1999 Grand Prix GT No Heat

**durell81** · 01-06-2015

I know it is that time of the year when these questions flood the forum. I am posting this question now because I have tried several things and I have searched but have not found an answer. I will first describe the issue that I am having and next I will list the things I have tried and tested. Any help would be appreciated

With my heat on 90 degrees, the fan set on high, the mode set to vents I can feel warmth on the driver side but it does not blow out of the vents. On the passenger side I feel air blowing from the vents but it is ice cold.

I have read several post and this one http://www.grandprixforums.net/threa...ighlight=Blend was extremely helpful.

What I have tried:
- Flushed the radiator
- new T-Stat 195 degree
- flushed heater core (both lines on the fire wall are hot )
- My cars operating temp under normal driving is at the 1/4 mark 160 .....|.....210.....|.....260 (Torque app has me @ 195.8 F)
- I have not tried the blend actuator because I have the CJ2 digital climate control and the actuators are a little more expensive.

I believe I have 2 issues at the same time.
1. probably being an actuator because of the cold air blowing in the cabin
2. The other being a vacuum issue because on the driver side I can feel warmth or heat but it is not blowing out. Also when selecting the different modes to change from vents to floor to defrost I don't hear it change.

Please let me know if there is any more information I can provide that would be helpful

**Scottydoggs** · 01-06-2015

sounds like a blend door, as well as a vac line issue.

take the actuator off, turn the knob by hand, see if both sides blow hot air.

the air flow direction, check the vac line off the back of the intake to the firewall. that line powers the hvac controls.

**durell81** · 01-06-2015

Thanks for the quick reply ScottyD. I did trace the vacuum line from the back of the upper intake over the passenger fender well all the down past the batter and back into the fire wall. I didn't see any visual damage. Is there a way to check and see if the line is pulling vacuum?

I will have time to get to the actuator doors on Thursday post what I was able to find. If I can just solve the cold air issue I will be okay for a while.

**Scottydoggs** · 01-06-2015

ok, so you saw where that line ran into the cars harness and intot he fire wal. inside the car take the foot cover off and pull the rug down you find that line in the wire harness, it leads to a black box in the dash. it sometimes takes a crap.

when your doing the actuators, car running, watch the vac pumps, the round things in the diagram pic in the actuator how to thread. change the air flow direction, watch for the arm to move on the round pumps there. if they dont move that box could be the reason.

if they do move, check the linkage is not broken. its mostly plastic parts and they break all on their own.

**durell81** · 01-22-2015

At this time I still haven had a chance to replace my passenger side actuator due to my work schedule and things going on with the family. Luckily the weather broke here in TN and it hasn't been to cold. I was able to get by the Junk yard near me and pull a few actuators from several GP's. I popped them open and checked the gears to see if any were broken and only one had a crack. So all I have to do now is install one of the good ones to see if solves my cold air on the passenger side problem. Hopefully no family emergencies this weekend.

I also have another question about the HVAC fuses. I was checking the fuses in the glove box and noticed that the "HVAC CTRL" fuses was missing. Does any one know if this fuse would have an effect on the "Mode" cntrl which tells the HVAC system to output to the Floor/Vents/Defrost?

I have searched on the forum and found that a lot of GP's are missing this fuse and everything is working fine. Just wanted to hear from anyone who may have it installed.

**durell81** · 01-26-2015

Replacing the actuator fixed the driver side hot and passenger side cold issue. No the car gets nice and hot. I still think there may be a vacuum issue the reason the driver side heat does not blow out of the vents.

**BillBoost37** · 01-26-2015

There is a vacuum controlled part .. it comes off the ehhhh look at the passenger strut tower. There's a vac lines that crosses over it and heads down under the bumper.

BTW, does this car hate you?

Thread: 1999 Grand Prix GT No Heat

Thread Tools

Display

Bookmarks