HVAC Blower Motor only runs on high

In my '90 GT the HVAC Blower Motor only runs on high. I am wondering if anyone knows it this a control issue (is there a resister pack, etc.) or a blower motor issue?

It is going in for service next week;
1. Fix the A/C not working issue (died after a complete replacement 2 years ago)
2. Find electrical drain(s) Battery gets run down after just a few days of sitting.
3. Find out why it goes into some kind of limp mode, even with IGR bypass relay in place (new ignition control units, coils, dist. caps, dist. rotors & plugs. Wires are just a couple of year old Magnecor. The manifold refresh with most parts replaced was done 2 years ago).
4. Review HVAC blower only runs on high issue.
5. Review ball joint, as they noticed a boot tear last time it was in.

My 87 has started doing the same thing, however it is intermitent. Some days all speeds work and others just the high . I'm hopping there is a module to replace as was done on my GMC pickup. The pickup was an easy fix . Hope thecar is to. My AC is not working but it is not in the cards this year (needs new compressor) .This should not affect the blower settings.

87 Shark;4255 wrote: My 87 has started doing the same thing, however it is intermitent. Some days all speeds work and others just the high . I'm hopping there is a module to replace as was done on my GMC pickup. The pickup was an easy fix . Hope thecar is to. My AC is not working but it is not in the cards this year (needs new compressor) .This should not affect the blower settings.

Thanks, yes on my M3 it is supposed to be a Final Stage Unit, about $60, so hoping the 928 has something similar.

Yes, I know the A/C problem is unrelated, rumor is that the clutch in the Griffiths kit dies quickly

Stan, The power to the blower goes through the resistor pack that controls the speeds.
If the motor starts to drag or draw to much it burns them out one at a time. The high speed has no resistor and is driect power that is why that speed still works.
The resistor can just be old and burn out as well.

928mac;4259 wrote: Stan, The power to the blower goes through the resistor pack that controls the speeds.
If the motor starts to drag or draw to much it burns them out one at a time. The high speed has no resistor and is driect power that is why that speed still works.
The resistor can just be old and burn out as well.

Looks like a fun project: members.rennlist.com/pirtle/svc.html

Isn't this (or something like it) known as Magic Blower Syndrome?