Another Heating Question...

[felis_filia]

HI, i'm new to the forum. I've read previous posts on heating problems in trans sports. i had a clarification question though. the rear heating vents work. the front don't. is that the switch that needs replacing or something else. any help? thanks.

[LMP]

Some more questions before any idea:
1- Does the front motor works, when you switch the blower to different speeds, do you hear it at all speeds, or only some, or not at all? If the motor does not rotate, disregard the other questions.
2- If motor rotates, does it make any difference that you go through modes: VENT, FLOOR, DEF, or does the air blow always from the same outlet?
3- If motor rotates and you get some air through various outlets, do you mean that you get a very little amount of air?

[felis_filia]

the back vents work on all speeds. the front do not work at all. there's no sound from the motor when trying the front vents.

[felis_filia]

you can feel the heat from the front vents, but there's nothing pushing it out. on any speed, or def, etc...

[LMP]

OK that looks like motor is dead...or is not fed 12V...

www.avigex.ca/xport/hvac_heater.jpg
First check HTR/A/C fuse 25 amps in the fuse block (glove box) just in case (according to my '93 diagram, if this fuse was dead, the rear would not function but there might be slight variations in design).

IF fuse OK, next in line is the lo speed relay in the convenience center. www.avigex.ca/xport/convenience_center.jpg but if it was bad, the rear heater would not work either...so next is the high speed relay and then the blower motor itself:

www.avigex.ca/xport/heaterrelay.jpg

THe motor can be easily disconnected and fed directly with 12 v to test it.

If it rotates on that test, then the high speed relay may be damaged because even in low speed, current passes through it too.

EDIT: IT MIGHT BE EASIER to test for 12V at the connector disconnected from the blower motor instead: connect a voltmeter then turn the heater switch on to any position (with ign. key ON) and you should read 12V on all settings.
IF no feed, change the HI speed relay (BOSCH 12077864 800 on my '93)
If 12V is there, change the motor.

[felis_filia]

ok. we'll give it a try. thanks a lot!

[felis_filia]

everything is fed 12 V so does that mean a new blower is needed?

[LMP]

IF this is your findings, then remove the blower, and just in case - once removed test it again with 12V from the battery or from a hefty battery charger (well a small charger will do, but it would not rotate fast). This will certify once an d for all you have found it, and at same time you have the model in your hands for a replacement. (an easy find in scrapyards).: TEST IT before installing.
With most blowers, using the HI SPEED for long terminates life in a limited amount of time: all of these motors smell burnt wire at HI SPEED" . Better use HI only for limited time once engine is real warm then "downshift" blower to 3rd speed. When on COOL , this means the air that serves coolong the motor itself is much warmer than in winter..so using HI for long periods is even more damaging.