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I added in-line fuses to the "red" wires of my lighting system on my 1965 BJ8 last summer after a melt-down - at the time I thought that a failed headlight switch was the cause as it had melted down. I installed 10 amp fuses which seemed to work fine - until last weekend I was told I had an inop right brake light. Assuming a burned out bulb I soon discovered that there was more to it. I had a left brake light and left signal, but no tail lights on the left or any function on the right brake/tail and signal light. The short version is that I closely inspected all of the wiring in the trunk area and found the license plate illumination light red wire had overheated at some point - I had not noticed that last summer, but it could have been oversight. It didn't look like it had shorted per se, but I replaced that wire last night and checked all the grounds. I had installed an in-line fuse on the red wire just prior to it splitting off to the tail lights (located beside the gas tank). That 10 amp fuse had blown. Now here is the part I don't understand: I also have another in-line fuse on the same wire in the engine compartment where it splits off and goes to the rear. This 10 amp fuse had also blown. Why would BOTH fuses blow? I could find no short in the trunk area so I am guessing that there is a short between the two fuses somewhere (where the wire runs from the engine compartment back along the frame and into the trunk). Does this make sense - you have probably figured out already that my strong suit is NOT wiring..... Anyway, any ideas on what would cause the TWO fuses to blow (I have always thought that only one would blow at a time) and what is a good fuse amp size for these in-line fuses? Also - why did the left brake and signal light still work??? Thank you very much for your help! /ubbthreads/images/graemlins/confused.gif
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In-Line Fuses
- Thread starter stever
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Hello Stever,
If I understand you correctly, the two fuses supply the same circuit. i.e. the fuses are in series. Well, they are both carrying the same current and if it exceeds their rating both will blow. Basically, one is redundant. The reason your brake and indicator work is because they are not supplied from the lighting circuit.
Alec
If I understand you correctly, the two fuses supply the same circuit. i.e. the fuses are in series. Well, they are both carrying the same current and if it exceeds their rating both will blow. Basically, one is redundant. The reason your brake and indicator work is because they are not supplied from the lighting circuit.
Alec
Thanks, Piman, I put one fuse at one end and another at the other because it is a long wire and didn't want another meltdown. I thought that the closest fuse to the short would blow first and therefore give me an indicator of the location. But, I guess I was wrong. However, I still don't understand why the right brake light didn't work as it is not powered by the lighting circuit either. In other words, why did the left brake light work and not the right? Seems to me that either both or neither would work. Thanks again!
dklawson
Yoda
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If you put two fuses in series, consider using two different ratings with the smaller Amp fuse close to the load (lamps). The smaller fuse should blow first IF they are of the same "type" (i.e., don't use both fast- and slow-blow fuses on the same circuit).
10 Amps is a huge load for tail lamps. Consider 60 Watt headlamps, 60 W / 12V = 5 Amps... and that's a headlamp... not a tail lamp. I know you've checked the wiring but sit down with your schematic and look at what else may be connected to the circuit... what other lamps "T" off that red line? Look for some place along the overheated wire that may have touched chassis ground. Look at all the grommets where the wire passes through sheet metal for possible damage there. You mentioned the license plate lamp wire overheated. On old Minis (of the same period as your car) that wire has been known to short out to the boot-lid.
You mentioned that you checked your ground connections. I run multiple/extra ground wires for most items where I suspect their may be a ground connection problem. So far the only thing I lost was my high-beam indicator on the dash... a little paint scraping and it was working again also.
You mentioned that last year you had a failed headlight switch. This is a common problem in most older British cars. The best solution for it is to build a small relay panel for the headlamps so that only control current for the relays flows through the dash switch. The relays can usually be hidden somewhere in the engine compartment to keep an original appearance.
10 Amps is a huge load for tail lamps. Consider 60 Watt headlamps, 60 W / 12V = 5 Amps... and that's a headlamp... not a tail lamp. I know you've checked the wiring but sit down with your schematic and look at what else may be connected to the circuit... what other lamps "T" off that red line? Look for some place along the overheated wire that may have touched chassis ground. Look at all the grommets where the wire passes through sheet metal for possible damage there. You mentioned the license plate lamp wire overheated. On old Minis (of the same period as your car) that wire has been known to short out to the boot-lid.
You mentioned that you checked your ground connections. I run multiple/extra ground wires for most items where I suspect their may be a ground connection problem. So far the only thing I lost was my high-beam indicator on the dash... a little paint scraping and it was working again also.
You mentioned that last year you had a failed headlight switch. This is a common problem in most older British cars. The best solution for it is to build a small relay panel for the headlamps so that only control current for the relays flows through the dash switch. The relays can usually be hidden somewhere in the engine compartment to keep an original appearance.
Hello Steve,
the reason the right side brake light does not work is likely to be a poor earth of that light unit. Because you say that the left indicator works and the right doesn't points to an earth rather than fed problem. Of course it's possible that the bulbs are both gone! One fuse is all that is needed and the load is about 24 watt = 2 amps. However , I would say that 10 amps is a good fuse size as it will protect the loom in a short circuit situation and is less likely to nuisance blow with age and vibration.
Alec
the reason the right side brake light does not work is likely to be a poor earth of that light unit. Because you say that the left indicator works and the right doesn't points to an earth rather than fed problem. Of course it's possible that the bulbs are both gone! One fuse is all that is needed and the load is about 24 watt = 2 amps. However , I would say that 10 amps is a good fuse size as it will protect the loom in a short circuit situation and is less likely to nuisance blow with age and vibration.
