25 Amp fuse blowing

[pereirac]

My Elan's been pretty reliable but the other day when I tried to start her she blew the lower 25Amp fuse. I replaced it and the fuse blew straight away again, so it looks like there is a short somewhere? I seem to remember this happening a while ago but can't remember what was up? I have electronic ignition (Lucas unit) but apart from that most of the parts are as original. All suggestions welcome.

Thanks

Carl

[elansprint71]

Fit a 5mm dia bolt instead of a fuse; this should lead you straight to the problem. Perhaps pre-booking the fire brigade would be wise if you live in a country area.

Well, you did ask for "all" suggestions.


I would look at all the bits and pieces which that fuse protects for signs of something shorting out. If you can't see anything obvious, disconnect things to eliminate the suspects. Good luck- Lucas, eh.

[Frank Howard]

Carl,

I thought the original Lucas fuse box took two 35 amp fuses.

[1964 S1]

Hi Carl, Are you saying the car won't start?
If you replace the fuse and turn the ignition on to the first click, will your turn signals work?
Eric

[pereirac]

Thanks for all the comments. Elansprint71, I assume you are hoping the the other Sprints catch fire leaving just yours? Although a bolt when I ran out of fuses was tempting...

It's quite a search to find out what size fuse the Elan takes, the owners handbook does not give the size and it's pretty well hidden in the factory manual. I finally found it in the parts list and yes it is 35 Amps, but as my car seems to be happy with 25Amps (until recently) I will stick with the lower rated fuse in the hope that this will stop the car catching fire.....

It looked like the problem was caused by a short in the horn circuit (somewhere). It's the secret switch in the glove box which was causing the fuse to blow when the engine was turned over. It's supposed to sound the horn but in my case it just blew the fuse (an even better anit-theft device).

Next weekends project then to find the short in the horn circuit. In the meantime I will keep the horn disconnected, the roof down and just shout!!

Carl

[ppnelan]

I believe a horn can take enough current to blow a 35A fuse. I read (somewhere...) that you should remove the fuse & replace it with e.g. a 5mm bolt ( ) IF you need to operate the horn for a 'long time' - why you'd need to do this I do not know - to test it (long-term reliability?!) perhaps
Anyway, it sounds like yours may be stuck if it is a compressor-operated air horn, drawing too much current.
Don't forget that a 35A fuse will 'only' carry 17.5A and blow at 35A (but what happens between 17.5A & 35A...?!)...

Matthew

[steveww]

It is a good modification to rewire the horn so that it uses a relay and a separate fuse.

I have done this and thus the main fuse box only needs a pair of 8 amp fuses.

[Frank Howard]

the main fuse box only needs a pair of 8 amp fuses.

Steve,

Really? Try backing up the car with the direction signal on. If that doesn't blow one of your 8 amp fuses, add the cigar lighter and/or the wipers. I realize you said 8 amp, but I know from personal experience that a 5 amp fuse will not support the wipers and washers together.

[ianf]

Carl,

I had a blowing fuse which meant the horn wouldn't work. I could only see that the cigar lighter was protected by the same fuse but I established that this wasn't the problem. On a long drive back from Dijon last summer I had plenty of time to think it through and I realised that the problem was more prevalent in the summer. Coincidentally the fan wasn't switching on by itself either! The problem was a short in the electric fan circuit which of course made the problem infuriatingly intermittent!

Hope this helps.

Ian

[steveww]

the main fuse box only needs a pair of 8 amp fuses.

Steve,

Really? Try backing up the car with the direction signal on. If that doesn't blow one of your 8 amp fuses, add the cigar lighter and/or the wipers. I realize you said 8 amp, but I know from personal experience that a 5 amp fuse will not support the wipers and washers together.

Never tried doing that but in my regular use the 8 amp has never blown. The horn and rad fan are on separate relay circuits with their own fuses. As I don't smoke I have never used the cigar lighter. I also tend to only use the Elan in the sun shire with the roof down, no need for wipers.

[alexblack13]

Never tried doing that but in my regular use the 8 amp has never blown. The horn and rad fan are on separate relay circuits with their own fuses. As I don't smoke I have never used the cigar lighter. I also tend to only use the Elan in the sun shire with the roof down, no need for wipers.


Oh you shoodny have said that laddie..It will now rain for ever n ever....



Alex B...

[elansprint71]

If your car is fitted with air-horns they do draw quite a current (even when new and in good condition) but I would have thought that, if they were the problem, then the fuse would blow at the same time as the horns did not.
I co-existed with the worst looking Elan wiring loom in the world for five years (everything worked but no-one knew how/why) before bighting the bullet(s) and fitting one of Paul Matty's custom-made looms (if anyone can tell me for which car these things were custom-made, I would be obliged, because it certainly was not a Lotus Elan).

Since then everything has worked perfec............ no, I'm not going to say it.

[pereirac]

I actually have a new Paul Matty wiring loom (I changed it when I rebuilt the car). Very nice but one problem, it seems to have connections in for evey option, including thoses not fitted to my car ... So I have twice as many connections as I need.. Well it feels like twice, but I suppose lost of spare wires should I need them...

Carl

[wojeepster]

instead of fitting a bolt which can start everything on fire if you have a fuse that keeps blowing you can fit a resetting circuit breaker or two prong flasher. It will keep clicking away while you play with the wiring until you find the bad spot. You can also use a short finder to find the location of the problem. Search short finder on fleabay.

[dlbutler]

Even better than a circuit breaker or a flasher is a light bulb. When the light goes out the short is found.

Don