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Okay so the under hood-lamp on my c5 was working fine.
I tried to replace it with an LED bulb.
The connection was funky and LED bulb lit, but dimly.
When I wiggled the LED bulb with a dental pick, it would light brightly!
But in the process of wiggling the bulb around to find a good connection, I heard a pop (just like when a fuse blows).
After the popping noise, neither the LED or the factory bulb would work. No light at all.
Checked fuses, all good.
Glovebox and RV mirror lights still work fine (they are LED as well).
I was getting 0 volts at the hood lamp.
This may have been a BAD idea, but I gutted the housing and removed the factory mercury switch.
Hardwired an LED strip into the factory housing and added a manual shut off switch.
Essentially, the factory light is completely by-passed and the first 4 feet of wire are brand new.
I now get 5 volts and the LED strip dimly lights. So I am assuming the problem lies deeper.
I am completely at a loss for why I'm only receiving 5 volts.
I'm pretty sure the problem stems from the 'fuse popping' noise I heard initially.
Any help is greatly appreciated!
Sorry for the long read.
Thank you all!
-Jeff
When I bought my C5, the previous owner had removed the underhood lens and light bulb and put them in the console. I am guessing that he thought that may have been the cause of a battery drain or something.
Not sure what the 'pop' was in your situation. However, I have tried several different LED lights in the underhood light. None of the aftermarket LEDs fit tight enough even after modifying the contacts and the only one that impressed me with brightness was the RF light. I also ended up putting in the aftermarket switch harness because I don't trust the OEM switch to turn off due to the previous owner's solution. After I open the hood and put my manual switch on, I still have to tap the light housing a few times to get it to come on due to the poor fit.
When I bought my C5, the previous owner had removed the underhood lens and light bulb and put them in the console. I am guessing that he thought that may have been the cause of a battery drain or something.
Not sure what the 'pop' was in your situation. However, I have tried several different LED lights in the underhood light. None of the aftermarket LEDs fit tight enough even after modifying the contacts and the only one that impressed me with brightness was the RF light. I also ended up putting in the aftermarket switch harness because I don't trust the OEM switch to turn off due to the previous owner's solution. After I open the hood and put my manual switch on, I still have to tap the light housing a few times to get it to come on due to the poor fit.
This is exactly why I gutted the housing and hardwired in a strip of LEDs and a manual switch, instead of the factory Festoon bulb connections and Mercury switch that i was never fond of anyway. I Tried every aftermarket LED, even the twist loops.
One LED that did light bright was from Vettelights.com. But that was the LED that was dim until I wiggled the bulb. I ultimately grounded or shorted it out, causing this problem I have currently.
I have no idea what the pop was either. Sounded just like a fuse.
Could I have blown or burn a wire? causing Less voltage to run to the hood lamp.
The Fuse was the correct amperage but maybe the 21 year old power wire finally went?
I'll find the factory ground for this circuit and give it a good cleaning. Although I doubt it's the ground because all other lamps work as they should.
I'll follow the power wire as far as I can, but I'm in a tight garage.
Worst case scenario, I can probably tap into another constant 12v source and add an inline fuse before routing the new power wire to the hood lamp. I hope. Haha
Been through this.. Dim LED hood light. 98 convertable. When I would open the glove box door,, the hood light would go out. WTF...Fuse must be good,, I had 8 volts at the hood.. and 8 volts at the glove box..WTF?? ..LED's will work on 8 volts,,,,somewhat. Long story short,, it was the #2 fuse in the passenger footwell... Replaced the fuse and had 12 volts everywhere. Took out the hood light and threw it away. Dont need a hood light. Your vanity lights are also on that circuit. Nicknamed my car.."Superfreak"..Change that fuse.
If you are only getting 5 volts on the feed wire and the fuse is good it sounds like a partial short to ground to me...remove the fuse and the bulb and do a short to ground check with the ohmeter function of your multimeter !!...if you’re unsure how to do it give a shout !!
Are you trying the other bulbs since this happened? Did you test the same bulb with a battery after you heard the 'pop'?
Yes I have multiple different brand LEDs and the factory bulb. All stopped working once I heard the 'fuse pop' noise.
