Rewiring OD switch
Thread Starter
Melting Slicks
Joined: Jul 2002
Posts: 2,072
Likes: 3
From: Walled Lake MI
Rewiring OD switch
How hard is it?? My OD button on my 4+3 works about once every 15 times you push it, the OD unit itself works just fine, its just that the switch doesnt work all the time...anyways I would like to wire it so it only comes on when I push hte button to turn it on? How do I do this?
Team Owner
Joined: Mar 2000
Posts: 83,383
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From: Boston, MA
Re: Rewiring OD switch (Storz)
Well.... sticking a new switch in to fix yours is relatively easy. Changing it to be manually controlles also isn't too bad. You have to run a 12v lead to one side of the switch and then the other side goes to a wire in the ECM connector that you pull out of the connector and is the O/D request line to the O/D relay.
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Re: Rewiring OD switch (Storz)
Yeah one of the wires in the ECM harnesses (there are 2 plugs on it) goes to the overdrive relay. When the ECM commands overdrive it puts 12v to this wire which activates the relay which activates the overdrive solenoid in the overdrive unit.
Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
Re: Rewiring OD switch (Storz)
Why not find out what is wrong with the switch? Usually the switch is broken as they are rather fragile and they aren't hard to replace. A rod actuated by the OD button has a fine thread and can be screwed up or down to allow the switch to be contacted . You might investigate adjustment of the rod and also look at the condition of the switch.
- 1986 Original Owner -
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From: North Yorkshire, England
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Re: Rewiring OD switch (scorp508)
Yeah one of the wires in the ECM harnesses (there are 2 plugs on it) goes to the overdrive relay. When the ECM commands overdrive it puts 12v to this wire which activates the relay which activates the overdrive solenoid in the overdrive unit.
What most folks do is use an '85 ON/OFF switch instead of the momentary contact (pulsed ground to ECM) switch that the '86 - '88 use. Now when you hit the switch it sends a constant ground to ECM pin C8, a light blue wire. You'll need to pull this out of the ECM connector along with pin A7, a tan/black wire. This is the wire the ECM would normally ground to energize the OD Relay. You then connect the light blue and the tan/black wires together. Now whenever the ignition is on and the switch is on the OD is on and when the switch is off the OD is off, no ECM control. I don't recommend this though. I would do as jfb suggests and repair yours to factory working order. I guess that's just the way I am, wanting things to work as designed. Most folks like the Auto Trans like effect of the OD kicking off and back on when in 4th on the highway going to pass. You'll lose this. I'd fix it.
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Re: Rewiring OD switch (Storz)
http://www.newark.com
86-88 swith: 61F753 : $11.01
I can't find the late 85 on/off part # right now.
86-88 swith: 61F753 : $11.01
I can't find the late 85 on/off part # right now.
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Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
Re: Rewiring OD switch (scorp508)
I believe the 85 OD switch is a push on, push off which is Newark stock number 61F752
First check if your switch has a tight mounting nut and if it is being actuated by the adjustable rod.
First check if your switch has a tight mounting nut and if it is being actuated by the adjustable rod.
Team Owner
Joined: May 2002
Posts: 24,337
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Re: Rewiring OD switch (Ray Quayle)
Yeah one of the wires in the ECM harnesses (there are 2 plugs on it) goes to the overdrive relay. When the ECM commands overdrive it puts 12v to this wire which activates the relay which activates the overdrive solenoid in the overdrive unit.
Actually "When the ECM commands overdrive it puts" a ground "to this wire which activates the relay which activates the overdrive solenoid in the overdrive unit."
Actually "When the ECM commands overdrive it puts" a ground "to this wire which activates the relay which activates the overdrive solenoid in the overdrive unit."
The relay functions by having 12 volts across it. This energizes the coil and closes the circuit between the outermost pins allowing 12v to the solenoid. Whether the ECM provides the ground side, or the 12V side, I don't recall.
Read here if you wanna find out more about how it works:
http://forums.corvetteforum.com/zerothread?id=590563
But, if you short the two outermost pins on the harness leading to the Overdrive relay, it will bypass the relay entirely, energize the solenoid, and activate the console light. Don't forget to turn it off when in reverse or at low speeds. The low pressure switch inside the unit will prevent it from operating anyways if the fluid pressure drops below 40 psi.
Looks like you'll end up getting the new switch though anyways....
[Modified by CentralCoaster, 1:03 PM 7/17/2003]
Thread Starter
Melting Slicks
Joined: Jul 2002
Posts: 2,072
Likes: 3
From: Walled Lake MI
Re: Rewiring OD switch (CentralCoaster)
Well I fixed it, I took it apart and found a couple things. One the switch works just fine, it was just that it wasnt mounted to the shifter so when you pushed the button it would just push the switch down with out actually clicking it, and two the little T rod thing was too far down into the top of the shifter so that there was not enough room for it to active the switch...long story short, it works like a champ now. Even tho the previous owner has the wrong switch in there, its a double click instead of a single click to turn the OD on or off. Thanks for those who helped :cheers:
