Lotus Elan

Popping fuse

PostPost by: Dave Fowler » Wed Jun 23, 2010 8:37 am

Morning all,

My Plus 2 has the rather irritating habit of blowing the fuse which feeds the wipers, washer and heater fan. It just seems to happen as I'm driving, rather than when I actually use any of those items. So naturally, I'm thinking there must be a short somewhere. According to my newly-obtained workshop manual, the same fuse also feeds the cigarette lighter (the one item on the car I can guarantee I'll never use!) - so it seems to me that this is the most likely cause of any shorting. For the time being I'll just leave the lighter bit out of its socket and see what happens.

However, the manual doesn't give any information as to what rating all the fuses should be, and the owner's handbook doesn't even mention fuses! Does anybody know where I can get my hands on this information? And am I on the right lines with my suspicion of the lighter?

Many thanks in advance,

Dave
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PostPost by: gerrym » Wed Jun 23, 2010 9:30 am

Dave, have you had a look at the wiring behind the dashboard. If its in a bad state, then this might be the cause of your problems. I'd be very wary and super vigilant to isolate the battery whenever you leave the car. Also carry a fire extinguisher and have it in a handy location. I know all this stuff because my Plus 2 S130 had a small electrical fire behind the dash.

Please note that the function of a fuse is to protect wiring, not a component. The layout of the Lotus Factory Plus2S130 wiring spectacularly fails to provide this protection because the opportunities for shorts are upstream of the fuse locations. Therefore large currents can flow in small wires which leads to the insulation melting and catching fire.

I'd have a chat with an auto-electrician and see what they can do to improve the protection. (Once you have looked behind the dash you may decide on a full rewire).

Regards
Gerry
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PostPost by: types26/36 » Wed Jun 23, 2010 9:56 am

I once had a similar problem with a Plus Two, it would blow a fuse at random while driving, I eventually found the wire leading down to the reverse light switch had chaffed through with movement of the engine/gearbox , it would short at various times and blow the fuse.
I don't know if the reverse fuse is on the same circuit as your problems but it may just be worth looking at.
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PostPost by: andyelan » Wed Jun 23, 2010 1:01 pm

Hi Everyone

The problem of reversing light switch which Brian talks of is most likley on Plus 2s fitted with the five speed gearbox. The switch is very close to the g/box cross member and the terminals can easily touch which is what happened to me a while ago.

Andy
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PostPost by: persiflage » Wed Jun 23, 2010 4:49 pm

The layout of the Lotus Factory Plus2S130 wiring spectacularly fails to provide this protection because the opportunities for shorts are upstream of the fuse locations. Therefore large currents can flow in small wires which leads to the insulation melting and catching fire.


Exactly the same with the little- uns.
After converting to Alternator power, I wired in a blade fuse holder reasonably early in the cct. Not a delicate sophisticated answer, but with sevices split between 4 fuses and fused H/L relays, certainly better protected than before. :D
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PostPost by: Dave Fowler » Thu Jun 24, 2010 6:04 am

gerrym wrote:Dave, have you had a look at the wiring behind the dashboard. If its in a bad state, then this might be the cause of your problems. I'd be very wary and super vigilant to isolate the battery whenever you leave the car. Also carry a fire extinguisher and have it in a handy location. I know all this stuff because my Plus 2 S130 had a small electrical fire behind the dash.

Please note that the function of a fuse is to protect wiring, not a component. The layout of the Lotus Factory Plus2S130 wiring spectacularly fails to provide this protection because the opportunities for shorts are upstream of the fuse locations. Therefore large currents can flow in small wires which leads to the insulation melting and catching fire.

I'd have a chat with an auto-electrician and see what they can do to improve the protection. (Once you have looked behind the dash you may decide on a full rewire).

Regards
Gerry


Thanks for the advice Gerry - I'll certainly have a look behind the dash! When you say upstream of the fuses, does this mean that the route the current takes is power supply - switches - fuses - electrical items? If so that's not at all healthy. In the case of my car, a fuse blowing must surely indicate that any short is in an area covered by said fuse, which is less scary. Not that it would mean that there's nothing nasty elsewhere, of course.

I know my car has been rebuilt, with few miles covered since said rebuild, but I don't have a great deal of info on the rebuild itself - so I don't know how much was done to the electrics on the car. I've been intending to contact previous owners if possible to get more info, so I'll make that a priority as well.

Dave
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PostPost by: gerrym » Thu Jun 24, 2010 6:13 pm

Dave, this reply is based on the wiring diagram in the workshop manual shown for a S130 non federal. I don't know whether its applicable to your car or if your car is wired differently.

The fuse 2nd from left in the diagram, takes its feed from the ignition switch Accessory terminal 5. It feeds +12V to heater motor, washer switch, windcreen wiper switch for fast and slow (note that the actual main feed switch to the windsceen motor is actually inside the motor) and engine cooling fan.

A different fuse, 1st from the left in the diagram, takes its feed from number 2 ignition switch terminal (ie is always live and is not switched). This feeds door warning lights, glove box light, cigar lighter, map light, horn relay, engine light under the bonnet, horn relay, horn, boot light nd window wiper motor main feed. The feed wire upstream of the fuse also powers the electric windows so no fuse protection. Large wires for these are routed behind the dash and therefore can provide a huge fault current and heat/fire source. I.e, a disaster waiting to happen.

So I guess the first thing to do is to check your diagram and/or find what has been fitted to your car. Otherwise you may just end up with a nasty problem.

