Why does my engine lose power when I turn on any of my heat climate controls? on 1998 Chevrolet Express 2500

It seems to make the motor click and then lose power.

Asked by for the 1998 Chevrolet Express 2500
agree with prof.
2 more answers , 4 more comments
agree with prof.
What do you turn on when this happens? Defroster?
Yes defrost on low or high
Does your A/C work. Is compressor good.
No..not that great...
Was thinking compressor might be locked up. When the defroster is turned on the compressor also comes on. If your controls are bad during the other settings the compressor might be triggered as well. Should be no other reason for you to lose engine power with heater function. Sorry if I didn't help. If I was close I would check it for you. Need to have someone check it.