C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Doug Nash 4+3

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Old Sep 26, 2007 | 12:42 AM
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Driving my 85 down the freeway for 5 miles at 60mph, temp 181, out of the blue the OD turns off and a few seconds later turns on again. A mile later it did the same thing. After that it was fine the rest of the evening.

The switch is good, I can't help but think it has to do with the abnormally cold day today.

Any ideas?

Thanks.
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Old Sep 26, 2007 | 03:01 AM
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Check connections at O/d relay.
Early type relay connectors go bad regularly ; can lose connection or short out
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Old Sep 26, 2007 | 04:45 AM
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Did the dash indicator light stay on during this or go off with the trans?
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Old Sep 26, 2007 | 01:21 PM
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Originally Posted by CentralCoaster
Did the dash indicator light stay on during this or go off with the trans?
OD lite turned off also. Does that mean something in particular?
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Old Sep 27, 2007 | 11:12 AM
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Yes it means either the computer is shutting it off or the relay is shorting out or losing power. The wiring downstream of the relay and the whole trans is working fine however.

Check the wires at the relay on the firewall for heat damage.

Otherwise it could be a bad console switch or connections, an ECM coolant temp sensor reading below 140F, or a bad 1st or 3rd gear switch, or a bad relay.

The relay is the same p/n as the fuel pump relay behind it if you want to try swapping them.
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Old Sep 27, 2007 | 12:26 PM
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Originally Posted by CentralCoaster
Yes it means either the computer is shutting it off or the relay is shorting out or losing power. The wiring downstream of the relay and the whole trans is working fine however.

Check the wires at the relay on the firewall for heat damage.

Otherwise it could be a bad console switch or connections, an ECM coolant temp sensor reading below 140F, or a bad 1st or 3rd gear switch, or a bad relay.

The relay is the same p/n as the fuel pump relay behind it if you want to try swapping them.
That is very good information. I'll get right on it.

Thank you
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Old Sep 28, 2007 | 12:07 AM
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I had a bad connection on my switch. resoldered it and it's fine.
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Old Sep 29, 2007 | 12:42 AM
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Originally Posted by CentralCoaster
Yes it means either the computer is shutting it off or the relay is shorting out or losing power. The wiring downstream of the relay and the whole trans is working fine however.

Check the wires at the relay on the firewall for heat damage.

Otherwise it could be a bad console switch or connections, an ECM coolant temp sensor reading below 140F, or a bad 1st or 3rd gear switch, or a bad relay.

The relay is the same p/n as the fuel pump relay behind it if you want to try swapping them.
2 questions please. There's a relay near the cruise servo and another one near the wiper motor. Which one is for the OD. Also I need to clean those connectors out. Which is the best method for doing this (ie, alcohol/pressurized air, toothbrush, etc).

Thanks again!
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Old Oct 1, 2007 | 05:49 PM
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Originally Posted by The Beep
2 questions please. There's a relay near the cruise servo and another one near the wiper motor. Which one is for the OD. Also I need to clean those connectors out. Which is the best method for doing this (ie, alcohol/pressurized air, toothbrush, etc).

Thanks again!
There should be two identical relays by the wiper motor. The front one is the overdrive. Rear is the fuel pump. If your car differs from this, someone messed with it.

That goop in the connector is there to prevent corrosion. If you insist on cleaning it out, replace it with the same.

The major problem with these connectors is the insulation shrinking and causing shorts. I was able to slip 1/4" shrink tubing over the connectors to reinsulate each wire.
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