Originally Posted by Josephu
Been through this.. Dim LED hood light. 98 convertable. When I would open the glove box door,, the hood light would go out. WTF...Fuse must be good,, I had 8 volts at the hood.. and 8 volts at the glove box..WTF?? ..LED's will work on 8 volts,,,,somewhat. Long story short,, it was the #2 fuse in the passenger footwell... Replaced the fuse and had 12 volts everywhere. Took out the hood light and threw it away. Dont need a hood light. Your vanity lights are also on that circuit. Nicknamed my car.."Superfreak"..Change that fuse.
haha that is strange. All my lights worked fine though until I probed around in the housing and shorted something I believe. Passenger footwell fuse # 2 was the first thing I checked after it happened. It looked fine but I replaced it anyway. All other lights on that fuse still work fine (glovebox and RV mirror lights)
Originally Posted by Vetteman Jack
Moved to C5 Tech.
Thanks
Originally Posted by C5 Diag
If you are only getting 5 volts on the feed wire and the fuse is good it sounds like a partial short to ground to me...remove the fuse and the bulb and do a short to ground check with the ohmeter function of your multimeter !!...if you’re unsure how to do it give a shout !!
Fuse is good. Just got done cleaning the factory ground for the hood light. I believe it is the one near the headlight and coolant overflow. Cleaned it real good. No luck. Still 5v.
Just to check, I ran a new ground wire directly to the existing factory ground (same factory ground that I just cleaned). Didn't help or hurt. Still 5 volts.
Could this be some kind of problem with the PCM not reading enough resistance, therefore not allowing full voltage to the hood lamp? All lights in the circuit are LED and not drawing enough power? (Hood lamp, glove box, and RV mirror lights)
I guess my next step is to find a 12v CONSTANT? wire and tap into that and see if I get my 12 volts. I will be utterly stumped if that doesn't work...
Try what I had suggested with your multimeter...remove the fuse and see which of the 2 pins feeds the light....connect either lead of the multimeter to that one....the other should be HOT AT ALL TIMES...remove the LED light....now connect the other lead of the multimeter to the frame rail somewhere under the hood...find a CLEAN ground point....the multimeter should show "OL" ohms....or however your multimeters shows an open circuit ....you SHOULD have an open circuit !!....PCM has NOTHING to do with your issue !!...if you have a partial short to ground your 12 volts is partially getting pulled to ground...7 volts of it !!
Try what I had suggested with your multimeter...remove the fuse and see which of the 2 pins feeds the light....connect either lead of the multimeter to that one....the other should be HOT AT ALL TIMES...remove the LED light....now connect the other lead of the multimeter to the frame rail somewhere under the hood...find a CLEAN ground point....the multimeter should show "OL" or "0"....however your multimeters shows an open circuit....you SHOULD have an open circuit !!....PCM has NOTHING to do with your issue !!...if you have a partial short to ground your 12 volts is partially getting pulled to ground...7 volts of it !!
I would do that but I can't remove the LED light. I stupidly hardwired a small LED strip into the housing.
Would an open circuit eventually cause problems with other lights in the circuit?
I'd like to just cap off the factory wires and source a new power and ground for the hood lamp. But If it is an open circuit, I don't want it to eventually effect my glovebox and RV mirror lights. They seem to be working fine right now though.
I would do that but I can't remove the LED light. I stupidly hardwired a small LED strip into the housing.
Would an open circuit eventually cause problems with other lights in the circuit?
I'd like to just cap off the factory wires and source a new power and ground for the hood lamp. But If it is an open circuit, I don't want it to eventually effect my glovebox and RV mirror lights. They seem to be working fine right now though.
.
I believe there is a connector on the right side of the hood by the air filter that goes to the light...just disconnect it there and test !!...a dead short would have most likely blown the fuse !!....AND WHEN YOU REMOVE THE FUSE SEE IF YOU HAVE 12 VOLTS ON ONE SIDE OF THAT CIRCUIT !!...if 5 volts there you have to look upstream....micro relay 37 (MONITORED LD)
I believe there is a connector on the right side of the hood by the air filter that goes to the light...just disconnect it there and test !!...a dead short would have most likely blown the fuse !!....AND WHEN YOU REMOVE THE FUSE SEE IF YOU HAVE 12 VOLTS ON ONE SIDE OF THAT CIRCUIT !!...if 5 volts there you have to look upstream....micro relay 37 (MONITORED LD)
i was getting 5 volts at every plug connection I could reach.
I will have to test the circuit like you said to do.
Other lights in the circuit connected to that fuse are operating just fine.
