .5 mpg? Not enough to notice.

 

Sure sounds like a busted compressor - I can't imagine anything else that would create that sort of load. What does the belt look like? I've never had one be so kind on any vehicle I've owned. They've just seized and made a god awful mess. You can ask the pros on the Board at www.ackits.com - maybe one of them can come up with something else.

 

Mine has done this at idle since H/C, but dramatically worse when the air sensor, forget name on the TB gets fouled. I need to clean mine now. It drops to 1k rpm. I am going to have it to bump up more when AC is on when I get it retuned.

Just had AC worked on and they wanted to replace compressor because of drag. I explained it was due to cam and IAS needing cleaning, and has done this for 7 yrs. I usually just turn off at idle, but a pia when hot out.

 

The belt looks good, but is pretty new (<10,000 miles). When I first bought the car, I shredded the belt with the AC on during a quick WOT blast. The belt took out my CTS and plug. Replaced the belt, CTS, and two pin plug and it's been fine since.

 

I checked a few things this evening;
1. The clutch clearance is .019". I can squeeze a .020 in there, but basically, it seems like it's where it should be.

2. I started the car and let it idle for a while w/the AC on. I ran the AC on "max"(?) (manual system [C60...not C68], recirculate, full cold, full fan) for a while. Ambient temps were ~65*F. Center vent temps were between 39 and 42*F. Compressor housing was 149*F. IAC counts went from 16-20 with the compressor disengaged, to 50-53 with the compressor engaged. How does that seem?

It didn't seem bad today at all. Now I'm wondering if it is worse when the temps are higher? I'll check IAC counts again when it's hot out.

 

Tom, was your A/C converted over to 134a.. if so, I would question wheather it was properly flushed, and with the proper oil installed.. just a thought.. I can barely feel my (95) A/C ingagement during idle. If your still running R12 I would be concerned wheather there is much oil left in the Compressor,, maybe it's running dry!

 

I am a little concerned (about oil or anything else). My system is still original, running R12.