heater and ea/c problem

[clean95]

ok kinda strange, the heater and a/c work but only when im driving if i come to a stop idle or low rpms the heater will not blow hot just vent outside air same with the ac will stop blowen cold and back to vent air.... then when i stomp on the gas or on the free way its fine or just cruisen the streets its fine only f*&$es up at stops or low idle.... weird? any one have this problem befor?

 

[96ProCompTahoe]

have you changed the coolant lately? i read on a thread awhile back that you can develope a bubble in the lines and cause no heat.

Not sure why it would just do it while sitting still and not while driving.

 

[clean95]

ya i have im thinking its a vacume problem because vacume is only applied at idle or low rpms and isn't used during driving or cruising speeds just seeing if anyone else has had the same problem.. weird tho