But Maybe my other lights are on with 5 volts but would be brighter with 12v.
If I do get 12v at the fuse, would it be safe to simply cap off the factory power and ground for the hood lamp and leave them secured?
i didn’t read your post in time and I just hardwired the light to a factory ground and the fuse box constant.
I wish I had listened to your post earlier but what’s done is done. And I guess I have a super bright hood light now.. haha
i was getting 5 volts at every plug connection I could reach.
I will have to test the circuit like you said to do.
Other lights in the circuit connected to that fuse are operating just fine.
But Maybe my other lights are on with 5 volts but would be brighter with 12v.
If I do get 12v at the fuse, would it be safe to simply cap off the factory power and ground for the hood lamp and leave them secured?
i didn’t read your post in time and I just hardwired the light to a factory ground and the fuse box constant.
I wish I had listened to your post earlier but what’s done is done. And I guess I have a super bright hood light now.. haha
check for a partial short to ground with the ohm meter function first and then go from there !!...and remember to do the check BOTH ends of the circuit need to be isolated !!
check for a partial short to ground with the ohm meter function first and then go from there !!...and remember to do the check BOTH ends of the circuit need to be isolated !!
After I find which end of the circuit the short is coming from, do I simply start tracing wires down? Sorry I’m pretty new when it comes to electrical
The short can be anywhere along the path of the wire and don’t worry about your electrical knowledge...MANY, even auto techs fall short !!....hope this video helps !!
I found the lighting wiring for your '98....it looks like it may be a little difficult to "isolate" that circuit since the inside rearview mirror, vanity mirrors, and the underhood light are all on the same circuit...just might have to remove all those bulbs
I found the lighting wiring for your '98....it looks like it may be a little difficult to "isolate" that circuit since the inside rearview mirror, vanity mirrors, and the underhood light are all on the same circuit...just might have to remove all those bulbs
If you say it may be difficult, I certainly believe it.
Currently, the light gets power from the fuse box constant side with an inline fuse and manual switch. And is grounded on the factory ground behind the passenger headlight.
I’d like to keep it this way if possible because the old wire seems to be on its way out.
I know most people don’t bother with the hood lamp, but I like it.
Do you see a problem with having the hood lamp wired this way?
Testing the RV mirror lights I’m getting 12v. The other lights on the circuit work normally. Would it be safe to say that the short must be closer to the hood lamp and might not effect the other lights?
If I’m lucky, maybe I can find the bad wire? Snip / cap the wires and tie them back into the factory loom like they never existed? Or it’s not that simple?
Thank you for all your response! I apologize for the lack of electrical knowledge. I just don’t want to potentially short out other components or cause a fire.
I’ll get down there with the multi meter at some point today
It CAN NOT be a partial short to ground causing a 7V drop. Saying that it's a partial short that causes a 7V drop makes no sense. Drawing enough current on a wire to drop 7V would quickly blow the fuse. 5' of 18 gauge wire has a resistance of 0.03 ohms. So, using ohms law - 7V / 0.03 ohms = 233A. Even assuming the total circuit including connections had say 0.25 ohms of resistance instead it'd still be a 28A draw.
It might be a weak connection that has resistance, but that should measure 12V with no load and then drop voltage when you apply a load.
That isn't the schematic for the under hood light either. The underhood light isn't on that schematic page and the underhood light works independently of the interior lights. BCM will switch that relay on and off to turn the interior lights on and off which would mean the underhood light would only light when the interior lights were on if it was controlled by that relay.
It CAN NOT be a partial short to ground causing a 7V drop. Saying that it's a partial short that causes a 7V drop makes no sense. Drawing enough current on a wire to drop 7V would quickly blow the fuse. 5' of 18 gauge wire has a resistance of 0.03 ohms. So, using ohms law - 7V / 0.03 ohms = 233A. Even assuming the total circuit including connections had say 0.25 ohms of resistance instead it'd still be a 28A draw.
It might be a weak connection that has resistance, but that should measure 12V with no load and then drop voltage when you apply a load.
That isn't the schematic for the under hood light either. The underhood light isn't on that schematic page and the underhood light works independently of the interior lights. BCM will switch that relay on and off to turn the interior lights on and off which would mean the underhood light would only light when the interior lights were on if it was controlled by that relay.
Is this
the "underhood light" on the 2nd page of the PDF ???...just asking.
Hood Lamp Problem
