2000 blazer idle surges in conjunction with ac compressor cycling.only until full operating temp,idle surges from 600 to 1100 rpm bout every 10 seconds or so but only in ac or defrost mode.if in heater mode only,no surge.could week alternator cause this?when rear defog on lights seem to dim somewhat.
any ideas?

 

pulled compressor relay-problem gone
maybe system just need recharge?
oh well,cold out anyway

 

Defrost uses AC Comp too welb - might need that in Winter...

Loping idle (up / down idle) about 99% sure is a vacuum leak. I think most AC settings use vacuum that's re-directed to controls BEHIND the dash; some are underhood.

No loping withOUT AC on?

 

defrost blowing good heat and all without a/c cycling so good enough for now?thanks