Ac/defrost question. 99 gt

[Noboostedgt]

So I have a 1999 gt and when I turn on the Air conditioning or the defroster the engine really bogs down. It will almost stall at idle when it kicks on and feels like it loses 50hp when driving. I just wondered if anyone else has had any issues like this.

 

[KRUISR]

The bog is when the A/C compressor kicks on. The A/C compressor will cycle for all HVAC positions except Vent. In winter it comes on to dehumidify the air for our defrost (this is for us guys in the north that need heat on the windsheild) mode. You either have an issue with the compressor or whatever normally bumps up the idle when the compressor cycles is not functioning properly.

Just my thoughts

 

[manicmechanic007]

Noboostedgt, You have not modified the serpentine belt or pully system right?
10 horsepower is supposed to be the AC compressor draw
The processor is supposed to control the idle well enough for you not to notice this draw much
However most cars do just what yours is doing
Yes it is worse when the compressor is getting tight and ready to seize
Also the hunting for idle seems worse when the freon is low and it cycles the clutch too often
Chevtone puts a heavy metal "frisbee" on the waterpump of some motors to solve this issue
My 1990 Corvette has the factory frisbee on it still

 

[manicmechanic007]

The frisbee adds weight to the accessory drive system
It is an additional heavy flywheel on the waterpump that most owners have removed for quicker acceleration

 

[Noboostedgt]

The bog is when the A/C compressor kicks on. The A/C compressor will cycle for all HVAC positions except Vent. In winter it comes on to dehumidify the air for our defrost (this is for us guys in the north that need heat on the windsheild) mode. You either have an issue with the compressor or whatever normally bumps up the idle when the compressor cycles is not functioning properly.

Just my thoughts

Also when I bought the car and

Noboostedgt, You have not modified the serpentine belt or pully system right?
10 horsepower is supposed to be the AC compressor draw
The processor is supposed to control the idle well enough for you not to notice this draw much
However most cars do just what yours is doing
Yes it is worse when the compressor is getting tight and ready to seize
Also the hunting for idle seems worse when the freon is low and it cycles the clutch too often
Chevtone puts a heavy metal "frisbee" on the waterpump of some motors to solve this issue
My 1990 Corvette has the factory frisbee on it still

No it has the original pulleys on it. Also when I bought the car 5 years ago,the guy had installed a aftermarket cooling fan and for some reason had tapped into the ac pressure switch for the power supply. Not surprisingly the fuse was blown so ac/and defrost didn't work. I just wonder if anything other than the fuse could have been damaged. Thanks to everyone for the answers. Also yes I fixed the fan and wiring which all works fine.

 

[Mustang5L5]

The “kick” on the compressor on the new edges is pretty significant. It’s much more pronounced than the newer cars today using variable piston compressors to lessen the drag on the engine when not needed.

I bought my 03GT new, and when the ac came on you felt it. Felt like you lost 100HP. Cooked great, but robbed a ton of power. I’ve never had a car since that was like that