1993 240 wagon - this car's only consistencies have been it's inconsistencies! An old luxury car w/ terrible maintenance has me experiencing odd electrical stuff, etc. - I'm using it 95% city to prevent malfunctions from keeping me stranded!

Overdrive - when I bought the car 2 1/2 years ago, the light on the dash would come on and the button on the side of the shift (automatic) lever would work. After some months of experiencing no extra gear for the highway, I tried replacing the relay behind the glove box - an odd sizzle noise that wasn't scary, but certainly not normal. This past week, the dash light for the arrow has reappeared, and as far as I know, there are 2 possibilities - try another relay, though the other was new from IPD or test/replace the solenoid on the transmission which I heard could even be w/ an aftermarket part. I assume that disconnecting the relay which just mean that I never get it into a higher, "relaxed" gear - it's prob operating that way now.

Know this - my funds are minimal and this car defies logic - from reading some other posts on the subject, sounds like the worst is that highway gas mileage will suffer, and keeping it 65 or below is prob wise to put less strain on the engine/trans.

Any ideas would be great - thanks in advance.

SPEND $40 AT IPD FOR THE 'PLATE'........

SLAP IT IN, TAKES AN HOUR IF YOU TAKE YOUR TIME.....

ENJOY TROUBLE-FREE OD BEHAVIOR FROM THEN ON.........

ONE OF THE BEST $40 I EVER SPENT........
--CARLOS

The relay requires a momentary application of 12v to set it. This is supposed to happen when the switch on the shifter is pushed in and released.

I assume you have cleaned the fuse panel and the fuse for the overdrive is good. Go to the relay and unplug it. Using a test light connected to ground probe each female connector on the plug until you locate the one that will cause the test light to illuminate while it is held in and go dark when you release it. Once you have verified that you can rule out a problem with the switch or it wiring. Likewise if you can not find 12v on the connector with the switch pushed in you have found your problem.

When the relay is plugged into the connector you should hear it clicking as you push and release the shifter switch. The overdrive light should be going on and off as the relay sets and releases. That function of the relay is supposed to supply 12v to the overdrive solenoid on the transmission.

If the momentary 12v is there and the relay is not responding by clicking and turning the arrow on the dash on/off I would remove the cover on the relay and use a strong light and a magnifying glass to look for a bad solder joint. Better yet resolder all of the joints on the board put it back in and try it again. If soldering is not a familiar activity for you perhaps you have a friend who has experience. It is not rocket science but like the medical profession policy- it is good to watch one, then do one, and then teach one.....

Randy

I'm assuming your car has an automatic transmission. My 740 wagon has the same symptoms, and I replaced the solenoid with the bypass plate from IPD. Instantly had overdrive, which kicks in at 38-45 mph, depending on throttle load. Others on the board have tried cutting a groove in the solenoid, and removing one (inner) o-ring,with similar results. Both procedures are outlined in the 700/900 FAQ.

Hope this helps,

Harry

1989 745, 192K mi

I had a problem of overdrive disengaging all by itself. Sometimes it would reset with the button, sometimes not. Read a little here on the board and concluded it was a bad relay. Opened up the relay and found several bad solder joints. Resoldered the relay and have had no problems since. Been about 3 years.

Charles
Houston, TX

Do you hear the relay clicking when you push the button? Are you blowing fuses?
Dan