85 300D glow plug relay intermittent no glow plug light

[funola]

This has been an intermittent problem since I bought the car 2 years ago. I estimate it happens less than 1 percent of the time. I have cleaned all the terminals on the glow plug relay and have added test light bulbs across the glow plugs and the violet wire so I can see at a glance whether they are getting power.

Today, it happened again. No cluster glow plug light and neither test light bulbs were lit with the key turned to the on position, which means the glow relay was not getting the trigger signal and thus no glow plug light.

I recycled the ign switch about 20 times which didn't help. I then cranked the starter for a second, recycled the ign switch to on and immediately got the glow light and both test light bulbs lit. Note: I did not touch the gear selector throughout this ordeal.

The problem is in the ign switch apparently. Is there an adjustment in the ign switch? Maybe if I get ambitious, I'll take apart the ign switch and give it a good cleaning.