The heater blower on my 1992 previa keeps going off and on. I replaced the risistor for the motor because it was cracked nad the problem continues. It will work fine for a day or two then it will not run on high speed. I take it apart it starts to work and nothing I do makes it stop. Where can I find a diagram of this circuit?

SOURCE: PREVIA 1992 NO HEAT

If your Previa's low/medium speeds on the blower (ac/heat fan) have stopped working, but the high speed works, you most likely have a problem with your blower motor resistor. Here's how to access the resistor. These directions may be slightly incorrect since I finished this procedure about an hour ago and I'm typing this from memory. But they should get the job done. It took me about 30-40 minutes to do this from start to finish:

Remove cabin air intake duct (two philips screws)
Remove one bolt holding antifreeze reservoir in place, move reservoir aside.
Remove two bolts holding brake fluid reservoir in place, move reservoir aside.
Unsnap recirculate/fresh selector cable from blower housing (on vehicle-left side of housing)
Remove angled metal arm from vehicle-right side of blower housing (attaches to firewall with nut and to housing with bolt).
Remove two bolts (at vehicle-front of housing) that hold the upper and lower blower housings together.
Remove nuts on firewall holding upper blower housing in place, and begin to work upper housing out of vehicle, disconnecting the 4 electrical connectors as needed (2 connectors are on top and 2 are down beneath the blower housing).
Remove nuts on firewall holding lower blower housing in place, and remove lower blower housing from vehicle

Look on the lower blower housing, on the side which was facing the firewall, and you'll see a white ceramic block (approx 2-3 inches long). This is the blower motor resistor. There are 2 contacts on the resistor that should be joined by a springy curved band. If the band isn't bridging the two contacts, it's likely that the soldier has melted/broken, and this is what's causing the low/med speeds to not work. Solder the band back in place and this should correct the problem (it did for me).

SOURCE: I have a 1992 Toyota Previa. The heater stopped

the last year, your blower resistor has been bad, now your motor is bad. rap on the motor and see if it start to run, if so, replace the motor and the resistor.