72 3.0 CS 2240344 Restoration

[ScottAndrews]

The dancing gauge can probably be remedied simply by placing a capacitor across the gauge terminals.

I'll ask Don how he dealt with the temp gauge. That is one very strange device. I am wondering if perhaps the one i have is inoperative. I cannot get it to register anything other than zero or full scale..and once it goes full scale, you have to drop the voltage down to about 1 volt to get it to come back to zero.

I just found VDO voltmeter that appears to be the right size. I also found a Porsche 911 gauge that has oil pressure onthe right hand side. It looks like the same basic gauge guts as the BMW one, only oil is onthe right hand side, so I can convert that to a volt meter, either swap the needle, or paint the Porsche one...

 

[ScottAndrews]

So yesterday I ordered a couple of other VDO gauges. I am hoping these can replace the wonky temp gauge I have been trying to retrofit into the spare fuel/temp gauge I bought, As noted above, the fuel gauge works fine, and I am pretty sure I can recalibrate it to work with a standard VDO oil pressure sender. The temp gauge seems to be inoperative. It reads zero up to about 3 volts applied, and then jumps instantly to full scale. On the way back down, it stays stuck on full scale until about 0.9 volts, where it instantly drops to zero. I can get the voltage scale to change using resistors, but it still has this jumpy binary characteristic and the hysteresis.

So I found a VDO voltage gauge from a BMW motorcycle that looks like it has the same sort of VDO meter movement (needs to be a lot side pivot zero down meter - otherwise I'd just use another gas gauge meter and turn it upside down.. But that would have zero at the top, which would look odd). . Here is the gauge.

The other one I got is a vintage Porsche 911 gauge that has fuel and oil pressure. This looks like pretty much the same type of meter used in our coupes, so I am hopeful that the oil pressure gauge may be usable as is, just drop it into the BMW housing (after changing the meter face using my sticker, and painting the needle off white). If that is the case, then I'll probably redo m y gauge stickers to swap the voltage and oil pressure right to left (Oil is currently on the left), and recalibrate my fuel gauge to read volts, which should be dead simple... This one is attractive as well because it uses the same meter attachment approach with a stud on the back side for each meter.

 

[e9Leveque]

The day you figure this out I see a run on those Porsche gauges on Ebay...

 

[mulberryworks]

The temp gauge seems to be inoperative. It reads zero up to about 3 volts applied, and then jumps instantly to full scale. On the way back down, it stays stuck on full scale until about 0.9 volts, where it instantly drops to zero. I can get the voltage scale to change using resistors, but it still has this jumpy binary characteristic and the hysteresis.

Many decades ago I was fooling around with some Detroit created gauges and was disappointed when I realized that the fuel gauge seemed to use a bi-metallic element and a heater coil rather than a wire coil and magnet. This explained why the gauge took a while to come up to full after filling my tank. Cheap and rugged I suppose, and it would prevent the rapid needle movement I'd seen in my VW beetle's gas gauge which is run by a simple mechanical cable run from the gas tank to the dash just over a foot away. I wonder if the temp gauge is a similar sort of type, to reduce fluctuations.

 

[ScottAndrews]

Many decades ago I was fooling around with some Detroit created gauges and was disappointed when I realized that the fuel gauge seemed to use a bi-metallic element and a heater coil rather than a wire coil and magnet. This explained why the gauge took a while to come up to full after filling my tank. Cheap and rugged I suppose, and it would prevent the rapid needle movement I'd seen in my VW beetle's gas gauge which is run by a simple mechanical cable run from the gas tank to the dash just over a foot away. I wonder if the temp gauge is a similar sort of type, to reduce fluctuations.

That's what I originally thought, but it is indeed a moving iron type meter movement (a fixed coil with a mega net attached to the needle.

My understanding, after a bit of sleuthing was that the temp gauge had a sort of dead band in the middle to avoid showing rapid swings in temperature, which might freak out the driver. However the meter I have seems to have the opposite behavior. It refuses to stay anywhere in the middle, bit instead resides at one end or the other, depending on a very tiny change in applied voltage. It is possible that I am somehow hooking it up incorrectly, and causing ti to work in the opposite way it was designed.

I suspect the dead band may be created by having some constant magnets inside the armature coil, and it is possible that by hooking it up wrong I am not powering those correctly, but I have tried all manner of ways and get the same behavior.

 

[ScottAndrews]

Took a trip to visit Don today to drop off the Gen 2 dash speaker baffles.

On my way home, I stopped off to see what was up with my car. They have made pretty good progress!

Driver side front floor is in. Passenger side rocker is in. Gaping speaker holes in the package tray are gone. The front passenger floor is removed and ready for replacement. And they have done various body panel flattening. There are a few dents on the right rear quarter that need tending to, and it looks like the rear driver's side passenger floor will also need to be replaced (after blasting it started showing some "lace").

He thinks it should be done in a couple of months...