Lotus Elan

Popping fuse

PostPost by: Dave Fowler » Fri Jun 25, 2010 1:29 pm

gerrym wrote:Dave, does your S130 have the 4 fuses in the dashboard, behind the removeable wooden cover? Are they connected. If so, the wiring should be at least roughly as per the S130 wiring diagram shown in the manual. Also, how many relays do you have ? just the horn

If you have multiple relays under the bonnet, close to the wiper motor, your S130 may be wired up as a Plus 2S. Also do you have an Alternator, another good pointer

My car, 1972 so badged as an S130, started life wired up loosely as an Plus 2S. After the under dash fire, the previous owner had it re-wired as an S130 (ie no relays).

Regards

Gerry


Yes, that's definitely it! I'd been wondering why the diagram for the Plus 2S in the manual looked so much more like my car than the S130 - and now I know. I can confirm that I have an ashtray in the middle of the dash, and that there are several relays under the bonnet by the fuses.

This doesn't resolve the fuse-blowing issue I have, of course, but knowing the wiring model I have will certainly make life easier. My car seems to have wires of different colours, so that should also make things a little simpler.
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PostPost by: persiflage » Sat Jun 26, 2010 12:53 pm

Robbie.
you asked
I'd like to put some additional protection in too but my useless electrical knowledge is causing me trouble grasping this! So, if I were to put additional fuses in at the start of the main circuits as Dave intends, where would they physically go?


Depends whether you want "function" or "function and form" :)

I have a battery c/o switch which is a must! As I wanted the c/o to act as a safety + anti theft device I have it hidden away high and forward in the passenger foot well. This leaves me with several feet of unprotected battery cable which I should do some thing about, but back to the fuses.

I replaced the original :oops: "tin can" headlamp relays with modern fused relays attached to the bulkhead where the control box used to be. This leaves a minimal amount of un-fused headlamp power cable coming from the alternator connector. A main power fuse could be wired into the output from the alternator in the same area. This would of course need to be of sufficient rating to to accommodate all services. My belts & braces safety fuse is currently inside the car where the main brown feed enters (fitted as an after thought :oops: ) and I can confirm that a 25A fuse allows me to operate the car but also provides excellent protection against a short. Not pretty, but functional.
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PostPost by: gerrym » Sat Jun 26, 2010 2:00 pm

Persiflage, I think your approach is sound and most owners do not want to loose their cars due to an electrical fire, even if the required mods are strictly non original.

The main lead from the battery can easily be protected by a fusible link (Auto Electrical supplies retail suitable holders and the fusible link itself). In essence these are just a large bolt-in-place fuses.

Protecting other wires that feed large currents needs to be based on the maximum current that the wire can safety handle. It's a good idea to remove the heavy currents from behind the dash for the headlights and electric windows. These should be fed direct via fuses and the relays with fuses are an excellent way of doing this. Just be aware that modern relays with small air gaps need some circuitry to prevent contacts from welding, while also quenching the high voltages (probably more than 200V) which are generated from the back emf.

Last thing on this is that because the earth routes are generally longer than with a metal bodied car, earth cables need especial care that they are adequately sized for the current that they carry.

Regards
Gerry
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PostPost by: Dave Fowler » Sat Jun 26, 2010 6:15 pm

Well, in this instance I'm pretty sure I've found my culprit - and it's the engine cooling fan. I just thought I'd check a few things and my suspicions moved in that direction; then, when I cut out the thermal switch at the top of the radiator and turned on the ignition, pop went the fuse. Not that this invalidates all the good advice I've received from this thread - I'll most definitely be checking behind the dash before too long to see what it's like in there.

Now, it may simply be that I need a bigger fuse than I've tried in that position, but I think that's unlikely, as I've gone as high as 20 amp thus far. But I'll check out the manual and see (I'm at my girlfriend's at the moment and said manual's at my house). If it is the fan, I guess I'll need to get hold of a new one, as I can't see that the thing's easy to get apart (and I wouldn't really know what to do with it if I did get it apart).

Any ideas on fuse capacity in that position?
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PostPost by: billwill » Sat Jun 26, 2010 6:32 pm

It may be that the fan is seized up & will be ok after you free it up.

While seized it will consume lots more current than normal.
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PostPost by: gerrym » Sat Jun 26, 2010 7:38 pm

Dave, Bill is probably correct with the fan being seized. In any casetest the motor by providing a direct feed to the fan motor (ie bypass the wiring) and see if it spins up and runs quietly. If it runs OK, you might want to consider running a relay for the fan. Then the circuit through the fuse only needs to handle the switching load for the relay. You can keep the fuse small and therefore protect the other smaller wires on the same fuse circuit.

On the question of running a full 20A current through the wiring, just consider that a bad connection of say 0.05 ohms will generate 20W of heat (at nominal voltage) for a 20A current. 20W of heat will start a fire if there is no heat dissipation (just think of a small soldering iron and the damage that can do). That 0.05 ohm bad connection would probably never be noticed for something like a fan as it would only cause 1V of voltage drop.

Regards

Gerry



.
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PostPost by: Dave Fowler » Sat Jun 26, 2010 10:30 pm

billwill wrote:It may be that the fan is seized up & will be ok after you free it up.

While seized it will consume lots more current than normal.


