4th gen FAQs problem!! rewired corner blubs v.s. fuse voltage!!!
4th gen FAQs problem!! rewired corner blubs v.s. fuse voltage!!!
Originally posted by ericdwong
I was working on my friend's 98 Max rewiring the corners to utilize the 27 watt side of the bulb, but I had the problem that I kept on blowing the 7.5 amp "tail" fuse on his car. I thought I had done something wrong and that the wire kept grounding out. This one had me really puzzled, cause my rewired corners have been rewired for over a year with no problems at all. There was one variable that I did not account for, was that he was running side marker lamps. I got technical and brought out my basic EE skills. In a 14.4 volt system, one watt is equal to about .06944444 amps. Since they are light bulbs, the tolerance isnt as tight as say a computer's power supply. Anyway, the tail light fuse is 7.5 amps, and it includes the corner light, the front marker light, the rear marker light, tail lights and the license tag lights. On my car (without side markers), with the rewired wattage of 27 watts and all the other bulbs using aboug 5 watts, this comes out to about 104 watts being consumed. Since watts= amps x volts, here 104 watts divided by 14.4 draws about 7.2 amps it is not enough to blow the 7.5 amp fuse. Now since my friend has 10 measily additional watts for his side markers, this brings the equation to 114 divide by 14.4 equals 7.919 amps that WAS enough to blow the 7.5 amp fuse. No wonder I was sitting there scratching my head why his fuse kept blowing. It also explains why when he took out one of the 27 watters (which we thought was grounding out), it didnt blow, cause that would have put him well under 7 amps. We replaced it with a 10 amp fuse, and so far its still working. I believe the 10 amp fuse should be OK for his wires, but I told him since we did up the wattage to check the wires to make sure nothing is melting. So, if you rewire your corners and have side markers or additional lights wired to the tail light circuit and you scratch your head why its blowing, this is the reason why. All it took was an additional 10 watts. Same thing if you run trailer lights on the "tail" circuit.
I was working on my friend's 98 Max rewiring the corners to utilize the 27 watt side of the bulb, but I had the problem that I kept on blowing the 7.5 amp "tail" fuse on his car. I thought I had done something wrong and that the wire kept grounding out. This one had me really puzzled, cause my rewired corners have been rewired for over a year with no problems at all. There was one variable that I did not account for, was that he was running side marker lamps. I got technical and brought out my basic EE skills. In a 14.4 volt system, one watt is equal to about .06944444 amps. Since they are light bulbs, the tolerance isnt as tight as say a computer's power supply. Anyway, the tail light fuse is 7.5 amps, and it includes the corner light, the front marker light, the rear marker light, tail lights and the license tag lights. On my car (without side markers), with the rewired wattage of 27 watts and all the other bulbs using aboug 5 watts, this comes out to about 104 watts being consumed. Since watts= amps x volts, here 104 watts divided by 14.4 draws about 7.2 amps it is not enough to blow the 7.5 amp fuse. Now since my friend has 10 measily additional watts for his side markers, this brings the equation to 114 divide by 14.4 equals 7.919 amps that WAS enough to blow the 7.5 amp fuse. No wonder I was sitting there scratching my head why his fuse kept blowing. It also explains why when he took out one of the 27 watters (which we thought was grounding out), it didnt blow, cause that would have put him well under 7 amps. We replaced it with a 10 amp fuse, and so far its still working. I believe the 10 amp fuse should be OK for his wires, but I told him since we did up the wattage to check the wires to make sure nothing is melting. So, if you rewire your corners and have side markers or additional lights wired to the tail light circuit and you scratch your head why its blowing, this is the reason why. All it took was an additional 10 watts. Same thing if you run trailer lights on the "tail" circuit.
Senior Member
Joined: Jan 2002
Posts: 419
Are you asking if it's okay to put a 30 amp fuse where there used to be a 7.5? Stuff will still work with a higher amp fuse, but it's not a good idea. The lower amp fuse was chosen for a reason. If you're using a fuse that is 20 amps more than what is necessary, and then a small wire shorts out, the fuse will take longer to burn out, if it burns at all. This could cause wires to melt or even start a fire. You really should use the smallest fuse you can that doesn't burn when the lights are turned on.
Originally posted by Prolepsis
Are you asking if it's okay to put a 30 amp fuse where there used to be a 7.5? Stuff will still work with a higher amp fuse, but it's not a good idea. The lower amp fuse was chosen for a reason. If you're using a fuse that is 20 amps more than what is necessary, and then a small wire shorts out, the fuse will take longer to burn out, if it burns at all. This could cause wires to melt or even start a fire. You really should use the smallest fuse you can that doesn't burn when the lights are turned on.
Are you asking if it's okay to put a 30 amp fuse where there used to be a 7.5? Stuff will still work with a higher amp fuse, but it's not a good idea. The lower amp fuse was chosen for a reason. If you're using a fuse that is 20 amps more than what is necessary, and then a small wire shorts out, the fuse will take longer to burn out, if it burns at all. This could cause wires to melt or even start a fire. You really should use the smallest fuse you can that doesn't burn when the lights are turned on.
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