Hello, I just recently purchases a 1999 sc400 and for some reason my heater and ac work when in park, but when I put the car in drive it stops working. Anyone know what it could be? Thanks

 

is the car lowered? if yes have you relocated the wheel well harness?

 

I believe the car is stock height, as for the harness im not to sure. Previous owner said it worked before but the car sat for a year until i purchased it recently

 

I don't have a link handy, but search for pulling the HVAC trouble codes (similar to CELs), to see if there's any hints there. I'm not sure if '96+ retrieves those through OBDII or if they're still done through the earlier manual method.

I can't think what connection the transmission mode and HVAC would have.

 

When the heater stops blowing hot in SC's one of the common causes is being low on coolant, check the coolant overflow reservoir and fill it up.
Happens on these cars when it gets low and maybe putting it in drive affects the level or speed it's circulating etc..
Not sure why the A/C would stop working though, so maybe something else is going on.

 

The Ac/Heater unit just shuts off completely when put in any gear. Only turns on when its in park for some reason