View single post by Mason Jones

Posted: 01-07-2012 08:14 pm

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Mason Jones

Joined:	06-03-2011
Location:	Austin, Texas USA
Posts:	97
Status:	Offline

I have 2 Smiths Volt meters and neither of them work. The first reads 120 ohms when measured with a VOM which is normal but it blows the fuse when I turn on the ignition. The other reads infinity ohms so must have a broken wire inside. So I set out to take them apart and see how they work and if I could repair them. Hopefully the photos (bad as they are) will help someone else.

I started with the one that reads infinity. To remove the bezel you need to twist it until the 3 tabs line up with the slots. First pry the 3 tabs out a bit--just enough to loosen them so you can turn the bezel.

Next remove the slotted nuts and all the washers and insulators from the terminals on the back. It’s important to do this before you remove the face of the gauge because the needle is attached to the terminals via the mechanism inside. If you don’t remove the terminal nuts the needle will get bent when you pull the face off.

With the bezel and glass off you’ll see 1 tab that holds the face on. Bend it out. Then very carefully pry the face up. I bent the needle doing this part. (Note the importance of finding a clean workspace.)

Inside you’ll see the coil that heats the bimetal strip that moves the needle as current flows through it. The wires were not soldered to the terminals. They were attached with a green enamel and one had come loose. I sanded the bare end of the wire to remove any leftover enamel. I tried to solder the wire but the terminal was too heavy for my soldering iron and dissipated the heat too quickly.

I ended up using a short length of heat shrink tubing around the terminal to secure the wire. Worked great! It now reads 120 ohms across the terminals.

On to the one that blows the fuse. Further testing showed that the green wire terminal was grounded to the body of the gauge. I could have switched the wires I guess but I’d rather find out what the problem is. I removed the terminal nuts and sure enough, one of the terminals was coming in contact with the body. When you tighten the nuts it’s important to keep the terminals centered so this doesn’t happen.

While I had the bezels off I cleaned the glass and sanded/painted the bezels. I used a satin black spraypaint which seemed to match the other gauges well. Looks much better!

Tested both gauges in the car and they seem to work. There is a slot in the back for calibrating them but I’m not sure if I’ll bother to do that as they’re not that accurate anyway. If I get brave I may try to touch up the black on the faces.

Also, this post was extremely helpful in troubleshooting these and the other gauges:
http://www.jensenhealey.com/forums/view_topic.php?id=14&forum_id=7