A/C blower motor problem

curtis73 · #1 10-11-2005, 09:45 PM

I'm having trouble tracking down a little issue, and the fact that 1) I know very little about A/C wiring, and 2) I don't have a wiring diagram... makes it a bit tough to diagnose. This is in my 73 Impala Station wagon.

The fan works fine on 1, 2, and 3, but not on four. I replaced the fan relay with no change, and replaced a corroded inline fuse with no change. By default at all times the fan remains running on the #1 setting. That is how its designed, even if the systems is off.

So, mine is operating like this: With the system off, the fan runs on 1 as designed. With the system on, the fan will run on 1, 2, or 3 when I select those settings, but when I put it on 4 it stops... not returns to 1 like the default would suggest, but off. I'm getting clicking and voltage to the relay and the relay tests fine, but no operation on 4. On the other settings I get 4, 6, and 9 volts, but when I put it on high I get no voltage.

Thoughts?

Moppie · #2 10-11-2005, 11:32 PM

Replace the switch

Common problem on a lot of older style blower motor swtichs as they use and old style rehostat to control current flow to the motor and control its speed.
Quite often part of the rehostat will suffer a fualt, or get covered in dirt etc in one of the switch positions.
You could try cleaning it, but replacing it is the safest option.

sierrap615 · #3 10-11-2005, 11:44 PM

for blower motors, its not uncommon for the HI setting to feed from a second power source, typicily one with a higher fuse rating and higher gauge wiring. i have even seen one or two that use a fuseible link for high. my school's resource center has some dusty old books, i see if i can find a wiring diagram.

curtis73 · #4 10-12-2005, 02:36 PM

Moppie, the resistor pack is a separate thing located inside the evaporator box to keep it cool. It tests fine and controls 1-3. There is a relay that kicks on when you select 4 (or high) and just feeds 12v directly to the fan. So in this case, the switch just has four separate outputs all at 12v. It feeds each circuit into the resistor pack after the switch. I really need to test the switch, but I don't know which one is which yet. I'm hoping a buddy has his shop manual available to let me know the pinout. Sierrap615, I tested that circuit with the inline fuse and got full voltage. Its giving 12v to the game and its sourced from the horn relay, and the horn works

I did find a couple wiring diagrams today online that didn't really apply to my car, but they were a similar design. Armed with that knowledge I'm going to re-check some things today and get back to you guys.

Thanks for the help.

Moppie · #5 10-12-2005, 05:27 PM

They never make these things easy do they.

Good luck with, and let us know what you find.
I still think it will be the switch thats broken

sierrap615 · #6 10-12-2005, 06:36 PM

Quote:

Originally Posted by curtis73

I'm hoping a buddy has his shop manual available to let me know the pinout.

wouldn't you know? i found the wiring diagram and traced out a copy, but i didn't copy the pin-outs.

i will get it tomarrow.

curtis73 · #7 10-12-2005, 09:49 PM

Actually, call off the search. I found the problem. Of the four relays I had (one new, two junkyard, and one left over from a different project) None worked. One didn't energize the primary coil, two didn't provide continuity where they should have, the new one worked but provided about 60,000 ohms

No wonder the fuse was crusty.

Thanks for the help and we can call off the search.

Moppie · #8 10-12-2005, 11:13 PM

So we can return to DEFCON 1?

TheSilentChamber · #9 10-12-2005, 11:53 PM

All of this and you dont even tell use what make/model/and year it is! you bastard!.

fredjacksonsan · #10 10-13-2005, 01:56 PM

Quote:

Originally Posted by TheSilentChamber

All of this and you dont even tell use what make/model/and year it is! you bastard!.

See other posts/Curtis' website to see full details about "The Wagon Restoration"

curtis73 · #11 10-13-2005, 11:27 PM

Quote:

Originally Posted by curtis73

I'm having trouble tracking down a little issue, and the fact that 1) I know very little about A/C wiring, and 2) I don't have a wiring diagram... makes it a bit tough to diagnose. This is in my 73 Impala Station wagon.

Hmm... somebody didn't read the whole post

I think Defcon 2 to be safe. It ran fine today, but I don't trust it yet.

TheSilentChamber · #12 10-14-2005, 03:53 AM

holy shit, I need to lay off these mystery pills, and the damn viagra is making me go blind.

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