My original ether-tube gauge broke and my spare ether-tube gauge appears to read extremely hot. This annoyed me- and while I do have another ether gauge, I did not want to install it until I'm finished monkeying with my engine (maybe never).

Paul Malloy and others have worked out an electric gauge, so I figured I try it with what I have here at the house. I don't have an old 240, but I did keep parts from my 86 740 GLE, when it went off for scrap.

Knowing that the temperature gauge from a 1986 740s fits right into a B18 head, I took apart the instrument cluster I saved from the same car.

The temp gauge comes out easily and after a little work to remove the face and needle, I was rewarded with a nice compact little gauge with three terminal. These were marked "+", "-" and "U" The U is upside down and I suspect it is the ground terminal.

I glued a 122 temp face to the 740 gauge - the screw holes do not quite line up perfectly, but since the mount is plastic, it can be easily re-drilled.

A nice thing is that unlike the picture of paul's sensor, with this one the needle sits exactly where the original one did. But one problem is that the 122 gauge needle sat on a much larger pin than the 740.

To temporarily get around this, I filled the needle with silicone and placed it on the smaller pin to cure. Seems to be secure, but it might need a better solution...

The tricky part is that the whole assembly is a little too tall. In fact, even if you drill out the original mounting plate, the complete gauge is about 1/8" too high and strikes the back of the clear instrument panel face.

I ran out of time this evening, but I think a simple flat square cover plate will give the gauge the "back" clearance needed to fit. I'll try and make a new plate tomorrow or Thursday. I think making a new plate is the hardest part of this entire conversion project.

Aside from already having the gauge and sensor, I chose the 740 because they are very common and very cheap here in the St. Louis junkyards. Plus it is a nice VDO setup with off-the-shelf replacement sensors.

So... I do not think this gauge needs a voltage stabilizer - it looks like it might have one right on the circuit board - please let me know if it does need a separate one...

To wire this up, I think I should attach the "+" to the fusebox, the "-" to the sensor and the "U" terminal to the panel ground (probably right to the plate)

Does anyone see any obvious problems?

If this works, could a 740 fuel gauge also be tried? (I suspect that the sender resistance values differ too much...) Still, it might be a nice help for the bouncy needle problem...