Fan Issue - Thermo Switch or Relay?
 

My cooling fan stops working intermittently in my 84 NA. Is this more likely the relay going bad or the thermo switch? Should I just replace both?

I've seen far more failed relays than failed thermo-switches. Given that, and the fact no coolant is lost when changing a relay, I'd probably start with that one. Just my $0.02.

If you don't know how old that switch is I'd replace it as well. I'm a big fan of treating repair work systemically. Kind of like you'd never pull a control arm and replace the bushings, but not the ball joint.

Uh why are you guessing? Diagnose what isn't working. See Clark's Garage for the how to.

Guessing only because the problem is intermittent. I drove to work, fan wasn't working, drove home fan started working. It will go for days working fine then out of the blue stop working.

I hate intermittent problems :soapbox:

So replace the relay and see if the problem comes back. I am not a big fan of doing both at the same time because you're not saving any work and you'll never know which one fixed it. If its not the relay, it almost definitely will be next time.

I had 2 thermo switches go bad on me, my original and a new one that lasted a week or two. Neither was intermittent.