Hi All,
Well here’s the issue. Day 1. A week ago my reliable automatic 240DL (180,000 miles), upon startup, activated the overdrive switch which I could not shut off and it stayed in 3rd gear for miles on an LA Freeway. Simultaneously, this also caused the power windows and radio to cease working. Exited freeway and drove home and shut off car and left it sit for a week, pondering vehicle retirement...Day 2. Yesterday I started the car and there was the yellow “up arrow” indicator for overdrive which, amazingly, I was able to shut off on the shift ****. HOWEVER...all functions and lights on the dashboard console (speedometer, gauges, indicators..etc did not work). The windows and radio did work. The car sounded perfect as it usually does.
I hope it is as simple as the bypass plate on the overdrive selector or similar, or a minor under hood component issue and not the kiss of death wiring harness. (I burned up a 1988 240 when the wiring insulation somewhere deteriorated, hot wires touched and...parted it out and towed to graveyard.
I love this “work truck”!! At least another 100,000 in that engine.
Thanks for all your upcoming suggestions

 

I'd check for poor connections in the fusebox, and for the overdrive a bad relay or insulation missing from wires can cause that. Cheapest solution is to bypass the solenoid and remove the relay to keep the light from coming on.

 

Thanks. I hear there is a plate to attach somewhere near the glove box to over ride overdrive. Started car yesterday and everything was normal, all indicators on dash worked and all powered accessories worked as well. Curious issue. too much life in engine to send to scrap I think

 

Cheapest and best is to change the O/D relay, that's most likely your problem.

 

The overdrive relay is mounted to the left of the glove box - you remove the glove box to get to it.

The plate you are referring to can be put in place of the overdrive solenoid on the side of the transmission. What the solenoid does is allow oil to flow to the 4th gear circuit in the valve body. You can simply modify the solenoid (for free) by using a dremel tool to grind a passage in the face of the solenoid to allow oil to flow - you will loose the ability to manually downshift to third, which very few do anyway.

 

I will buy that plate. The last few times I started the car, I had no dash gauges functioning. Only the up arrow indicator light for overdrive was lit. No speedometer, fuel gauges, odometer...etc. Still had functioning power windows, radio and door locks. I was able to switch off the overdrive on shift **** and the car ran well through all 4 gears.

 

The "plate" has nothing to do with your dash malfunctioning. The overdrive plates purpose is to permanently allow oil to flow to the 4th gear oil circuits and engage 4th gear when needed. It replaces your overdrive solenoid on the transmission. As said, you can do the same thing for free with a dremel tool on your existing overdrive solenoid. Sounds as though the relay may be going bad and getting stuck in the off position. Common problem with those.

I would suggest a bad electrical connection is causing the cluster to malfunction. First place to look would be the fusebox - those old ceramic fuse can get corroded on the ends.

 

I will try the dremel method to bypass overdrive. Will explore cluster issue after that.

 

Just be careful to not grind outside of the outer ring area, that oring still needs to seal.