Thanks Pierce,

Hope you had a great Thanksgiving!

Looked through twice and didn't see your drawing attached, so if you have one and can post it that would be great; otherwise no big deal, I'm sure I can puzzle out which pins do what by studying the relay.

The relay seems weak, as it wants to default to OD OFF, and there's a spring that tends to pull it in that direction. In playing around with it before I jammed it ON, it would intermittently work (manually tripped the relay ON, button would turn it OFF, then sometimes back ON, but sometimes not).

It would be nice to be able to lock out the OD if I needed to (I've been thinking about installing a trailer hitch). I'm thinking a toggle switch that bypasses the relay and button completely, mounted on the dash somewhere. As long as it was rated high enough to handle the current, I would think I'd be OK.

Seems pretty straightforward, but do you have any thoughts?

 

i haven't scanned that page of my greenbook. but the circuit is really pretty simple, the only tricky part is that the indicator light is across the switch, so switch on turns the light off, and the relay has a toggle circuit in it, push on, push off. the output of the relay goes to the OD solenoid on the transmission.

I'd try to fix it rather than fake it... at least, I'd test the button circuit, and if thats whats wrong, find the right blue&brown wire, and maybe put a pushbutton on it in the console. if the button is OK, i'd probably get a new relay.

 

oh geez, I should scan it... k, done.

note the .... stuff is optional, so it works fine even if its not there.

 

Thanks for this info Pierce. I'm new here and this is my first post. Just recently bought an 88 240 dl and I really just assumed the tranny was a non overdrive unit till I lurked around and found all these models have overdrive in their automatics. Didn't notice a switch on my gearshifter because it didn't actually have one.
I too just want to leave it at overdrive on. But now that I look at your diagram the shifter switch is never really left on correct? That it just activates another switch from within the relay no?
I'm gonna try jumping the wires like you mentioned. Haven't been under my car as of yet.
Thank you again!

(edit) Staring at your diagram again what if we just bypassed the solenoid (8/1)....wait.
This is really confusing me.

Okay bottom line if we can get current going thru the relay then the overdrive is on yes?

 

Yes - for OD to work the solenoid needs power. It then retracts, allowing fluid to flow between two holes in the transmission.

 

our 87 240GL (and every other 240 with the AW70 automatic I've seen) has a small button on the left side of the shifter, right about where your thumb might land.

that schematic really shouldn't say "Overdrive ENGAGED" and "Overdrive DISENGAGED", rather, it should be 'Overdrive ENABLED" and "Overdrive DISABLED". light on, solenoid off disables the OD. light off and solenoid ON enables the OD, the transmission will shift into OD when it thinks its appropriate based on hydraulic pressure and the fact that its already in 3rd.

 

The button on mine is just missing and there's a hole there.
Okay so I'm broke today. The idea is that according to Chiltons to test this relay take it off the car then stick a hose on the opening. When you blow into the hose it shouldn't allow air until you attach the wire to the positive terminal on your battery and ground the relay itself. It should click then you can blow air down the hole with the tube you put in.
Now what if I remove this relay then just take it apart and remove whatever it is that keeps air from passing thru? Then when that's opened up just reinstall it. Should you then have overdrive? No more electronic switch. Should go in overdrive after 45 mph no?
I know the right way is to just get another relay and replace the switch on the gear shifter,look at the wiring and check your other relays.
But all this so you can control the air flow of the overdrive relay so you can turn your overdrive on and off.
But if you rig it so air (fluid actually) can always pass then you'll have your overdrive yes?
Is it okay for the tranny to have overdrive on even at speeds below 45 mph?

 

I think I'm gonna try this.
Or maybe even wait to get this:
The simpler the better is what I always say!

Automatic Over-Drive Solenoid Bypass Kit

 

what you're talking about re: air/fluid would apply to the SOLENOID on the transmission, NOT the relay under the dashboard.

the IPD bypass plate is the way to go if your solenoid is malfunctioning. or if the control circuitry is totally fritzed (repairing that switch on the shifter is a class A pain).

45? hah. I think our 240 will go into OD at about 30-35 if you're just coasting along.

 

I got sidetracked today so I didn't get to remove the solenoid (Yep the solenoid. Thanks pierce!)
But now I'm thinking what if I just remove the smaller O ring?
Reinstall and that should be almost as good as that bypass.
Maybe even grind it down a bit.
Or even just take a drill to the holes to open it up.
But I'm thinking just removing that smaller O ring should do the trick.

 

I believe I've heard you can drill a hole or cut a notch or something to disable the solenoid. dunno the specifics.

 

Just pull the relay and put a jumper wire (short wire with a male spade terminal on each end) in pin #15 to pin # 87 and the OD will always be on . I had to do this for a while way back when my OD relay blew. I always carry the jumper in case it happens again.

 

Ah but that's assuming your solenoid still works.

 

You'll find that out quickly when you put the jumper in.

 

I'm taking your advice jagtoes. It would be far easier just to hear a click than to get underneath and mod out the solenoid.
Sorry for asking for I should know this if I follow the wires but is the relay under the dash?

 

Scott I don't remember where this relay is for a 240 but if it is a 740 it is under the radio where you pull out the fuse panel. Maybe some can jump in and tell us where a 240 relay is. When you find it just pull the relay out and plug in the jumper. When you plug in the jumper the arrow light should go out and you may not hear a click. You would need to take it for a ride and see when it shifts into 4th that the rpms drop down like it is in OD.

 

For the 240's - unscrew the glove box and remove it. You will see the relay to the left, by the center vents/radio.

http://cleanflametrap.com/odwire/

 

Thanks bubba! My light has never ever been on from the two weeks I've owned this car but I'll check it out.

 

wait, if the OD light is *out*, then your OD should be working normally.
when everything is functioninig properly, the light is ON when the overdrive is DISABLED

 

This is why I'm sure something is screwy with the wiring.
At 60 mph my tach is reading 3500 to 4000 rpm so I'm pretty sure I'm not hitting overdrive.
Could also be the bulb is out too. Or someone had worked on it.
But it came from a second owner with no car knowledge and has always payed a mechanic for servicing but you can never know what has been done.
I only payed 600 for it but it's solid as can be. Original exhaust with original catalytic converter. Odometer stopped working at 244 thousand miles and yet it passed Colorado emissions with flying colors.
Changed the timing belt last week. It was easier than changing fan belts on most front wheel drive cars today. And it only took me an hour.
I've only owned this car two weeks and I love this thing!