Boxerworks.com

I need some professional advice. I purchased an '84 R100, and it's running again. No big issues, just new battery and clean carbs. The speedo light was out, so I opened up the instrument assy to replace the bulb. I thought the oil pressure light was burnt out too, but it was not. Now I cannot seem to get the light to come on, it's always out.

When I turn the ignition on, the light does not come on. If I apply power to the proper pins on the back, the light will come on. When I check continuity from the brown/green wire on the switch up to the multi-pin connector on the back of the instruments, it's good. According to the wiring diagram, there is a green/blue wire that powers the Neutral, Charge Indicator and Oil Pressure light. However, the Neutral and Charge light work.

Anyone have any suggestions what I could check?

Thank you,
Steve

I would suggest the obvious answer is that either the sender is defective or the wiring to the sender is broken/disconnected. With everything assembled, pull the sender wire, switch on the ignition and ground the wire. If the lamp comes on then it will be the switch. A replacement switch will cure the issue. If not, the connecting wire is brown with a green tracer. It goes through the loom emerging near the rear frame downtube in a twin connector (the other wire, Brown with a black tracer, is the neutral switch wire). A sub-loom connects the two wires to their respective switches.

Rob

I will check that. Thank you,

Steve

I found the issue. It was a little bit of grunge inside the pressure switch. It was first checking good, with continuity. Then later I discovered it was reading open. So I flushed it out with some carb cleaner and removed a bit of gunk. Perhaps that was holding the switch open, which caused an inconsistent reading. Now that it's working properly, and after tracing all the wiring down, it seems to be operating correctly. Thanks for the advice.

Steve

Glad you found it...

Rob

if you have sludge in the sender, you might consider dropping the pan to clean it out as well

Always a good idea to drop the sump on a new to you bike that has been standing for some time - DAHIK!
A quick check can be done by removing a rocker box, as sludge can sit in the bottom of them too.
When you have the covers off you can also check oil flow to the rockers, sludge might have blocked them too.

DAHIK?

Don't Ask How I Know. Or as an alternative, Don't Ask Me How I Know (DAMHIK). Some go as far as to add IJN at the end...I Just Know!

Kurt

Luckily on the auto motor in question the big end shells, main and thrust bearings could be replaced without removing the motor, so not a major disaster.

I now allway follow the full sump off and flush the oil ways procedure to try and get everything out and refilled with new oil.
Valve guides and stems are important too, if the exhaust valve has been standing open there is a fair chance the stem will be rusted and the valve might be stuck and hit the piston first time round!