22 minutes ago, Captain Obvious said:

Yup. It would be cool to run that test again using an analog ammeter in series with the gauge. That way, you would be able to see a better representation of the PWM regulator current.

How about an oscilloscope for voltage readings at the resistor? I blew up my last analog ammeter many years ago. Even replacing the fuse in it didn't bring it back to life, and SWMBO would not be happy if I went out and got the Simpson meter I have wanted for a long time. (Maybe I could get away with it after she's been working for a while. Shh!)

Naaa. A trace on a scope just wouldn't have the same impact as watching the needle swing. I think seeing the needle swing with the current switching would give the best sense of what is going on. I think that would convey the concept the best.

I'm not sure I have an analog meter around here anymore either. I'll take a look, but I don't think so.

I found an inexpensive 600mA analog ammeter on Amazon. I should get it tomorrow. 

@Captain Obvious, you make it difficult to ignore these intellectual experiments. 

Haha!! Trust me... It'll be worth it. The video will help a lot of people understand what's going on.  

11 minutes ago, Captain Obvious said:

Haha!! Trust me... It'll be worth it. The video will help a lot of people understand what's going on.  

It's a tiny meter, about 1.5 inches by 1.5. The nice thing is that if I blow it up, it was cheap. 

That should be fine.  I got zoom on my screen.    

Last night I was driving and the gauges started working again - sort of.  They weren't consistent as they moved back and forth.  Do you think it still has something to do with the regulator and I have to pull the gauge?

 

 

If they are both moving all back and forth, I would think it would be the voltage regulator.

Here's straight from the FSM troubleshooting guide:

I pulled the gauge and I do have power from the dash harness. Since the issues resides at the gauge is there a way to fix the voltage regulator?  Or wire a new one into the circuit. Or do I need to replace the gauge?  

There are places that might be able to repair/replace the voltage regulator.

https://www.google.com/search?q=automotive+gauge+restoration&sxsrf=ALiCzsa7dCxxAJmczzDprB3YHBA44vbQSw%3A1663426703398&ei=j-AlY7jrF7-kqtsPhJys0Ag&oq=automotive+gauge+res&gs_lcp=Cgdnd3Mtd2l6EAEYADIFCAAQgAQyBggAEB4QFjIGCAAQHhAWMgYIABAeEBYyBggAEB4QFjIGCAAQHhAWMgYIABAeEBYyBQgAEIYDMgUIABCGAzIFCAAQhgM6DQgAEEcQ1gQQsAMQyQM6CggAEEcQ1gQQsAM6BAgAEEM6CAgAEIAEEMkDSgQIQRgASgQIRhgAUPoJWL8MYNUcaAJwAXgBgAHlAYgB0gOSAQUwLjIuMZgBAKABAcgBCMABAQ&sclient=gws-wiz

ebay offerings are probably cheaper. https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=280Z+temperature+gauge&_sacat=0

If you go the latter route, save your gauge. Someone may want it to have one to restore later.

Thanks Steve, I bought one on ebay.  I know nothing about how these work but I am extremely curious so I opened it up.  It seems pretty straight forward though. How can I tell which part failed? Is there a way to bench test it?

Like I said, I am just curious and love to see how things work. So it's all I can think about right now!  ha!