Okay my girlfriend's father took his vette for some work and after picking the car up and getting it home a day or two later he noticed the cover and bulb were missing for his light. He swears it was working before and went back to the shop and the guy said he had removed it so it didn't kill the battery. They couldn't get the light to work and the mechanic had probed the wires behind the bumper and was telling him it had no voltage so when he had brought it to me I had unplugged the plug at the bumper and I was reading voltage so my only idea was he must have did something with the mechanism in the light itself. Well the new light came and I plugged it in before installing to test and it wasn't coming on and now what I had picked up on with my meter is when the light is off it is getting 12 volts but when the light activates the voltage goes away to almost nothing I don't remember the voltage exactly but I do know I took a couple LEDs I had on a strip in touch them to the terminals in the light housing and I can't open the housing back and forth and turn the LEDs on and off it is just losing so much voltage it can't power the halogen bulb. I did a little searching but hadn't seen any issue is he is having but I was telling him it seems more like a relay or body control module issue but it is also add that it worked until the guy removed the bulb and cover.any ideas? Thanks

 

Leaving the hood open will not cause the battery to go dead. The hood light will only stay on for a short time and then turn off. That is if the guy did not do something wrong to the car. I would confront the guy and make him fix what he messed up!

 

I hear you I was I hear you I was also telling him that it is on a timer that I don't know why the guy wouldn't know that when he is supposed to be one of the Corvette gurus around here. Seemed like the guy was kind of blowing him off and I am really good with electronics so I figured I would give him a hand but to me it seems like it is one of the issues mentioned but yet I haven't seen any posts like that

 

I won't take it back to the guy. That would be risking to make things worse and, if you're good with electricity, it's not worth it.

The symptoms you describe correspond to a bad contact. You have a point that is not completely open (otherwise you wouldn't be able to measure any voltage), but it has a high contact resistance.

The reason you get 12v with no load is because your multimeter doesn't load the circuit and therefore the voltage drop at the bad point is negligible. Once you load the circuit with the bulb, the current it drains is enough to produce a voltage drop of almost the whole 12v at the bad point.

You could begin troubleshooting this at the hood light connector that's below by the right side of the radiator. Clean the connector pins and directly connect the bulb there. If it doesn't work there either, check and clean its grounding point.

If it works, your problem is between that point and the hood lamp housing. Most likely dirty contacts at the connector mentioned above or bad contacts at the lamp housing (probably the result of being abused by the shop).

 

I get what you're saying about the wiring but anytime I have dealt with a bad or broken wire just moving around time to time would change the results and I would pick up on it but this he has been over two separate occasions the wires have been moved excetera and I can't even lose the 12 volts when it is unplugged the wiring from the light to the bumper look good I didn't find the connector at the firewall yet which I had seen mentioned. I may have to make a temporary harness of my own to test from those points or check resistance through each line itself

 

Not all bad contacts manifest themselves in the same way. The ones you mention now are the intermittent false contact kind. This one seems to be a constant connection with a high contact resistance: dirty ground points, dirty connectors, switches with internal contacts pitted and with heavy carbon deposits, bad solder joints, etc.


The connector is not by the firewall. It is upfront by the right side of the radiator, as I mentioned before. That should be your starting point to troubleshoot this because it will allow you to reduce your search area at once. Working from the hood lamp housing doesn't allow you to do that.

 

Got tied up yesterday...yes I've tested at hood connector w same result. Another post had mentioned that the next connection is near firewall I'd assume near battery but didn't get to look any further.heck I was hoping was a ground but it's definitely in the power line.hood plugs very clean and been unplugged about 6 times and probed right on pins so if contact there w as clean everything looks I'd think symptoms would at least briefly change as turn on once, read no power etc

 

If you directly connected the bulb to the hood lamp connector (C113), as I suggested, with the same results, then the problem is upstream the connector.

Before messing around with harnesses and fuseboxes, check and clean first Ground Point G102 - Splice Pack SP100 (Point 8 in diagram below) and repeat the test.

I've attached a schematic and a diagram showing the ground points locations to help you visualize things.

 

Just an update.... so I was telling him the last day I looked at it that's since it was powering the couple LEDs that I used as testers that maybe we could try an LED Hood light bulb and see if it powered it which he couldn't find locally so he ordered a few well he just messaged me and informed me that the LED bulb works fine in there so we are just going to leave it alone for now. Definitely doesn't seem like a connection issue because the LEDs always work when connected but the halogen bulbs don't

 

This my friend is telling you that broblem lies on connectors etc. There is too much resistance on circuit to feed current needed for light up halogen but enough for led. With halogen bulb attached, measure dcv over all joints one by one. Shoud be less than 0,2v on each.

 

That's what I've been saying all along since Post 4 above: