Lotus Elan

Complete electrical shut down....

PostPost by: Rogerg_268 » Tue Nov 21, 2017 5:02 pm

So my '69 S4SE Federal spec Elan has developed a worrying trait. A complete electrical shut down. No electrical power, no ignition lights, no starter - completely dead. The first time this happened I was driving the car for around 4miles and everything switched off (always interesting...). 5 or so minutes later it came back to life and then after leaving the car idling again for 10mins, it died again. So i suspect some kind of electrical overheating / thermal cut out. Car has an alternator.

Background; the car had recently had had the tacho converted to run electronic ignition. Previous to this the tacho was inoperable but no electrical cut outs and it always ran OK. I sent the tacho to be converted by Nisonger and followed their instructions and tacho now works fine. I have also noticed that the Voltage gauge rather than reading 13V or so, was now around 11V. Other oddities include running lights and indictors lights always on regardless of key / switch position (probably a bad earth and unrelated)

I discovered a loose connection in the fusebox and duly replaced but no change - switched off on the drive way after 10mins of idling. I did notice that the electrical cooling fan kept running so that is pulling 12v from another source to the other 12v systems.

Could it be the voltage regulator or is there something else that could overheat and cause the shutdown? As far as I know the only electric mods I made in fitting the tacho were the extra wire from the coil to the tacho and finding 12v power for it (could be this but it did appear to be an instrument feed...).

The general state of the wiring behind the dash is a little horrifying but all appears to be connected.

Any thoughts from the Elan electrical guru's would be appreciated.
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PostPost by: nmauduit » Tue Nov 21, 2017 6:10 pm

have you checked that the fuse itself is tightly held in place? I had the problem of an intermittent shut down because the fuse holder had lost its springiness...
- have reread your post it seems that a short may be also to consider (voltage drop, lights on - behind the dash is not unlikely)... good luck !
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PostPost by: bob_rich » Tue Nov 21, 2017 8:20 pm

HI

A complete electrical shut down suggests the battery is disconnected. But if it is a complete shut down then the generator may not be operational leaving the battery to provide all the power. then a poor battery connection lets go
and the whole system shuts down as you have had.

check the battery connection especially the earth terminal in the boot. then when it runs check that the alternator is charging the battery. A test meter on the battery should read around 12.5V with everything off then after starting it and holding around 2000 to 300rpm engine speed should rise to around 14V but if it sits around the 12.5V level then the generator is not charging.

hope this helps best of luck

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PostPost by: pharriso » Tue Nov 21, 2017 11:20 pm

bob_rich wrote:HI

A complete electrical shut down suggests the battery is disconnected. But if it is a complete shut down then the generator may not be operational leaving the battery to provide all the power. then a poor battery connection lets go
and the whole system shuts down as you have had.
Bob


+1
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PostPost by: gjz30075 » Wed Nov 22, 2017 9:53 am

Rogerg_268 wrote: Car has an alternator.

.


Check the big brown wire on the alternator lug and follow it back. May be a loose connection there.
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PostPost by: nmauduit » Wed Nov 22, 2017 10:39 am

Rogerg_268 wrote:Other oddities include running lights and indictors lights always on regardless of key / switch position (probably a bad earth and unrelated)


rereading again (...) I'm always suspicious of unrelated problems that would occur simultaneously : did these other oddities occur recently ? the key switch is quite crammed behind the dash and can be subject to issues (erroneous wiring, internal shorts...), maybe worth checking ... one thing that can happen when working on the dash is creating shorts or opens because of the little room for the harness.

Regarding the diagnosis : is the shutdown absolutely complete when it occurs (no light anywhere including interior dash etc, no trace or voltage anywhere)? if so you should be able to trace the default coming from the battery as suggested above, and if the intermittent default appears just when idling it should not be too difficult to recreate the default condition for narrowing it down...

Apart within the alternator if non stock I'm not aware of the existence of a "thermal cutout" on a federal s4 - at least engineered as such - so as suggested above you may want to double trace and check the wiring linking battery and alternator, and also (with a glove) checking if something is actually hot (alternator ?) when the shutdown occurs.

good luck !
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PostPost by: Chancer » Wed Nov 22, 2017 11:45 am

If the vehicle has an alternator and assuming that it is functioning then a battery disconnection while the engine is running would have absolutely zero effect on the electrical system. In addition to that any dodgy connection would manifect itself in the starter not operating, all the other electrical loads are minimal in comparison.

Could a malfunction of the anti-theft switch cause this problem, maybe something rolling around in the glove box? I have not re-read carefully the OP's description so ignore it if its not possible.
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PostPost by: gus » Wed Nov 22, 2017 12:34 pm

The fan continues to run?

Check where it is connected that is the last place you can prove power.

I suspect a connection in the fusebox
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PostPost by: billwill » Wed Nov 22, 2017 5:06 pm

Chancer wrote:If the vehicle has an alternator and assuming that it is functioning then a battery disconnection while the engine is running would have absolutely zero effect on the electrical system. In addition to that any dodgy connection would manifect itself in the starter not operating, all the other electrical loads are minimal in comparison.

.



>a battery disconnection while the engine is running would have absolutely zero effect on the electrical system

Except possibly to damage the alternator's electronics!
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PostPost by: Chancer » Wed Nov 22, 2017 7:18 pm

Yes thought of that after posting, theoretically could do so but back in the day I must have swopped batteries after a vehicles engine was running scores of times without incident.
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