AC & engine speed....
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
AC & engine speed....
What controls it or keeps it uniform when the AC kicks in?
On my '96 it is very annoying to hear the motor load up every time the AC compressor kicks on and off. It's not just at idle but through all the normal rpm range. With the AC off the idle is very good. I have checked and reset the IAC but didn't help. AC clutch maybe? Any ideas?
On my '96 it is very annoying to hear the motor load up every time the AC compressor kicks on and off. It's not just at idle but through all the normal rpm range. With the AC off the idle is very good. I have checked and reset the IAC but didn't help. AC clutch maybe? Any ideas?
Racer
Joined: Nov 2005
Posts: 456
Likes: 3
From: Sumner Texas
I have never heard any loading from an a/c compressor on a powerful, EFI V8. It makes me wonder if there is an excessive load on your compressor.
The computer deals with the added load normally by using the IAC. I don't think there is any computer input indicating the compressor clutch being engaged or anything like that.
The computer deals with the added load normally by using the IAC. I don't think there is any computer input indicating the compressor clutch being engaged or anything like that.
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
If it were a V6 I guess this would be normal. The AC cools just fine. Hard to believe it has any issues. Thanks for your input.
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
What is excessive? I have noticed if I keep the thermostat set on the high side the engine load seems less but I guess it would wouldn't it.
Le Mans Master
Joined: Jan 2006
Posts: 6,564
Likes: 6
From: Woodstock Georgia
Just get a bottle of 134 with the gauge for about $25 at an auto store and follow the directions. Simple, easy and lot better than paying a shop for what is likely just a top off charge.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Compressor engagement for your Year is controlled by the PCM and should be virtually seemless. A nano second before the PCM drives the Clutch Relay, IAC counts (air through the throttle body) and pulse width (fuel through the injectors) is increased to match compressor loading. If you're feeling it, it's usually a worn compressor or clutch assembly. Grasp the Face Plate of the clutch and see if you can turn it by hand. It's bolted to the shaft and it should turn with minimal resistance.
If you're hearing noise when it engages, check the air gap between the Face Plate and the Pulley. It should be .020 inch.
Other tests would be to observe Clutch engagement and IAC counts/pulse width with a Scaning device though most scanners are incapable of capturing data quick enough to give you meaningful info. Dealers usually rely on Mitchell software or similar which can provide real time data and graphing. You could also check operating pressures, but if you've been adding gas and no oil on a regular basis, it's probably a worn out compressor.
If you're hearing noise when it engages, check the air gap between the Face Plate and the Pulley. It should be .020 inch.
Other tests would be to observe Clutch engagement and IAC counts/pulse width with a Scaning device though most scanners are incapable of capturing data quick enough to give you meaningful info. Dealers usually rely on Mitchell software or similar which can provide real time data and graphing. You could also check operating pressures, but if you've been adding gas and no oil on a regular basis, it's probably a worn out compressor.
Le Mans Master
Joined: Oct 2004
Posts: 7,706
Likes: 485
From: Everett WA
C4 of Year Finalist (appearance mods) 2019
1) I've never notice any performance impact with the AC on at idle or any other speed. Infact unless I am outside of the car with the hood open I can't even tell when the compressor engages however ......
2) Please correct me if I am wrong here guys but my understanding is that if you have the auto climate control in a 95 - 96 and the auto feature is turned on your ac compressor is running 100% of the time regardless of the temp setting that you have the temp control set to. Point being even if you have the temp set to 80 the system is running and pushing dry air conditioned "warm" air through your vents.
2) Please correct me if I am wrong here guys but my understanding is that if you have the auto climate control in a 95 - 96 and the auto feature is turned on your ac compressor is running 100% of the time regardless of the temp setting that you have the temp control set to. Point being even if you have the temp set to 80 the system is running and pushing dry air conditioned "warm" air through your vents.
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Racer
Joined: Nov 2005
Posts: 456
Likes: 3
From: Sumner Texas
The OP said NOTHING about the compressor short cycling. He only talked about a decreasing idle when the compressor does kick in. Don't read too much into the question.
OP, do NOT mess with the a/c charge using a cheapo can of refrigerant and green zone gauge. DO NOT!!!!!!!!!!!!!!!!!!!!!!!!!!! LOTS of a/c systems have at best had decreased effectiveness, and at worst DESTROYED by these POS gauge and refrigerant can gizmo's. They are nothing but junk to take money from the unsuspecting buyer.
If the a/c is cooling fine and this is an idle speed issue, deal with the idle issue FIRST!!!!! If the a/c is NOT performing properly and you have no gauges or rudimentary a/c savvy, find someone who does.
OP, do NOT mess with the a/c charge using a cheapo can of refrigerant and green zone gauge. DO NOT!!!!!!!!!!!!!!!!!!!!!!!!!!! LOTS of a/c systems have at best had decreased effectiveness, and at worst DESTROYED by these POS gauge and refrigerant can gizmo's. They are nothing but junk to take money from the unsuspecting buyer.
If the a/c is cooling fine and this is an idle speed issue, deal with the idle issue FIRST!!!!! If the a/c is NOT performing properly and you have no gauges or rudimentary a/c savvy, find someone who does.
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
If it may be ECM related is there anything my tuner might have done that could cause the engine loading I'm experiencing? He did just a performance tune on it. I feel the car is running lean but until I get a wide band O2 installed it would be guess work to change it. The idle seems low to me at 650 rpm but it happens at any rpm.
The AC works great. I cannot believe it is low on coolant but I'll have it checked out by a shop.
Thanks for all the replies.
The AC works great. I cannot believe it is low on coolant but I'll have it checked out by a shop.
Thanks for all the replies.
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
Thanks for all of your advice!