I recently purchased a 1970 cutlass. The fan doesn't work, how can I test to see if it's the fan or the control switch that is broken.

The heat/AC fan speed switch doesn't click through the steps from slowest to fastest speed, it slides. Is this normal for 1970, it wasn't in a 1977 or 1986 GM car that I owned.

Thanks for the help.
Jim

 

Go by a $10 test light and poke around a little.

 

The obvious first step is to pull the wire at or near the blower, and see if it has any voltage when it should. It's common for the brushes to simply wear away in the motor.

 

how about the switch in the car, should it slide up and down or have 4 distinct positions?

 

I am not familiar with that model so much, but if there is no voltage at the motor, that would be a good thing to look at next. Maybe take a peek at it under the dash and see if it has obviously fallen apart. Buy a new switch for general principles, and see how it feels? A good thing to have a spare of either way.

 

Hey Jim, I went out in the shop to make sure and mine has 4 distinct "detents" in the switch; Off, Lo, Med, Hi. Good luck with the diagnosis!

 

Thanks guys, I will take a look tonight.

Jim

 

This is correct. Also the same detents are in the AC fan switches.

 

Yeah, the good thing about the GM blower systems is that they were essentially unchanged for over 20 years, so whatever you know about the '77 or '86 probably applies pretty closely to the '70.

And I've never seen one of those switches just "happen" to lose its detents - I'd imagine someone took it apart.
Keep the pieces, as it is likely that you can put the internals from a different year into yours in case you have any trouble finding just the right lever, etc.

- Eric