512TR Climate Controls

Ron -- I can empathize with you -- they're not well explained in the TR documentation either (I finally figured out that more LEDs "on" means the motorized vent flaps on the sides at the bottom of the AC unit itself, letting some air into the footwells, are more open). I'm only guessing that your 512TR is the same as a TR, but have a look on the sides of the AC unit towards the bottom to see if there are motorized vent flaps for letting a little air into the footwells (the air volume discharge from the main vent doesn't change much on mine whether the footwell vent flaps are open or closed).

 

My 86 TR has a similiar set up. Mine works great. The more gold bars that are lit up the more cfm of air comes out in the footwells. Air at the dash vents is constant reguardless of how much comes out at the bottom.

My fan speed switch doesn't work properly, the hvac system either blows at full speed or does not blow at all.

 

khayes -- your TR blower behavior (full "on" working, but no slower speeds) is a result of a failure in the slow speed controls. The TR AC blower has two modes of operation:

1) when full "on", the knob control box is just a simple on-off switch, that when closed, closes a relay that puts +12V on the blower motor and runs it at full speed (yours is OK in this regard).

2) at any speed below full "on", the knob control box has a second, more-complex section that supplies a small variable control current to a power transistor which, in turn, controls the amount of current allowed to flow thru the motor (giving the variable speed).

It's possible that the electric gizmo function of the knob control box for variable speed is bad, but it's much more likely that your power transistor is kaputt.

Sorry if I've said all this before, but any shop dealing with TRs will have a lot of experience with this -- it's a common failure IME

 

Thanks for the information Steve. The previous owner mentioned that he replaced the "knob" once and it broke again within weeks. He said that it was a common issue. He also mentioned that someone in Houston came up with a solution in the form of a personal computer fan mounted near the switch to keep it from overheating. I would like to get mine fixed. It sure is annoying but this time of year it's a low priority for me since its now in the 90's every day.