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queeniee
19-08-10, 08:36 PM
Every time I use my road lights in the High Beam position, the fuse (16 Amps) blows after 20-30s. . I have Lucas sealed beams. My road (low) beams work fine.
My battery is 12 V, 70 Amps.
I have a spare Lucas beam for testing the system.
What do you suggest for finding where the electrical bug stands?
In principle, with 2 X 100 Watt lights, a 17 Amps fuse should be sufficient.And I think that the Lucas sealed beams are really under 65W.
This prevents me from night driving and your suggestions will be welcome!!!

Purple AK
19-08-10, 08:49 PM
Hi Queenie. If it takes 20-30 secs to blow the fuse my money would be on a high resistance/dirty joint/corrosion in one of the high beam connections.
PS. This could also be on the earth side. But I would have thought it would do on Low Beam if it was.

queeniee
19-08-10, 08:57 PM
Hi Queenie. If it takes 20-30 secs to blow the fuse my money would be on a high resistance/dirty joint in one of the high beam connections.
PS. This could also be on the earth side. But I would have thought it would do on Low Beam if it was.
OK, tomorrow, I will check the condition of the connections. I suspect them to be corroded . You gave me a good idea; I shall check all the earth side connections. I shall tell you results tomorrow, I will go to my car tomorrow at 6.30 AM and spend the whole day on this problem.
I hate electrical gremlins..
Thanks , Purple AK!!!

wilf
19-08-10, 08:59 PM
Sorry Chris, but the fuse is blowing due to excess current. High resistance joints reduce current, and so by themsleves can not be a primary cause of fuse failure.

Unless............the high resistance joint is very close to the fuse (like the fuseholder itself) and heating it up considerably.

Queenie, you need a good quality AVO meter and find out exactly what current is flowing where. Take each headlamp bulb out in turn to see if there is equal current through the fuse for each, as a start.

Find out what else that fuse is feeding in addition to the headlights - if , for example, it is feeding the ingition circuit as well, you will be overloading it.

Purple AK
19-08-10, 09:10 PM
Sorry Chris, but the fuse is blowing due to excess current. High resistance joints reduce current, and so by themsleves can not be a primary cause of fuse failure.

Unless............the high resistance joint is very close to the fuse (like the fuseholder itself) and heating it up considerably.

Queenie, you need a good quality AVO meter and find out exactly what current is flowing where. Take each headlamp bulb out in turn to see if there is equal current through the fuse for each, as a start.

Find out what else that fuse is feeding in addition to the headlights - if , for example, it is feeding the ingition circuit as well, you will be overloading it.
You are right! It's amazing how much information has from slipped from the memory bank in the 40 years since I did an electronic apprentiship :cry: I should have been paying more attention, rather than chasing wimmins :rolleyes: :D

mylesdw
19-08-10, 09:27 PM
Is this a new problem or has it always been there? Does the fault occur with or without the engine running?

shadow
19-08-10, 09:49 PM
I'm working in Paris, Will have a word with some of the guys, sure we have a car spark amongst us if you get stuck. We are by the Pantheon/Library tomorrow.

pat b
19-08-10, 10:06 PM
I'm working in Paris, Will have a word with some of the guys, sure we have a car spark amongst us if you get stuck. We are by the Pantheon/Library tomorrow.You spend so much time at home doing f-all you cant help showing off when you finally get out and do some work ( & I have been on enough film sets to know how hard you are working now :p:p:p ) PAT

shadow
19-08-10, 10:34 PM
only trying to help. didnt say what i wasnt doing did I? And its always the drivers who eat all the fkin food.

Back on topic.....

queeniee
20-08-10, 08:44 PM
Sorry Chris, but the fuse is blowing due to excess current. High resistance joints reduce current, and so by themsleves can not be a primary cause of fuse failure.

Unless............the high resistance joint is very close to the fuse (like the fuseholder itself) and heating it up considerably.

Queenie, you need a good quality AVO meter and find out exactly what current is flowing where. Take each headlamp bulb out in turn to see if there is equal current through the fuse for each, as a start.


Find out what else that fuse is feeding in addition to the headlights - if , for example, it is feeding the ignition circuit as well, you will be overloading it.
The fuse blows even when the engine is not running.
The idea of a bad fuseholder deserves attention since mine is very old and looks in a sad condition.

