Jadz928

I did a quick search and didn't come up with a quick answer. Just went thru my HVAC and fixed a couple acuators. At the same time figured it would be best to replace the fan speed control switch. You know, the one that causes the "magic blower syndrome".
Well everything works as intended except my fan speed only blows at one speed, max.
I know I could put the old unit back in to test. I guess I just don't understand why the new switch doesn't work. Am I missing anything here? Thanks!

Lizard928

resistor pack in heater box,

remove the hood, then the blower motor, then you can reach in and hold it to be able to undo the screw and remove it.

Rod Underwood

The resistor block is bad. That was exactly what mine did and I've read the same story with others. It's a bit of a pain to replace - remove the fan and reach inside to grab it. The plug is on the outside and the two screws as well.

Good luck,
Rod

Jadz928

I'm sorry I didn't use the correct terminology. The resistor pack is what I replaced. I believe it uses the coil resistors to control the fan speed. So I have a new unit in there and it doesn't work. I'm stumped, unless the unit is bum.

Rod Underwood

Can you plug it in outside the air box and see if it responds in any way to switch changes? or if it changes under any conditions?

Rod

Lizard928

I cant remember which relay it is on the fuse panel but one of them supplies power to this area, try bridging that relay and see what happens, i know mine worked only in defrost which povided max fan, but wouldnt work on anything else, I swapped that relay and it all came back.

Alan

There are 3 versions of the resistor pack - only the earliest version (NLA new I believe) will work unmodified on your car.

There is a '78-'88, '89-'93 & '94-'95. The '94-'95's are rare

If you have the most commly avalable '89-'93 version you can modify it to work. I believe I explained how in a post of a year or two back... maybe in more detail...

Anyway here is a summary:

Pin# --- Function <’89 --------------- Function ’89-‘93
=========================================
1 - Speed 1 input from Switch ------ Speed 1 input from Switch
2 - Not Used (Same as 6 below) --- Not Used – (Same as 6 below)
----- (Output to Blower) ------------ (Output pre-thermal protection)
3 - Unused ---------------------------- Unused
4 - Blower Relay In (on all speeds) - Blower Relay In (on all speeds)
5 - Speed 2 input from Switch ------ Speed 2 input from Switch
6 - Output to Blower Motor --------- Output pre-thermal protection
------------------------------------------ (not used – same as 2 above)
7 - Speed 3 input from Switch ------ Speed 3 input from Switch
8 - Blower Relay In (on all speeds) - Output to Blower Motor

So to enable a '89-'93 version to be used in a <'89 you need to remove the existing car side wire connection to Pin 8 (leave disconnected) and swap the motor connection from Pin 6 to Pin 8. This can quite easily be done in the socket.

Alan

RyanPerrella

something i randomly discovered.....

Replace the "relay x" with another one of your relays. (its the common "53" relay) I did this and suddenly my blower motor worked in all 4 positions. You may want to switch your relay x with another relay and see if that helps at all. It may not be the resistor.

j.kenzie@sbcglobal.net

What Alan said.
I did this by switching the wires in the plug to the resistor pack. I found instructions for the wire swap here and on Nichols tip site.

Jadz928

Thank you Alan and Dave. Funny, I did check Nichol's site before posting. Must've missed it as I was in a hurry. I appreciate your help.