rewiring 1973 - oil pressure light dim at instrument cluster

[BRBa]

Nearing completion of rewiring a 1973 Kubelwagen replica. The oil pressure light is considerably dimmer than the charge/generator light. The wiring was as shown previously with the warning lights outside the speedo and I chose to revert to "stock" (not Kubel stock). As can be seen, the old socket holes in the speedo have residue of caulking which was used to plug them for some reason. I thought I had cleaned that mess up sufficiently but evidently not 'cause at first I could get neither to light. I currently have a wire running from the fuzes to the center connector (same original wire on a double spade connector which jumps to the other light, seen atop my knee). At one point I got a large spark touching that wire to the oil pressure light bulb and must have burned out the bulb. But after some work, I got a test lamp to light up brightly on the wire to the generator light, and then that light to work in the speedo as it should, but cannot replicate the brightness with the oil pressure light. I checked continuity on both wires and it was good. The vehicle has been sitting a while as it undergoes the wiring project. The oil pressure switch is actually new from April 2022 when it replaced an old one which was leaking. Any thoughts appreciated. Maybe I fouled up the oil pressure switch when I burnt out the bulb? Thank you. (Yeah, the yellow and blue connector crimping/etc. on the new wiring is kinda homey...)

[ashman40]

The three indicator lamps at the bottom of the speedometer are separate from the rest. You can see that they sit inside a plastic housing that insulates them from the rest of the speedometer bulbs which ground thru the casing of the speedometer.

The three indicator lamp holders at the bottom of the speedometer don't know which of the three indicator lamp holes they are in. Functionally the three holes are the same. It looks like the center turn indicator hole was not caulked over. Try installing the oil lamp in its bulb holder into the center hole and test to see how bright it is. Compare this with the GEN lamp and the turn lamp for brightness when installed in the same hole. If the OIL lamp is noticeably dimmer than the rest swap the bulb+bulb holder out with any of the other illumination or indicator bulbs. Does this make a difference Try swapping just the bulb determines if the problem is with the bulb, the bulb holder or the wire. Use a new jumper wire to ground the OIL lamp bulb holder spade to a good ground at the dash. Does the bulb light up brightly? If it is bright with the jumper wire but dim with the blue/green wire, you know it is a problem with the wiring or the switch at the engine.

The oil pressure switch below the distributor is a simple ON/OFF switch that grounds the blue/green wire to the engine case when the pressure is less than around 5psi. With the engine OFF (0psi) the resistance thru the switch should be zero ohms. Test this at the switch with the wire disconnected. Test the resistance between the engine case and some part of the chassis, it should be zero ohms but 0.5ohms is ok. Next, ground one end of the blue/green wire and test the resistance to ground thru the wire to see if the wire adds more than 0.5 ohms or resistance. It should really be close to zero ohms. Try wire brushing the wire ends to improve (reduce) the resistance reading of the wire. If bad, clip off the terminals at the ends of the wire and install new crimp on terminals to a clean conductor under the wire insulation and retest.


Report back with your test results and test readings.
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AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[BRBa]

I put in a new oil pressure switch, CarQuest part number SBA1086 from an Advance Auto store in Virginia which had one in stock, and now the "idiot" lights work. I did clean out the sockets with a chainsaw sharpening stone chucked in a Dremel and got some shiny metal. There was an extra wire going from the dash to the back, to be used for the replica KW Notek blackout tail light, and it, the charge light wire, and the oil pressure wire all had the same continuity reading, so I guessed it was the switch, and got lucky. The oil pressure switch I replaced was installed in April '22, but it may have been one I had sitting around for a long time and not brand new. Thanks for the help. I also determined why neither warning light glowed on the face of the speedometer. There was electrical tape over the holes they should shine through.