After trying another fuse (25 Amps), it blew within 2 sec and after that I got nothing remaining:
No high beams, no low beam, no parking lights. All other electrical circuits are working fine: horn, electrical fans, ignition.
The contacts on the beam lights were very corroded. I cleaned them, made some soldering ( the ground wire of the headlight was almost cut) but this was not sufficient.
I thought the high-low switch located on the floor and foot actuated might be guilty. This is not the case : I used a spare third headbeam and a spare battery and it worked in high and low position.
Tomorrow or Sunday I shall get a good meter and check the currents. I have been on it since this morning and just arrived home to read your ideas. Thanks. I shall tell you more Monday, I hope.

Delfim
20-08-10, 08:55 PM
Check the tail lights and the licence plate connecttions as well

queeniee
21-08-10, 08:08 AM
Check the tail lights and the licence plate connecttions as well
Tail lights and plate light operating normally and dashboard light work. I shall check stop lights today and this morning, I go buying a meter and a few yards of wire.

BLOKE
21-08-10, 09:22 AM
You are doing this wrong, as said before any poor joints would add resistance and draw LESS current, so fuse would not blow.
Go back and start again, add up all the bulbs on that circuit, use volts times watts equals amps. as it may be that you actually need a bigger fuse than you are using.
The next consideration is in-rush, until the bulbs light up they pull a lot more current.
if you are unable to do this yourself, send me a PM listing all the devices on this circuit and I will calculate it for you.
one thing you could try in the meantime is to remove one bulb and try it, then replace it and try the next, this will ID the fault if it is only one line that is at fault.
Regards Frank Dowsett. BLOKE.

Purple AK
21-08-10, 10:14 AM
You are doing this wrong, as said before any poor joints would add resistance and draw LESS current, so fuse would not blow.
Go back and start again, add up all the bulbs on that circuit, use volts times watts equals amps. as it may be that you actually need a bigger fuse than you are using.
The next consideration is in-rush, until the bulbs light up they pull a lot more current.
if you are unable to do this yourself, send me a PM listing all the devices on this circuit and I will calculate it for you.
one thing you could try in the meantime is to remove one bulb and try it, then replace it and try the next, this will ID the fault if it is only one line that is at fault.
Regards Frank Dowsett. BLOKE.
Think you'll find its Watts divided by Volts = Amps ;)

slogger
21-08-10, 11:21 AM
Quite right Chris, so you remember something!;):D

From all of the above and various electrical faults in the past, two things spring to mind. First is unusual but have come across this. One of the lamps becomes low resistance through a manufacture fault or partial failure of the filament or filament carrier. Second, a damaged cable was found. Could there be more damage somewhere else? A resistive connection to ground could exist and the addition of the lighting load takes the fuse. This resistive connection could also be a switch contact fault. Fords had a habit of melting their high beam switch contact carrier and would either stop working or blow a fuse.

Just a thought.

As for inrush currents, 2.5x rated current is a good starting point with DC, but automotive fuses are designed to cope with this. They fall into the anti-surge class of fuses.

queeniee
21-08-10, 06:36 PM
Quite right Chris, so you remember something!;):D

From all of the above and various electrical faults in the past, two things spring to mind. First is unusual but have come across this. One of the lamps becomes low resistance through a manufacture fault or partial failure of the filament or filament carrier. Second, a damaged cable was found. Could there be more damage somewhere else? A resistive connection to ground could exist and the addition of the lighting load takes the fuse. This resistive connection could also be a switch contact fault. Fords had a habit of melting their high beam switch contact carrier and would either stop working or blow a fuse.

Just a thought.

As for inrush currents, 2.5x rated current is a good starting point with DC, but automotive fuses are designed to cope with this. They fall into the anti-surge class of fuses.

I was taking just twice the rating current. Each lamp works fine separately but not together.
But I found guilty wire between the two headlights, they are running too close to the hood articulation (hinge) and was almost bare. Replacing it with a new wire worked. But I realized that I should be serious and clean or replace many connectors. Not too enthousiastic about that but it has to be done.
Thanks for your advices, this gave me good ideas as usual and the forum is a great place for transmitting experience.

queeniee
21-08-10, 06:37 PM
Think you'll find its Watts divided by Volts = Amps ;)
This is like re-discovering Ohm's law...

queeniee
21-08-10, 06:43 PM
You are doing this wrong, as said before any poor joints would add resistance and draw LESS current, so fuse would not blow.
Go back and start again, add up all the bulbs on that circuit, use volts times watts equals amps. as it may be that you actually need a bigger fuse than you are using.
The next consideration is in-rush, until the bulbs light up they pull a lot more current.
if you are unable to do this yourself, send me a PM listing all the devices on this circuit and I will calculate it for you.
one thing you could try in the meantime is to remove one bulb and try it, then replace it and try the next, this will ID the fault if it is only one line that is at fault.
Regards Frank Dowsett. BLOKE.
It is one thing I forgot to write in my first post: I checked the bulbs and sealed beams separately, fed by an external battery (through a fuse). They were fine when not connected to the car's system.

