Actually, I'm a dealer / installer / wholesaler / etc.
That said, yup, sure did, I killed a few.
Been there, done that. And I will do it again!
Maybe you got lucky.
I say never test there because my customers think if testing Volts is OK, then testing amps is OK, and that is not OK.
Set the meter to 20VDC. In good sun. With the battery connected. Test the controller red to the battery + terminal. It should be almost 0. Test the (either) controller black to battery - terminal. It should be almost 0. If either tests over 0.2V, the wire or clamps or connection between the controller and battery terminal is bad.
(Maybe a bad solder connection. The wire coating/protector they use is hard to solder to. Use extra rosin flux or just let the solder drip off for a while. I prefere scraping the stuff off with a knife until I see copper, then I solder.)
With the battery connected, test the battery V and the solar V. If the battery V is under or about 13V, the difference between battery V and solar V should be less than 0.2V. If the solar V is 18 or 20V, check the battery clamps are not making contact.
Disconnect the battery. Touch the controller outputs (red and black) together for a second, then seperate them. Test the voltage between, it should be 0 or less than 1V. Sometimes it will read the solar volts because the controller is confused. Start over 3 or 4 times. Then let it sit a few minutes, touch the battery clamps together for 20 seconds and try again. You want to prove it DOES shut off.
If those are OK, it is probably good.
Next step, disconnect the panel, then connect the battery. Meter on 20Vdc. Test the yellow to black. It should be 0 or less than 1V. If it is about the same voltage as the battery, the controller is shot.
(do not use cutters to cut both yellow and black wires at the same time. Don't let them touch now either.)
A few things to keep in mind...
A 2A panel is kind of small for a car size battery, and it will take a few minutes for it to rise 0.1V even in decent sun.
A Morningstar controller will not charge a battery below 8V at least. Sometimes 9V. A well planed safety feature.
If the battery is below 9V, I would suggest charging it first with another charger to get it past 12.0V. Then see if the battery V rises. Then if it is not rising do the tests.
The type meter I figure you have has a fuse for lower amps. But not for high amps, meaning the 10 (or 20A) setting. It may say next to where the meter lead goes in only for high amps "10A (or 20A) Unfused".
Just in case the fuse is blown, you could try setting the meter to 10 or 20A DC and testing. Disconnect the red (+) battery clamp. Put the red meter lead to the red battery clamp. And the black meter lead to the battery positive (+).
The reading should be over 1A in decent sun. There should NOT be a (-) before the number. This is the direct reading if the battery tests under about 13.2V.
(I blow my share of meter fuses too!)
A more accurate test is to check frequency or duty cycle, if the battery is about full. That is an expensive meter. I don't think it is neccessary.
There are a half dozen ways to prove a $30 controller is shot or working without a $200 meter.
The SG-4 is a great controller. I see it outperform units costing over double. Just don't second guess it without a good reason!
Is this a US32 panel? What kind of battery?
Let us know how the testing goes. Maybe I can suggest what is next.
G-
