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Old 05-08-2011, 11:48 PM   #10
VetteVet
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Join Date: Jan 2005
Location: Kalamazoo, Michigan
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Re: Brake warning light help.

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Quote:
Originally Posted by derotoreut View Post
OK here's the latest on my brake light and temp light. I finished my carb overhaul this weekend and now able to start the truck. I found out that the brake warning light and temp light DO NOT come on when ignition is in Start position. Do you have the ignition switch mounted so that it is grounded to the frame and back to the battery negative

Both lights tested fine as mentioned before. I did not use my multimeter to check the resistance across each of these wires back to the ignition switch because I got everything done this weekend and was able to actually start the truck. I thought for sure these lights would come on when cranking. Maybe the guy at Painless is right, that this harness really is not wired that way. You have got to check the continuity between the key switch body and the terminals where the brake light and the temp light connect to the key switch when the key is turned to start. Otherwise you won't know if the two lights are grounding. It wouldn't make any sense to run the wires to the key and then to the console if the key switch wasn't supposed to ground the wires. They would have run them directly to the console.

Another thing I noticed was that with both the temp wires (gauge wire and light wire) connected to the sender, the temp light will come on as the truck warms up. I watched the temp light and it would slowly start to light up and would be dim. The more the truck warmed up, the brighter that light got until the temperature reached the normal operating temperature. Once warmed up the temp light is on full bright. That is exactly how the sender would work. It is a variable resistance to ground. IOW as the engine warms up the resistance to ground to complete the circuit for the light or gauge, gets less and less and the light comes on dim and the needle on the gauge moves toward hot. Now here is the problem, you need a different sender for the gauge than you do for the light. The light sender has a lot more resistance than the gauge sender and won't let the light begin to come on until the engine temp gets up to the critical range and then full on at the overheat temperature. We're talking two different senders here. My question is just like Longhorn Man said " if you have a gauge dash why do you have a temp light?". You can have both but you have to have two senders and the pins in the console plug have to be rewired.

I know these lights work, but they just don't come on when cranking. Any more suggestions?
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