Purple AK
21-08-10, 06:53 PM
This is like re-discovering Ohm's law...
It's all coming back to haunt me!! Ohms Law! Watts Law! Joules Law! then Faraday popped up! :-? I'll be dreaming Resistor Colour Codes next :D

BLOKE
21-08-10, 07:37 PM
Well done Chris, you picked up the "deliberate " mistakeIi planted for you.
Frank. BLOKE.

Purple AK
21-08-10, 07:50 PM
Well done Chris, you picked up the "deliberate " mistakeIi planted for you.
Frank. BLOKE. Do I get a prize? :D No, I thought not ;)

queeniee
21-08-10, 07:55 PM
Do I get a prize? :D No, I thought not ;)
A gold medal? The Fields medal has just been won this year by 2 frenchies.

queeniee
21-08-10, 07:57 PM
I was just wondering if such a thing as a wiring diagram for RAM exists. My guess would be "no".......
I think every individual owner- builder has its own.

Purple AK
21-08-10, 08:04 PM
A gold medal? The Fields medal has just been won this year by 2 frenchies.
Sadly I'm 18 years too old to qualify for a Fields Medal :rolleyes: :D

gilby
31-08-10, 10:32 AM
i've a wiring diagram !
i've just fitted xenon in my original headlamps....it's "Versailles" now !
I' ve not "adverse flashes" so it's ok for the other drivers and it's possible to use the RAM "normally" at full speed on nignt driving

bitsilly
31-08-10, 04:17 PM
Hi Queenie,
been away so just picked this up.
I know this may sound dull, but the first thing I would do is follow the wires and check for the obvious.
I had a fault which turned out to be the fog light. I had thought it would not matter which was live and which was return, little knowing the return was also earthed by one of the mounting screws! So I was earthing a live.
The thing is a fault like that can do things like slow the fuel pump if it drains current, so it often seems like a dark science!
Have you added or changed anything electrical recently (seemingly unrelated).

I had a loom built to suit the Ram from Thunder road. It was nearly perfect, and the chap who built it knew everything about everything regarding the wiring. PM me if you want his number, chances are he built your loom if it is from Ram.
The only other thing I can offer is the notes that came with the loom. They are comprehensive in listing where every wire starts and finishes, and is to BS standards, if your loom is not to BS standard then it will be no help.
So bon chance.

ps. re-check your earths, also if you have them, check the relays, AFAIK the lights should be on one spur. If too much current is flowing then I would guess a live is being earthed somewhere so check the switches too.

queeniee
31-08-10, 06:51 PM
Hi Queenie,
been away so just picked this up.
I know this may sound dull, but the first thing I would do is follow the wires and check for the obvious.
I had a fault which turned out to be the fog light. I had thought it would not matter which was live and which was return, little knowing the return was also earthed by one of the mounting screws! So I was earthing a live.
The thing is a fault like that can do things like slow the fuel pump if it drains current, so it often seems like a dark science!
Have you added or changed anything electrical recently (seemingly unrelated).

I had a loom built to suit the Ram from Thunder road. It was nearly perfect, and the chap who built it knew everything about everything regarding the wiring. PM me if you want his number, chances are he built your loom if it is from Ram.
The only other thing I can offer is the notes that came with the loom. They are comprehensive in listing where every wire starts and finishes, and is to BS standards, if your loom is not to BS standard then it will be no help.
So bon chance.

ps. re-check your earths, also if you have them, check the relays, AFAIK the lights should be on one spur. If too much current is flowing then I would guess a live is being earthed somewhere so check the switches too.
I changed nothing since last year, the only special event is that my car has not been used for 6 months due to an engine overhaul.
After days of research, I found the guilty wire: it was a bare one running close to the hood hinges. Vibrations destroyed partly the insulator over the wire.
I found on Internet the BS for wiring code and my Ram does follows this pattern closely. I also observed that the loom is similar to the one used on MGA. Now, after cleaning all the contacts including the fuse box, after some soldering and isolating wires, everything works fine and I can drive at night!!! Thanks to everybody for answers.
I shall send you a PM in case I need a complete loom later on.

wilf
31-08-10, 06:53 PM
Queenie - what you need to do to avoid this problem in the future is to take out your engine and give it to me, and fit something less vibratory - maybe a Wankel? :p