Alec
GregW
Yoda
Offline
Hi Stever,
I have a 67 BJ8, so my wiring may be a little different. The red wire is for the running lights. You may have left the front lights unfused depending on where you placed the fuse in the engine compartment. On my car the brake wire is the green/purple wire. The brake circuit is fused at the main fuse block (along with everything else but the horn on one fuse) I agree with Doug on the 5 amp fuse. I think the brake lights are 21 watts each. I made a color wiring diagram a few years back that may help you. You can find it here. www.team.net/www/healey/tech/big_hly/electric/wiring_diagram.html
I have a 67 BJ8, so my wiring may be a little different. The red wire is for the running lights. You may have left the front lights unfused depending on where you placed the fuse in the engine compartment. On my car the brake wire is the green/purple wire. The brake circuit is fused at the main fuse block (along with everything else but the horn on one fuse) I agree with Doug on the 5 amp fuse. I think the brake lights are 21 watts each. I made a color wiring diagram a few years back that may help you. You can find it here. www.team.net/www/healey/tech/big_hly/electric/wiring_diagram.html
Thank you all for your help! I think I have the problem on my car "fixed". I believe I had a ground problem on the right tail lamp that caused the non-op brake light. I think the short causing the fuses to blow was at the connection for the license plate light. I replaced that wire and connectors, checked all connections and wires and checked all of the grounds. After replacing the fuses all ops checked "OK". I still have not inspected the wire under the car from the engine bay, but plan to do that very soon as there could be an intermittent type of short somewhere along there. Anyway, as of now the brake lights, tail lamps and signal lamps are working properly. Thank you all again for your help!
Well, guess what - I still have the brake light problem. However, all of the other issues are solved. What I don't understand on this is why it seems to be "intermittent" to some degree. I have just recieved my heritage certificate which provides the reason why I have "early BJ8 wiring" - it was built in '64 not '65! Hey my car is a year older than I thought.... Anyway, the fact that the signal light and tail lights work tells me that the ground is good. Correct assumption? I have to think that the culprit may be the flasher relay unit which in dual use lamps (lights and brake and signal) interrupts the brake input so the flash for the signal can occur. Now, my question here is: Is it possible for the brake flasher unit to fail in an intermittent manner? I intend to trouble shoot the brake flasher unit IAW workshop manual and Norm's Tech Tips, etc. so I may find more. However, if it can "intermittently" fail then it may check out "OPS OK" during the troubleshooting and still cause problems.... thanks in advance for any inputs!
I want to thank all of you that provided me help on this problem! Really appreciate you all on this forum. I think I have it fixed. I say "think" because on my car you never really know! For example, at one point in my trouble-shooting this problem the whole system stopped - of course it was the main fuse not connecting well. I don't know why my main fuses do that occasionally. They are clean and all but sometimes I need to move them a little and reseat them and then all is well again - usually until the car sits a few months. Anyway, I isolated the problem as the flasher relay. Took it off the car and cleaned up the points with emory cloth refit it and it Ops Checked "good". I haven't driven her since, but wanted to let you know that evidently the flasher relay can fail in an intermittent fashion. Hope it stays fixed this time! Thank you again for your help.
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Stever,
--------- GOOD SHOW ------- You're doing great !!!!
--------- GOOD SHOW ------- You're doing great !!!!
Thank you, Dave! I have to admit sometimes that I feel less than wonderful when I realize that I, myself, "am the stupid PO"...... I think I have made virtually every "stupid PO" mistake that has been made - after 32 years of working on my BJ8 I have had lots of opportunity to make them!! Your kind comment has "made my day" - I was really pretty thrilled to "fix" an electrical component rather than just "write a check" to buy a new one. Thanks again to all those great guys/gals on this forum!
anthony7777
Yoda
Offline
greg,just checked out your wiring diagram,nice,like it,will us it,very helpfull,thanks,p.s. my mother in law is asking about you! /ubbthreads/images/graemlins/cheers.gif
tahoe healey
Yoda
Offline
GregW, that was a great wiring diagram. I see where you fused the plate light wire. Where else have you placed the fuses? I would like to add some to the head lamps and tail lights also. What other circuits have others done? And what amps on each?
GregW
Yoda
Offline
Hi TH,
Actually the lic. plate fuse is in the manual, not my mod. I think European cars had them? I couldn't figure out why they fused only one bulb. I made a 10-fuse block for my car (see attachment) that fits in the same place on the firewall without having to relocate anything. It's made from 2 cut up 6-fuse blocks so I have both switched and unswitched circuits in one place. Michael Oritt has the same 2 fuse blocks that he didn't cut up, so he's got 2 additional circuits. Since he had done this already, he gave me the following fuse numbers saying that some may be a little high but the fuse will still blow before the smoke gets out.
Switched: wiper-10, aux cooling fan-15, radio-20, heater-10, fuel pump-5, flasher-10. Unswitched: radio mem-5, fog lights-25, headlights-30, horn-20, lighter-5.
For the headlights I disconnected the power from the regulator and ran a wire to the new fuse block.
Actually the lic. plate fuse is in the manual, not my mod. I think European cars had them? I couldn't figure out why they fused only one bulb. I made a 10-fuse block for my car (see attachment) that fits in the same place on the firewall without having to relocate anything. It's made from 2 cut up 6-fuse blocks so I have both switched and unswitched circuits in one place. Michael Oritt has the same 2 fuse blocks that he didn't cut up, so he's got 2 additional circuits. Since he had done this already, he gave me the following fuse numbers saying that some may be a little high but the fuse will still blow before the smoke gets out.
Switched: wiper-10, aux cooling fan-15, radio-20, heater-10, fuel pump-5, flasher-10. Unswitched: radio mem-5, fog lights-25, headlights-30, horn-20, lighter-5.
For the headlights I disconnected the power from the regulator and ran a wire to the new fuse block.