Regards

Gerry
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PostPost by: kstrutt11 » Thu Jun 24, 2010 8:44 pm

Just spent ages trying to work out why brake lights and brake warning lights stopped working but other things that were supposed to be on the same fuses worked OK, as both the first 2 fuses have only green wires leaving then It looks like some of the wires are on the wrong fuses and the fault was one faulty fuse, lesson learnt, don't take the diagram as gospel!
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PostPost by: Dave Fowler » Thu Jun 24, 2010 9:03 pm

gerrym wrote:Dave, this reply is based on the wiring diagram in the workshop manual shown for a S130 non federal. I don't know whether its applicable to your car or if your car is wired differently.

The fuse 2nd from left in the diagram, takes its feed from the ignition switch Accessory terminal 5. It feeds +12V to heater motor, washer switch, windcreen wiper switch for fast and slow (note that the actual main feed switch to the windsceen motor is actually inside the motor) and engine cooling fan.

A different fuse, 1st from the left in the diagram, takes its feed from number 2 ignition switch terminal (ie is always live and is not switched). This feeds door warning lights, glove box light, cigar lighter, map light, horn relay, engine light under the bonnet, horn relay, horn, boot light nd window wiper motor main feed. The feed wire upstream of the fuse also powers the electric windows so no fuse protection. Large wires for these are routed behind the dash and therefore can provide a huge fault current and heat/fire source. I.e, a disaster waiting to happen.

So I guess the first thing to do is to check your diagram and/or find what has been fitted to your car. Otherwise you may just end up with a nasty problem.

Regards

Gerry


I got myself a workshop manual the other day, and I must confess I was puzzled by the wiring diagram for my car (as you rightly say, it's an S130 non-federal). Rather annoyingly, they seem to have changed the style at some point, making it less easy to understand. The actual diagram shows only four fuses, whereas the car has three boxes with four in each one. Mine also has an additional box with two fuses in it, one of which appears to have nothing connected either side. Elsewhere in the manual there's a diagram of all 12 fuses, but the engine fan's not even mentioned in that. All very confusing, and suggests that, as you say, the wiring generally is not brilliant. I may well follow the lead of an earlier poster on this thread and fit additional fuses at the start of the main circuits - the idea of heavy-duty wiring, always live, behind the dashboard isn't a pleasant one.

At least the manual has good instructions on removing the fascia - looks like that's a job I've got coming up very soon!

Again, thanks for the advice - it's much appreciated.

Dave
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PostPost by: billwill » Thu Jun 24, 2010 9:18 pm

The wiring diagrams were never ever much more than a rough indication of where the wires go.

:lol:
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PostPost by: gerrym » Fri Jun 25, 2010 5:52 am

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
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PostPost by: Robbie693 » Fri Jun 25, 2010 9:37 am

The early S130 models had the 'S' type loom, with all the fuses and relays under the bonnet. These models usually have the the ashtray in the dash, where the fuse box is on the later cars.

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?

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PostPost by: gerrym » Fri Jun 25, 2010 10:07 am

Robbie, sound very much like my car. The situation is made worse on some cars by the use of all white wiring (no colour coded) with tracers only.

Re fitting additional protection: I think the most pragmatic protection is a battery cuttoff switch which is always used. Then an extinguisher.

Beyond that, protecting the wires needs to work on the basis that all the connections including the earth connections need to be good, corrosion free and tight. Otherwise Ohms law gives you heat = current x resistance and if that heat at a bad connection is not dissipated, the insulation will melt and you will end up with a fire.

Next thing is to make sure that all the earths are good, because otherwise heavy current can flow down a secondary route, maybe a smaller wire, and again will cause it to overheat. Maybe that wire will then burn out or maybe it will smolder and set fire to another wire.

Beyond that, it's possibly a case of adding some fusible links (very high current fuse like things). But this can only really be done if you have back-drafted a circuit diagram to reflect the individual cars wiring. Otherwise it not possible to really know what good you are achieving or how to fix it in the future. I think at this stage, a lot of folks just elect to get the car re-wired from scratch.

One practicle step that would help most Plus 2 owners is to get all the wiring behind the dashboard changed so that it is semi-permanently attached to the dash and connected into the rest of the car by multi-connectors. This enables the wiring to be neatly and securely attached to the dash off the car, then installed and connected separately.

Regards
Gerry
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PostPost by: Robbie693 » Fri Jun 25, 2010 10:58 am

Thanks Gerry,

I do have a battery cut-off and use it religiously.

The car was rewired and still looks in good condition and I don't seem to have any electrical problems. I had the dash out last year and all the connections are good.

From what people were saying in the previous posts I was thinking they were refering to putting in some in-line fuses somewhere as backup for any problems that could emerge whilst driving. I am kind of familliar with the fuseable links you mentioned as there is one in the alternator circuit on our Mini but, as you say, it's difficult to know what good these would do. Particularly for me!

I knew someone who had a small fire behind the dash on his Plus 2 and that's what concerned me, but his car had been chopped about a fair bit and I don't think his wiring was in the best condition.

At least I have a fire extinguisher in the car should anything happen, although getting to the back of the dash before the car melted could be a bit fraught!

Thanks again

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PostPost by: gerrym » Fri Jun 25, 2010 11:43 am

Robbie, maybe the reason Lotus installed the fusebox in the dash on the S130, was because it provides a convenient extinguishing route to a wiring fire.
:)
Seems anecdotally that wiring fires behind the dash are not that unusual.

Regards
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