The fan turns when I push the blades round, so I guess it isn't seized. That said, I haven't tried it again after removing, spinning and replacing it, so I'll give that another go. I'll also try a direct connection, as per Gerry's suggestion.
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PostPost by: persiflage » Mon Jun 28, 2010 4:05 pm

Gerry,
Back emf ? I haven?t given much thought to that since I was studying for my tickets!
My thinking was that if the relays were good enough for modern cars, they should be ok for the Elan.
The belts & braces fuse is less about protecting the wiring and more about protecting the car. The wiring can always be replaced with time, effort and money. The car is a different prospect. Without a fundamental redesign of the switching and wiring I thought that a 4 fuse block along with the fused h/l relays and the b&b fuse (total 7) was a reasonable compromise when compared to the original 2x35amps.

Dave,
Don?t be fooled by the fan rotating ? it could be the wiring inside. A simple/practical method to further evaluate the problem would be to disconnect the fan and then sort the temp. sensor. Do the fuses continue to blow?
Are you using glass envelope fuses, can you see the link? A short will cause the fuse to blow immediately, if you have an overload situation the time taken to blow could (from experience) be typically 2 ? 5 seconds.

I have measured current draw for various items, at the fuse block.
Rev. lts. 3A
Wiper 3.8A
Washer 0.9A
Fan htr 4.5A
HRW 0.3A
Inds 3.2A
Stop lts 3A
Fan rad 2.6A
Air horn 10+ A :o

The value for the horn compressor was a surprise.

As I get older, I find myself concerned about the shortcomings of the Elan wiring, yes...
but more concerned about the sparky, heavy duty rotating thing and the lighter duty sparky things directly under the fuel distribution device. The slightest smell of petrol makes me twitchy!
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PostPost by: gerrym » Mon Jun 28, 2010 4:36 pm

Flage (if that's your name?), good data for the current draw. The motors will of course have an inrush current several times greater than steady running.

The point about protecting the wiring is of course not so much to protect the wiring itself (as you say that can be replaced), but to prevent fires. Fires are a definite thing to avoid in an Elan, whether electrical or petrol assisted.

Relays in a modern installation will normally have something to clamp the maximum voltage (eg a varistor).

Regards
Gerry
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PostPost by: Dave Fowler » Mon Jun 28, 2010 5:05 pm

persiflage wrote:Dave,
Don?t be fooled by the fan rotating ? it could be the wiring inside. A simple/practical method to further evaluate the problem would be to disconnect the fan and then sort the temp. sensor. Do the fuses continue to blow?
Are you using glass envelope fuses, can you see the link? A short will cause the fuse to blow immediately, if you have an overload situation the time taken to blow could (from experience) be typically 2 ? 5 seconds.

I have measured current draw for various items, at the fuse block.
Rev. lts. 3A
Wiper 3.8A
Washer 0.9A
Fan htr 4.5A
HRW 0.3A
Inds 3.2A
Stop lts 3A
Fan rad 2.6A
Air horn 10+ A :o

The value for the horn compressor was a surprise.

As I get older, I find myself concerned about the shortcomings of the Elan wiring, yes...
but more concerned about the sparky, heavy duty rotating thing and the lighter duty sparky things directly under the fuel distribution device. The slightest smell of petrol makes me twitchy!


I've tried out the fan in situ by wiring directly to it and then to earth with the car's own wiring disconnected, as per Gerry's suggestion above - turned on ignition, 15A fuse blew pretty much immediately. I then removed the fan and tried connecting it directly to a spare battery - it did turn, but there was a lot of sparking and the wires I was using heated up no little. So it looks like overload, and enough of one to ping the fuse in no time flat. Looking at the unit and bearing in mind its likely age, I decided against trying to fix it.

So, I now have a nice new Kenlowe unit winging its way to me; hopefully I'll have it by Wednesday morning, then I can fit it in the evening. As I don't really need a car tomorrow or Wednesday, but I pretty certainly will on Thursday (my everyday car is currently having a recalcitrant pattern panel forced into something approaching the correct shape - a common experience with 2CVs these days), this will be just fine and dandy.

I know what you mean about the distributor's proximity to the carbs - not the smartest arrangement.
1972 Plus 2 S130
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PostPost by: bob_rich » Mon Jun 28, 2010 5:37 pm

Hi

In an earlier post link below I posted some info on the fuses in my car.

I agree with the other post that the fuses are quite high values for the wiring and am planning on my rebuild to put in modern fuses and more of them to look after the wiring

hope this helps best of luck

Bob

elan-plus-f13/electrics-t18977.html
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PostPost by: gerrym » Mon Jun 28, 2010 5:58 pm

Dave, I'm glad collectively we could help you, in the usual roundabout Lotus way.

I always think there is a nice symmetry to a post, if the originator posts the final thoughts, and no one else jumps in with their own little coda.

So over to you Dave

Regards
Gerry
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PostPost by: Dave Fowler » Mon Jun 28, 2010 6:25 pm

gerrym wrote:Dave, I'm glad collectively we could help you, in the usual roundabout Lotus way.

I always think there is a nice symmetry to a post, if the originator posts the final thoughts, and no one else jumps in with their own little coda.

So over to you Dave

Regards
Gerry


Gerry, that's very nicely put - and I agree entirely. Thanks again to one and all for your thoughts and help; having got to the bottom of my original problem I have also collected some very useful knowledge and advice on Elan electrics. So before too long I'll have a good look behind the dash to see what lurks there - in fact, I think I'll need to do that to find out why the directional control for hot/cold air seems to have no effect whatsoever! But that's another story - and another potential thread on here...
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