I have an interior heater issue on my 2004 db9. This morning it would not blow warm air. The engine warmed up nicely and i have no issues on motor temperatures but the interior air is ice cold even when turning of the AC putting the fan to max heat and max blow.
It all looks to be working ok except that there is no hot air coming in. The strange thing is, when i stopped to get some fuel, and restarted the car, it started to blow warm air again.

Coolant level is ok, motor temp is ok (so i guess no thermostat issue). What could it be/what could i check first if it happens again?

 

i had a similar issue and despite temp gauge info that looked normal, the thermostat had failed. i know it'f a VERY common issue in the early 2006-2008 vantages.

alternatively... the HVAC systems in cars these days involves a rat's maze of plastic passages under the dash that route hot and cold air to the vents using doors that open and close using little electric motors. those doors can get stuck open, closed, and halfway open. additionally, the hinges on those doors can fail leaving them to flop open and closed subject to inertia. i sincerely hope that is not the issue, for if it is, although a straight forward item to fix, it can be expensive.

although a thermostat replacement may initially sound unappealing, it is preferable to HVAC problems, IMO.

let's hope i'm way off base and it's something i've missed. i do that a lot!

 

Driving home it worked like it should, so I hope it stays away but I guess it will not (knowing the car). I wanted to do a full coolant flush somewhere soon, I guess I can take the thermostat allong anyway. Just to make sure.

If anyone alse has ideas I'm still open for advises if someone thinks it's something else.

 

yes, if an obstreperous dog lies down and goes to sleep, it's best to just leave it alone.

 

On LH drive cars there are two servo motors down above the throttle pedal towards the center console.
You can stick your head down and look up from the floor and you will se them. The two servos look like half-palm-size black boxes which have an arm with a steel rod linkage.

The top of these two motors is for the mixer valve, ie. it moves a flap to direct the air towards the heater core or just around it.

On my Vantage this servo would stick when it was selecting cool air, and if I gave it a bump with my finger it would move again. I removed this servo and opened it up, there is a small motor with gearing inside aswell as a potentiometer track on the circuit board. When the servo is moving a shoe moves along the track which has variable resistance. This resistance is passed to the HVAC control unit as a position of the servo.

After cleaning the track and giving it careful wipe with some scotchbright (also the shoe ofcourse) I was able to restore this servo to proper function.

If this happens again, try reaching up and give it a nudge. If it moves and the heating starts to work again, you know where the problem is.

Photos of servo:

Complete servo. To remove arm from shaft just push in the litte clip and pull it of. Plastic tabs around the perimiter keeps the lid on, just pry them open. and remove the lid.

Inside servo. The big plastic gear have the shoe and the pcb with the track hidden under it. Try bending the shoe down a bit too to make sure it contacts the track firmly.