losing vacuum with heater on in RS-T

[asiahispanico]

hey guys this isnt an issue for my gst its something im trying to figure out for my girlfriend, She drives a 99 RS-T with a T3-T4 50 trim turbo. Everytime she goes to turn on her heater her vacuum drops from around 19inches to about 12-13 inches. Also when she turns the heater on full blast theres a loud click you can hear around the front of her car. Any help is appreciated!

 

[99RedGs]

The heater or the defroster? When the knob is turned to the defroster, regardless if it is on or not it engages the a/c unit. This may be the noise you hear. I don't know if this would have any effect on the vacuum though. Maybe the blower fan is going out?

 

[Twinky-Ninja]

What are the Rpm's doing when the heater comes on? If they're dropping a bit when the heater comes on, you'll lose a little vacuum. Does the car try to stall out, or is your vacuum the only noticable difference?

dave

 

[asiahispanico]

The heater or the defroster? When the knob is turned to the defroster, regardless if it is on or not it engages the a/c unit. This may be the noise you hear. I don't know if this would have any effect on the vacuum though. Maybe the blower fan is going out?

its her heater, ill try the defroster tomorrow. But its only when the heater is on full blast you can hear a loud click. It doesnt sound normal. i do know that when she got the car, it only came with the radiator fan in front of her engine. no tranny fan.

What are the Rpm's doing when the heater comes on? If they're dropping a bit when the heater comes on, you'll lose a little vacuum. Does the car try to stall out, or is your vacuum the only noticable difference?

dave

i didnt notice a drop in her rpms, it usually stays very constant. It idles a heck of a lot better then my gst. We just noticed a drop in her vacuum. its a faze boost gauge if that makes any difference.

 

[Twinky-Ninja]

I would say the ecu is adjusting idle to compensate for the extra load when the heater comes on. Unless the car starts running poorly when the heaters on, i wouldn't worry about it.

dave