I jumped quickly to buy a set of gauges that were for sale locally on the FB Marketplace. The price was good, but they came without sending units (electric water temp and oil pressure gauges). I have been doing some online searching, and found out that Classic Motor Coaches used these in their repro Porsche Speedsters. CMC is long defunct, so I’m fishing for someone who might have some info on these gauges. Didn’t notice until I got them home, that the speedo is KPH. It uses the old square end cable. Apparently, this set was used in a T-bucket that I understand had an engine fire. I will need sending units, and some idea on how to wire them. I did take a picture of the only emblem I saw on the gauges. Any input would be appreciated.
I think even as reproductions they'll cool gauges. As an electronic technician I would check them individually since you know nothing about them. I have test equipment which makes it easy. Without would be harder but doable. The ammeter may need an external shunt. It looks like illumination is a wedge lamp, like #194? So I would start with a 12 volt battery and clip leads. Be sure they illuminate. Ground case...power to lamp. Ammeter...I would clip lead a light bulb in series, start low like a 194. So ammeter in series with load (lamp). If needle moves with a 194 bulb, it needs a shunt resistor. If light lights...needle doesn't move, try a larger load like a headlight bulb. Needle should move slightly, headlight lights, meter is ok. Now try heavier load, like a car turn headlights on (engine off)...disconnect a battery lead...then put ammeter in series. Headlights will come back and meter will show current draw. Oil pressure. Mechanical is easy. If it's electric you'll need the correct sending unit...just like the fuel gauge & water temp. A variable resistor. So the oil pressure or fuel level or temp. reading has to be correct (the resistance matches pressure, temp or level indication on meter). Good pictures of the backs will help. Sent from my Bell Candlestick
I did the same thing a few years back. I got a full set of new VDO gauges for$50 but by the time I bought all the sending units, I have over 200 bucks into them. Sending units aren't a bargain.
This thread from a Porsche forum might help: https://www.speedsterowners.com/topic/cmc-vintage-reproduction-gauge-manufacturer
Do you have a fairly accurate ohmmeter, and a good wirewound potentiometer that goes from zero to around 1000 ohms? You will need them to determine the ranges of the sending units for the oil, water, and fuel level gauges. Tell me you have them and I can tell you how to figure out the upper and lower resistances of the sending units. If you're in the Kansas City area bring them over and I'll show you. Here's a link to a few million different types of oil switch and pressure sending units and their values.... http://www.wellsve.com/showall_ds_oil.php There are similar charts for coolant temperature and fuel level sending units scattered across the internet.
51504bat, That was one of the sites I found in my search. Unfortunately, it doesn’t have any useful responses. Ebbsspeed, thanks for the useful link. I have a decent ohmmeter, but not the wire-wound pot. Guess I could try some known resistances in line and get some indication of the relative deflection on the scale. That should give mea decent ballpark.
Well, I’ve ordered a 1k-ohm wire wound pot. It will take it a while to arrive. From what I know about gauges like these, I presume I will crank the pot to max resistance, then hook 12V across the gauge and slowly lower resistance while watching needle deflection. By noting the point at which the gauge reads certain values, and measuring the pot’s resistance at that setting, I should be able to figure the right sender for each gauge. Did I get that right, Ebbsspeed?
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