Irony
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| posted on 14/7/15 at 07:42 AM |
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Help! Electrical Gremlin Pre IVA - SOLVED
The electrics in my car were absolutely fine. Everything was running as it should. At some point a fault has developed. When you indicate left the
reversing lamp telltale flashes with the indicator. I have a reversing light switch on the dash which is okay for IVA.
 
Description
Here is my reversing lamp wiring diagram.
My first thought was a bad earth, I have heard these can produce random results. I have been over all the earth points (cleaned with sand paper and
put back) and I did find a loose one but it did'n't change anything. When I disconnected the main dash earth the reverse worked fine but
when it was reconnected it produced the same results. Also when the reverse lamp is switched on the rear side lights faintly glow.
As the telltale is a LED it can only work one way round. The power cannot be coming from the switch as the switch is off (tried a new switch, same
result). So the power must be coming from the reversing lamp side. However the reversing lamp is just a single simple wire that runs from the switch
to the lamp on the back for the car itself. I don't see how this can getting power from somewhere????
Anyone have any suggestions??? Oh and my IVA is in 3 weeks!!!
[Edited on 14/7/15 by Irony]
[Edited on 15/7/15 by Irony]
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minitici
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| posted on 14/7/15 at 07:53 AM |
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If that is all that is connected to the reversing lamp then there must be a bad earth somewhere.
You could fit a diode between the reverse lamp and the tell-tale that would stop any power being fed back via the reversing lamp earth.
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adithorp
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| posted on 14/7/15 at 07:54 AM |
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I know you've checked but it sounds like a bad earth on the indicator. Check again.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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Irony
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| posted on 14/7/15 at 08:03 AM |
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quote:
Originally posted by adithorp
I know you've checked but it sounds like a bad earth on the indicator. Check again.
I will check again but I just don't see how a bad earth can provide power where they shouldn't be power. The reversing lamp earth goes
back to the main earth point at the rear of the car. All of the rear lights go back to this one point so if it is bad then it could explain the
glowing tail lights. I have had this earth point off and cleaned and put back on.
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adithorp
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| posted on 14/7/15 at 09:18 AM |
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If the current from the bulb to earth can't reach earth it back feeds up any other circuits until it finds earth. What you describe are typical
symptoms of this.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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gremlin1234
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| posted on 14/7/15 at 09:29 AM |
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I agree it will be an earth fault, between the common connection of [ reversing light earth, and the Left indicator earth ], and that point back to
battery earth.
I would test this using a wire from batt earth to your rear earthing point.
(short answer, I suspect your common earthing point at the back is not as well earthed as it should be.)
edit:
if you really want to bodge it, replace the led with a real bulb. - the fault will still be there, but you wont see it!
[Edited on 14/7/15 by gremlin1234]
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Irony
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| posted on 14/7/15 at 10:29 AM |
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quote:
Originally posted by gremlin1234
I agree it will be an earth fault, between the common connection of [ reversing light earth, and the Left indicator earth ], and that point back to
battery earth.
I would test this using a wire from batt earth to your rear earthing point.
(short answer, I suspect your common earthing point at the back is not as well earthed as it should be.)
Simple enough to do. I'll unbolt the earth point and set up a temporary wire straight to the battery. If that cures it I know its the earth
point. If that doesn't work I'll have to split the earth point up and try them independantly of each other.
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gremlin1234
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| posted on 14/7/15 at 10:56 AM |
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quote:
Simple enough to do. I'll unbolt the earth point and set up a temporary wire straight to the battery. If that cures it I know its the
earth point. If that doesn't work I'll have to split the earth point up and try them independantly of each other.
you don't
even need to unbolt the earth first.
just connecting a explicit earth to the various points should show where the fault lies.
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RichN
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| posted on 14/7/15 at 06:15 PM |
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What diode would peeps recommend for stopping the current flowing in the "wrong" direction?
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gremlin1234
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| posted on 14/7/15 at 08:57 PM |
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quote:
Originally posted by RichN
What diode would peeps recommend for stopping the current flowing in the "wrong" direction?
if you think diodes are required**,
then a relay or 2 is probably better.
diodes are not a 'cure' for earthing problems.
**(alternators excepted! )
ps nearly typed earthling problems, I blame Marvin.
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02GF74
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| posted on 14/7/15 at 09:11 PM |
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If the revsrse switch is open, there is no way the tell tale can be fed with power to make it flash.
.... unless the gound at reverse lamp is not earthed but somehow getting power or same for reverse switch,
Is the led fitted correct way?
Is tell tale normal brightnezz?
Does it flash when gear is in reverse?
Happens for left and right indicatir?
Happens for hazard?
Any change when other lampz are on?
Any difference if engine running i.e. alternator charging?,
You need add indiator circuit wiring to the diagram coz theres nothing wrong with what you have.
[Edited on 14/7/15 by 02GF74]
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Irony
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| posted on 15/7/15 at 07:32 AM |
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I have sorted the problem (I hope). I started by taking apart the main earthing point at the back of the car. I checked to see where each earth went
to, light cluster, fog, reverse, etc etc. I found all of the lights missing on the offending side. On the original loom that came with car there are
several earth wires at the rear that go together to a OEM sealed crimp. I cut this off expecting to find all the lights on the left side earth points
and one larger wire going down the transmission tunnel to the dash earth. I did find that except the main wire that runs down the transmission tunnel
doesn't seem to appear at the dash end. What happens to it in the tunnel I don't know.
So it turns out that the rear left lights including Reverse and Reg Lamp were not earthed at all. How they were getting earthed I don't know.
I think maybe that when you indicated left power was running back through the reverse lamp down to the dash and through the LED telltale to earth.
This is bad!
See the actual wiring diagram
 
Description
This is simplified as all the nearside rear lights were earthing I think through the telltale on the dash! I can't understand why it seemed to
work before. Unless the mystery wire was earthed in the transmission tunnel somewhere and this earth has been knocked when I put the transmission
tunnel panels on. I can't access the tunnel with lifting the car up with the engine crane.
[Edited on 15/7/15 by Irony]
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HowardB
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| posted on 15/7/15 at 07:46 AM |
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yay,... live and learn.... locostbuilders rock!
good luck for the iva
Howard
Fisher Fury was 2000 Zetec - now a 1600 (it Lives again and goes zoom)
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adithorp
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| posted on 15/7/15 at 09:38 AM |
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So your earth wasn't connected....
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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Irony
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| posted on 15/7/15 at 12:13 PM |
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quote:
Originally posted by adithorp
So your earth wasn't connected....
If you want to make me sound like a thicko, then yes.
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adithorp
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| posted on 15/7/15 at 12:29 PM |
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Sorry, wasn't my intention. Was just confused that they were connected to a lead going back into the loom as it's normal to connect the
earths at the rear to the chassis there.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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Irony
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| posted on 15/7/15 at 01:06 PM |
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quote:
Originally posted by adithorp
Sorry, wasn't my intention. Was just confused that they were connected to a lead going back into the loom as it's normal to connect the
earths at the rear to the chassis there.
I don't know why the original Luego loom had the right side earthed at the back and the left at the dash. Makes no sense. I must have missed
it when installing the lights at the rear. I was sure the lights were working correctly before but maybe I missed that as well. I probably saw the
unused earth in the centre of the loom and capped it off because I thought everything was working. Bit scary that all the current was going through
the tiny LED wiring.
I have come across several items in my build where I have left something part finished because it was getting late etc. The following day I have
started another job and completely forgotten to finish the first job. For my next build I think a big white board on the wall and notes would help.
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