Help an Idiot Use a Multimeter

panthro · 1 Apr 2020 at 17:42

I am reasonably competent with most things but electronics is beyond me. I've got a 40A circuit breaker in my car that I suspect is faulty and therefore the heating in the car is not working (Mk3 Supra). I bought a multimeter but have no idea how to check if this CB is faulty or not. Any help would be greatly appreciated!

VaderDSL · 1 Apr 2020 at 20:08

any use?

wesimmo · 1 Apr 2020 at 20:16

Check the manual and test for continuity across the terminals. It should look like a little speaker normally.

Then touch each probe to the terminals at the same time and you should hear a noise if the CB is letting current through.

Hawk Tuah · 1 Apr 2020 at 20:17

Bit different to mine - but the three main things you'll use are from left (clockwise from off).

1: Measure DC voltage.
2: Measure AC votage
3: Measure resistance + buzz if there's a connection.

#3 should be the one you're after to test you're getting a connection through the breaker. You can test by touching the probes together - should get a buzz.

panthro · 2 Apr 2020 at 08:26

Thanks guys, I set it to #3 to measure resistance. It buzzes when you connect it to each terminal on the CB, which means I guess current is getting through?

Django x2 · 2 Apr 2020 at 09:04

panthro said:
Thanks guys, I set it to #3 to measure resistance. It buzzes when you connect it to each terminal on the CB, which means I guess current is getting through?

Correct, or at least there is continuity.

wesimmo · 2 Apr 2020 at 09:09

If so, check your manual again and test the wire coming into the CB to see if that's getting current. If so, start checking upstream for faults.

If not you'll have to trace back and see where it's failing. I'd also look at switch wiring as another obvious point for failure. Especially if you can pop those out from the dash easily.