OD problem...scorp508 help?
Thread Starter
Drifting
Joined: Feb 2003
Posts: 1,978
Likes: 2
From: San Antonio Texas
OD problem...scorp508 help?
My OD ('86 4+3) isn't kicking in without pushing the button a bunch of times. Kicks out with no problem though. I've changed fluid & filter. I want to change switch & relay too. Does anyone know where the relay is located, and what color wires I'm looking for? Any help appreciated. Thanks.
:chevy
:chevy
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Re: OD problem...scorp508 help? (Curveit)
So the computer isn't turning it on properly? Have you noticed if it seems to come around the same temperature or not when it does finally come on? Your 86 should not have OD available until 122* (F) coolant temp.
Thread Starter
Drifting
Joined: Feb 2003
Posts: 1,978
Likes: 2
From: San Antonio Texas
Re: OD problem...scorp508 help? (Curveit)
The computer is no longer turning it on properly either. Normally comes on at about 122 degrees, now it comes on when it feels like it. It's kicked out a few times on the highway when I'm doing about 60-70MPH. That gets your attention. I found in search your question about wire color codes for the relay. Are these correct?
:chevy
:chevy
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Re: OD problem...scorp508 help? (Curveit)
The relay is between the brake booster and the intake.. on the firewall. well, there's two there actually. The o/d relay is in front, the fuel pump relay is against the firewall. They're the same part number.
Is your dash "overdrive" indicator light coming on in unison with the switch, or in unison with when the o/d actually feels lilke engaging?
If it comes on with the switch, then your ecm is trying to turn it on, and the relay prolly works, and I'd be looking for a loose connection (between the relay and theh overdrive solenoid), low fluid level, a sticky solenoid, improperly sealed filter/grommet, or some other thing to cause the internal atf pressure switch to open.
If the light only comes on when it actually engages, i'd suspect a bad connector in the shifter switch, a bad first gear switch (or whatever switches your year had on the 4-speed), a bad relay, or something else preventing the ecm from sending a signal, such as a bad coolant temp sensor.
I don't think the ecm uses the same temp sensor as the one that sends the signal to the guage display. I believe the car actually has three temp sensors, god know why..
:rolleyes:
[Modified by CentralCoaster, 1:17 AM 8/26/2003]
Is your dash "overdrive" indicator light coming on in unison with the switch, or in unison with when the o/d actually feels lilke engaging?
If it comes on with the switch, then your ecm is trying to turn it on, and the relay prolly works, and I'd be looking for a loose connection (between the relay and theh overdrive solenoid), low fluid level, a sticky solenoid, improperly sealed filter/grommet, or some other thing to cause the internal atf pressure switch to open.
If the light only comes on when it actually engages, i'd suspect a bad connector in the shifter switch, a bad first gear switch (or whatever switches your year had on the 4-speed), a bad relay, or something else preventing the ecm from sending a signal, such as a bad coolant temp sensor.
I don't think the ecm uses the same temp sensor as the one that sends the signal to the guage display. I believe the car actually has three temp sensors, god know why..
:rolleyes:
[Modified by CentralCoaster, 1:17 AM 8/26/2003]
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Re: OD problem...scorp508 help? (Curveit)
Curveit, read this post also....
It contains my whole discovery process when diagnosing o/d failure on my 85. I went nuts with rewiring and pulling the o/d valve body apart, but my problem turned out to be a torn filter grommet. .79 cent fix! :hurray:
http://forums.corvetteforum.com/zerothread?id=590563
[Modified by CentralCoaster, 1:21 AM 8/26/2003]
It contains my whole discovery process when diagnosing o/d failure on my 85. I went nuts with rewiring and pulling the o/d valve body apart, but my problem turned out to be a torn filter grommet. .79 cent fix! :hurray:
http://forums.corvetteforum.com/zerothread?id=590563
[Modified by CentralCoaster, 1:21 AM 8/26/2003]
Thread Starter
Drifting
Joined: Feb 2003
Posts: 1,978
Likes: 2
From: San Antonio Texas
Re: OD problem...scorp508 help? (Curveit)
Thanks for your info. The light comes on when the unit engages, so hopefully It's something minor. As I said, I'm going to replace the switch and relay anyhow. I've been waiting for something to go wrong with the OD for years, so I'm not really surprised at this. Again, thanks to you all for your help, and any other suggestions are much appreciated.
:chevy
:chevy
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Re: OD problem...scorp508 help? (Curveit)
When you inspect your relay check out the wires themselves. Mine had pulled out of the harness at one point causing a short circuit. I swear GM used about 1 millimeter more wire than they had to and the test of time pulled the wires out of their insulation some. I would hit a bump and OD would kick on/off/on/off. It was a pain. I had to clean up the wires and reseat them.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Le Mans Master
Joined: Jul 2001
Posts: 6,252
Likes: 2
From: Silicon Valley Kalifornia
Re: OD problem...scorp508 help? (Curveit)
:yesnod: Mine are the same. You can see bare wires at the connector.
:chevy
:chevy
Thread Starter
Drifting
Joined: Feb 2003
Posts: 1,978
Likes: 2
From: San Antonio Texas
Re: OD problem...scorp508 help? (Curveit)
:thumbs: With help from y'all, located relay, replaced relay; now all is right with OD once again. I was sweating that one; had visions of OD rebuild$$$$$
Thanks. Once again the forum comes through.
:chevy
Thanks. Once again the forum comes through.
:chevy
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Re: OD problem...scorp508 help? (scorp508)
I swear GM used about 1 millimeter more wire than they had to and the test of time pulled the wires out of their insulation some.
:withstupid: I noticed the same thing on mine. The bare wire was exposed, and two of the wires were crossed. This wasn't my problem, but I found it nonetheless, and saved a headache down the road.
