Main fuse box issue
#1
Main fuse box issue
Hey guys I have a issue that is wierd. The main fuse box in my car is overheating and burning literally. After I drive for a while and the fuse box getnice and hot enough to start smoking then my voltage starts dropping. It gets as low as 8.3 but it doesnt die out I throw it into Neutral and rev it up to maintain the voltage. As long as I am in motion and on the gas pedal than the voltage is fine. But as soon as I get off than the voltage drops. The little battery light on the guages has come on for me. I have had the battery checked and it is good. I went to my mechanic and he said that the main fuse box has to be replaced. The ground on it has burned out. The little screw next to th Alt fuse is where the ground is and that burned. Anyone have any insight or experience with this issue?? My mechanic said that I need a new fuse box. Lexus doesnt sell them they only sell the plastic parts the the fuses go into but no internals. They said that I would have to swap them from the original but How do I do that when my original is f-ed? I would have to purchase one from a junkyard that is my only option. Please someone help. BTW the car is a 2000 Lexus GS400 with 52000 miles.
#2
Moderator
Start by islolating the problem ... which fuse and under what conditions.
Measure current through each fuse. A smart tech with the low voltage range can tell the voltage drop being developed across the fuse box and or fuse. If it has smoked, you should be able to locate melted insulation on wire and trace it.
Either some thing is drawing too much current or some connector is loose in the fuse box. Loose fuse and fuse-end connectors can also be the cause. Also if any fuse was replaced, the new one may not have the right thickness or there could be crud from past.
Salim
Measure current through each fuse. A smart tech with the low voltage range can tell the voltage drop being developed across the fuse box and or fuse. If it has smoked, you should be able to locate melted insulation on wire and trace it.
Either some thing is drawing too much current or some connector is loose in the fuse box. Loose fuse and fuse-end connectors can also be the cause. Also if any fuse was replaced, the new one may not have the right thickness or there could be crud from past.
Salim
#3
Start by islolating the problem ... which fuse and under what conditions.
Measure current through each fuse. A smart tech with the low voltage range can tell the voltage drop being developed across the fuse box and or fuse. If it has smoked, you should be able to locate melted insulation on wire and trace it.
Either some thing is drawing too much current or some connector is loose in the fuse box. Loose fuse and fuse-end connectors can also be the cause. Also if any fuse was replaced, the new one may not have the right thickness or there could be crud from past.
Salim
Measure current through each fuse. A smart tech with the low voltage range can tell the voltage drop being developed across the fuse box and or fuse. If it has smoked, you should be able to locate melted insulation on wire and trace it.
Either some thing is drawing too much current or some connector is loose in the fuse box. Loose fuse and fuse-end connectors can also be the cause. Also if any fuse was replaced, the new one may not have the right thickness or there could be crud from past.
Salim
#4
Moderator
There are 60amp fuses which support 35amp (guess) normal flow. Once you have a bad connection (0.08 ohms) you get 3v drop and 105watts of heat is produced. All this and no fuse pops.
Before replacing the fuse box, clean the wire terminals also ensure that right rated fuses exist in all fuse boxes. You should disconnect any and all (non oem) electrical devices. If something has been rewired, ensure proper fuse exists ... as close to the junction point (electrically closer to the battery, and farthest from the actual load .. this simple thing protects the shorts in the wiring and not just the oveload).
Good luck and happy hunting.
Salim
Before replacing the fuse box, clean the wire terminals also ensure that right rated fuses exist in all fuse boxes. You should disconnect any and all (non oem) electrical devices. If something has been rewired, ensure proper fuse exists ... as close to the junction point (electrically closer to the battery, and farthest from the actual load .. this simple thing protects the shorts in the wiring and not just the oveload).
Good luck and happy hunting.
Salim
#6
Moderator
May be not, BUT
Cars are hostile environment. Vibration and motion rubs the jacketted wires and over time insulation can be compromised .. [BMW owners can comment on this issue].
My suggestion was to start out with stock environment and bring other on line one at a time.
If the stock environement causes problems you will may have to take stock fuses out to narrow down to a perticular malfunctioning circuit.
Salim
Cars are hostile environment. Vibration and motion rubs the jacketted wires and over time insulation can be compromised .. [BMW owners can comment on this issue].
My suggestion was to start out with stock environment and bring other on line one at a time.
If the stock environement causes problems you will may have to take stock fuses out to narrow down to a perticular malfunctioning circuit.
Salim
#7
well I put in the new fuse box and you were right I still have the same problem. I need to try to narrow down what is causing it. I also have some kind of drain on the battery that needs to be located. I am attaching pics of how bad my fuse box got. Excuse the pics they were taken with my phone.
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#8
Moderator
Please be aware that there is a potential for fire.
Dumb question: Is the + and - of the battery the right way?
Time to get hold of wiring diagram.
Disconnect alternator and remove ALL fuses in the block you just replaced.
I strongly suspect some thing is shorting before you reach the distribution box (the other fuse box). With this high current I would expect some tell tale signs at the actual problem location. Smell the alternator for burnt out diodes.
One thing that might give you some clue is, does the problem happen after you turn the ignition or even in off position.
Salim
Dumb question: Is the + and - of the battery the right way?
Time to get hold of wiring diagram.
Disconnect alternator and remove ALL fuses in the block you just replaced.
I strongly suspect some thing is shorting before you reach the distribution box (the other fuse box). With this high current I would expect some tell tale signs at the actual problem location. Smell the alternator for burnt out diodes.
One thing that might give you some clue is, does the problem happen after you turn the ignition or even in off position.
Salim
#9
Lexus Fanatic
that looks bad. I wouldn't drive it like that, you may blow out something very expensive like the ecu. I'd start by disconnecting anything aftermarket. imo, something is loose,shorting out,or drawing too much current.
#10
welll I'm going to an audio shop tommorrow in which the guy is an expert in locating shorts and electrical issues like this. BUt I have disconnected the amps and it is not them. I havent yet disconnected the Avic-n1 but I dont think that its it, I've had it installed in 3 of my previous cars and no problems. I will see tommorrow what happens and hopefully they can locate the problem. In the engine bay the only thing that smells is the actual fuse box and nothing else.
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