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The accursed overdrive! In a '92 940 Turbo

B

bmessina

Member
Joined
Nov 22, 2003
Location
Peoria, IL
Hello...

I've got a strange overdrive problem in my new 940(automatic trans). The overdrive off indicator(little arrow) will occasionally come on and off of it's own volition. Sometimes the light doesn't come on at all if I press the button. The overdrive will engage... sometimes. An example - I drove about 5 miles down the freeway to get the emissions test the other day and the overdrive didn't engage the whole way. It was a driveup testing facility so I didn't turn the car off the whole time while getting tested. Hopped back on the freeway and the overdrive engaged. I thought it might be related to if the car is warmed up or not, but I've driven the car around town until it's heated up, hopped on the freeway, and it still didn't engage.

I replaced the OD relay, but no change. I'm driving down to Portland(from Seattle area) on Wednesday for Thanksgiving, so I'm hoping I can get this sorted by then.

If this isn't something I can't get done by then - Are there any concerns about driving down there without the OD other than poor gas mileage?

Thanks!
 
Ok, upon further research into the problem, I see there's some wiring I need to inspect. Darn work this week, I get in before first light and leave after the sun sets, which makes it hard to check this stuff out. If it turns out to be the switch, would simply taking the switch out of the loop create an "always on" situation for the OD, so it would engage?

Thanks,
 
Removing the switch as you say might work, depending on where the actual fault lies. But then you might have better luck bypassing the relay, unplug it and then jumper pin #87 and #15 in the relay connector, ignore #87a. Note: dont expect the OD light to function at this point. This simple test should show where the problem lies.

From this point if the OD works reliably the the fault lies in the OD relay, or the OD switch and its wiring. If it continues to act up then the fault is either in the #15 wire which goes to a fuse, or the #87 which goes directly to the solenoid, or the solenoid it's self.

The described behavoir suggests that it is either the OD switch, the relay, or the #15 power supply, as the OD light is grounded by the relay when the relay is turned off or looses power. If the problem were in the #87 wire, or the solenoid it's self, the OD would act flakey but the OD light would remain off.

I hope you can make sense of what I just wrote. :wink:
 
Actually, I was able to decipher your ramblings, and I appreciate the privledge of doing so.

Are the pins clearly marked, or do I need a wiring diagram? If I do need a diagram, you wouldn't happen to know where I could find one to print out, do you?

I really hope it turns out to be a wire, or the switch, as it appears I can get that fixed before I leave. Now if I could just find some daylight.
 
Three Fat Tigers said:
Removing the switch as you say might work, depending on where the actual fault lies. But then you might have better luck bypassing the relay, unplug it and then jumper pin #87 and #15 in the relay connector, ignore #87a. Note: dont expect the OD light to function at this point. This simple test should show where the problem lies.
Click to expand...

I command this thread to RISE FROM THE GRAVE!

I having the same problems (have been since the beginning of winter now) with my O/D. I thought I had solved the problem last time by just going through and wrapping a rubber band around the little spring loaded plate in the relay. This caused the O/D to always stay on, but the arrow light would still flicker on and off on the dash and occassionally just stay on.

UNTIL TODAY.

now, the arrow light stays on constantly, and the OD doesn't engage. I have read some other posts that say I may want to check my tranny fuild level (it should be ok, me and owns6 changed it not 1.5 months ago).

My main question is this.. What gauge wire should I be using to jumper the connections? Is there major current going through those connections or should I be fine with some 'standard gauge' (not sure on the actual gauge) solid core wire?
 
and one more problem makes three!!! I am so glad I caught this thread, maybe you guys can help me out with my mom's problem too. She has a 91 940T and her overdrive works intermitintly. The light stays off unless the button is pressed, but sometimes the od just doesn't work. We replaced the Solenoid and the Relay (with new ones) trying to find out the problem, but no luck. Someone said something about a tranny rebuild, but that's quite a bit of cash for troubleshooting, especially when it could be a bad wire.
I don't understand how you guys are doing this jumper wire approach. The relay sits way behind the center dash, and I can barely get my fingers in there to plug in the thing. Do you take out the relay block somehow? I am a 240 guy, not a 940 guy... my knowledge is quite limited.
Thanks for the help <><
Kirk
 
The purpose of the jumper is to eliminate the relay and it's control button wiring as well as the in-gear switch as being a possible influence on the problem. The jumper installed correctly will send power directly to the solenoid's power wire which is the default mode of the system.

Now if you want you could go directly to the solenoid and run a new power wire to it, snake it up the tunnel and into the engine compartment and with a small in-line fuse, attatch directly to the battery, or... you could continue the wire up through the gap in the fender at the windshield and into the car through the door opening and plug into the cigarette lighter. I've done this myself on a M46 to get home from Indianapolis. This again will by pass everything, leave it like that for a while and if the OD continues to fail then the problem is in the trans, soleniod or trans grounding.

As you can see from the wiring diagram I posted there is only one wire going to the solenoid, where the solenoid is grounded through the transmission/engine. If you use some standard 18 gauge zip electrical cord for this you'd have two wires available, one for the above test the other you'd connect to the car's original solenoid wire at the trans and then inside the car to a test light that you could monitor and while driving and see if it ever flickers or fails to light which would of course indicate a fault in the wiring or relay or in-gear switch, or that you turned it off with the OD button. Which if you then did the relay socket jumper you could tell if it was the wiring out to the solenoid, provided your confident the power to the socket is reliable.

You have checked your trans fluid level right?
 
Well, one problem solved.. I finally just popped the relay out, and took a good look at it under brighter light.. Lo'and'behold, cracked solder joints at the bottom of the assembly where the plastic meets the board. A few minutes later, some reflowed solder, and my relay / OD system works perfectly again.

As for jumpering the connection ksgadbois, I have a 780 and it is fairly straightforward for me to pull the dash apart at that point. once that is open, its easy access :)

I am afraid I do not quite understand all of your problem though, are you saying that the car will sometimes either have O/D or no O/D for the whole time the car is turned on? or it will only sometimes shift up to the OD? My guess (if the car will only go into OD for certain trips) is that there is a bad wire going to the solinoid.
 
yeah, my exact problem is that the car sometime has, or doesn't have od for an entire trip. Every once in a while we'll be surprised and it will click in, but usually it just doesn't work.
Thanks for the help <><
Kirk
 
Hah, and my problem still isn't completely resolved. I have a solenoid(from owns6) waiting to be slapped in there, but I haven't had the time since I got back from vacation to replace it. Tomorrow night, hopefully.
 
if any of you decide you think it is the tranni got a 121k tranni from a 1991 940t asking $150 in Corvallis oregon and could meet in PDX on certain dates.. Anyway thought I would throw that out there, I also have all the relays and parts if you need any of that stuff.
Sean
 
Well, I managed to replace the solenoid last night, and it fixed my problem.

I still have to finish the job this weekend, though... the old solenoid is still hanging up there. Before anybody says anything - I live in an apartment, and get home 30 minutes before dark! I need liiiiiggghhhtt.
 
No, darnit. Forgot about that. What's FCP? I need to find the equivalent for that here in the great Northwest. I can do that when I get back in there to pull the old one... It's held up somewhere.
 
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