Will not engage overdrive clutch

Hi and thanks for using 2CarPros.

The first thing I would suggest is to check the overdrive relay. It is located near the heater box. I attached a picture of it for you.

Remove it and confirm no corrosion is causing issues. Also, here is a link that shows how to check a relay:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

If there is no power to the relay, check fuse 3 in the fuse box. See picture 2.

Let me know what you find.

Take care,
Joe

No relay found in the location your image shows. Your answer does help if I can track down the location of the relay for the overdrive solenoid.

Thanks

Are you certain? That is the only place I ever saw them. I checked two different manuals and they both show the same. Do you still have the owner's manual?

Joe,

I have the Full-Service Manual (FSM) from mitsubishilinks.com. Their sketches show the relay somewhere in that vicinity. However, I even studied the wiring diagrams and noted the wire colors and striping. It shows that there should be five wires going to the relay and the colors etc. I took out the passenger seat and glove box so I had visibility into that area. I just don't find a part matching that description in that location. I also looked at the driver's side, There is always the chance that the wiring diagram is wrong. I did find one relay with some wires matching those colors but with a green wire where to diagram shows red. So I'm stumped.

Thanks,
Tom

What color wires are going to that relay? I'll try to identify it via the wiring schematics I have. I wonder if someone modified something because like you, at this point I don't know where else it may be.

Let me know and hang in there. We'll get it figured out.

By the way, the picture I attached is the same on two different manuals and when I look up component locations, this is what I get:

Overdrive Relay: Under RH Side Of Dash Panel

I attached one of the schematics I have. Is it the same as yours?

Let me know.

Joe

Joe,

I'm going to provide some pictures of what I see in the location suggested. The fourth picture was taken from under the dash looking up into the corner at the finder inside panel.

The car has only had two owners. The original owner had all maintenance done by Pros. On the other hand, have owned the truck for the last ten years and have made minimal mods. The only electrical mod I have made is to run a hot wire directly to the starter solenoid from the battery through a push button switch. This was done because randomly the factory starting circuit does not provide sufficient current to activate the starter solenoid (i.e. a work-around to get sufficient power to the starter solenoid), It has gotten me going many times when the weak standard circuit fails.

Thanks for you help,
Tom

In the first picture, what is the black box?

According to my research using the P/N MD723747, the black box is a Free Wheel Hub Indicator.

I finally found the bugger after removing the computer and dropping the heater fan and plenum. Says Overdrive Relay right on the part (black box way in the back side wall). I don't give up easily. :'-) My windshield leaked in this corner, so I'm not surprised that the electronics got impacted.

Thanks for your help.

Glad you found it. It's crazy how things get buried. Anything to make the job easier. LOL Did you check it or replace it?

I'd like to check it. The fastener holding it in place is frozen, so I may have to drill out the head. I admit that I'm only used to checking relays with 4 terminals, not 5. This relay is no longer in production BTW. So if it is the culprit, I may be out of luck, unless I can wrangle a used one.

Do you guys know if the overdrive solenoid is energized continuously to hold the transmission overdrive clutch engaged or does it just take a short burst of 12 volts to engage with the solenoid? I may want to install a switch to engage the overdrive until I find the issue and solution.

I guess a better way to ask the above question is "does the the magnetic coil within the relay stay energized keeping the 12 volts output to the solenoid power energized the whole time the transmission is to be in overdrive"?

Welcome back:

That's a good question. Because of its age, I can't remember with 100% certainty. However, if the power is taken away from the coil, the armature will drop away and the power to the overdrive would be lost. Based on that, I am thinking it has to be powered the entire time.

Thanks for your help! Just as a follow-up I provide the following:

I studied the wiring and tried a jumper from the hot 12 volts source to the output wire on the connector at the relay to the solenoid. I could not get the power down to the solenoid that way. However, I ran a new wire from the 12 volts source at the relay and I got the overdrive working, yeah! The only issue I noticed is that the overdrive "off" switch on the shifter no longer works. Effectively I by-passed the need for the relay. It works for now. If I can ever find a source for the relay, I can put it back to factory configuration.

My trial attempt using the jumper without success makes me suspicious though. The issue may be in the original wire harness between the relay and the solenoid.

Tom

Hi, Tom. I'm glad you got it working. It sounds like you need to located the power supply to the switch and repair it. Can you just run a new power to the overdrive off switch to make it work? I attached the schematic of the system. I may have sent it already, but figured I would send it just in case.

Take care and let us know if you have questions in the future.

Joe