Lotus Elan

Chasing Ground issues on S3

PostPost by: pcarew » Fri Dec 27, 2019 9:56 pm

The Lotus Workshop manual states That the wiring loom is earthed at three points:
1) Front engine bay (Left front chassis upright, close to radiator)
2) Facia/Dash. Left hand Facia/Chassis mounting bolt
3) Rear Boot/Trunk Chassis mounting bolt.

I have identified and cleaned 1 & 2, but I haven't seen where my Loom would connect at the Dash. There doesn't seem to be any spare/dangling earth wires that are coming out of the loom and the Chassis bolts only have the Heater earth connected to them.

Can others confirm that there is indeed a grounding point for the wiring harness/loom at the dash chassis bolt?

If so, where in the harness does the grounding wire connect with the other black ground wires?

Any photos?


Cheers
Paul.
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1967 Lotus Elan S3SE Right Hand Drive, FHC 36/7152 BOO 758F
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PostPost by: Alasdair » Sat Dec 28, 2019 3:51 pm

Paul,

There should be a black ground wire that is attached to the bottom left side of the dash through a plate that holds the bottom dash, the bolts are fastened to the chassis through the plate. My Elan?s are LHD, not sure if a RHD car would have the wire attached to the RHS of the dash??

Regards,
Alasdair.

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PostPost by: pcarew » Sat Dec 28, 2019 5:38 pm

Hello Alasdair,
Thanks for replying.
Do you know where that black ground connects up in the wiring harness by any chance?

My harness doesn't have one, so I'll have to add one in

Paul
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PostPost by: RogerFrench » Sat Dec 28, 2019 6:41 pm

You might first check that the wire that is supposed to connect to the ground hasn't been used to provide grounding for something else. Do you have any additional non-standard accessories? If so, how are they grounded?
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PostPost by: pcarew » Mon Dec 30, 2019 4:35 pm

Hello Roger,
Good point and worth checking.
I don't have any non standard items on the dash.

I guess I can daisy chain a ground to the chassis bolt from an existing ground, but I'd rather have a separate/ dedicated line from the wiring harness
Paul Carew
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1967 Lotus Elan S3SE Right Hand Drive, FHC 36/7152 BOO 758F
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PostPost by: LI-599 » Mon Dec 30, 2019 10:00 pm

Hi Paul, it is a few years since I connected all the wiring behind the dash, but I am fairly sure there was no ground wire in the loom, just a collection of ground wires connecting to the bolt behind the lower left corner of the dash that screws into the chassis/ frame.
Ian
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PostPost by: pcarew » Tue Dec 31, 2019 12:10 am

>"... I am fairly sure there was no ground wire in the loom, just a collection of ground wires connecting to the bolt behind the lower left corner of the dash"

Hmm, interesting. My grounds from the instruments etc, disappear into the loom.

It is possible that this is a replacement wiring loom. Back in the late 80's, I had smoke coming from behind the dash and the garage that 'fixed' it, may well have put in a new wiring loom. It's a long time ago now and I don't recall what the resolution was.

I'll dig a little deeper, thanks
Paul Carew
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1967 Lotus Elan S3SE Right Hand Drive, FHC 36/7152 BOO 758F
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PostPost by: LI-599 » Wed Jan 01, 2020 4:51 am

Oops, sorry yes there are some ground wires in the loom which end up at the above mentioned bolt.
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PostPost by: el-saturn » Wed Jan 01, 2020 9:00 am

PLUS: ------------------ as nobody looks under your dash and assuming you're creative: just use one of the many black cables (make both ends match = current passage) and use the MAIN ground bolts - front or rear. maybe i'll get contradicted? sandy
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PostPost by: lotusbzz » Sun Jan 19, 2020 3:28 pm

Hallo!
I wired a 6 mm black ground wire directly from the Negative of the battery through the left sill to the fixing plate of the dashboard through the left sill
it grounds all the button/instruments assembly .
It's not original but help to solve gramling related with the bad grounding.
I hate to open that silly dashboard .
Paolo
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PostPost by: ericbushby » Sun Jan 19, 2020 4:23 pm

Hi Paolo,
Running an extra earth wire to the battery can sometimes cause problems.
I suggest that you disconnect your new negative wire at the battery end and check that it is not accidently still connected to the chassis anywhere at the front end.
If the main battery earth or chassis connection becomes loose or corroded, then the starter motor current will flow down your new wiring and cause overheating.
It may be better to connect to the chassis at the front and not to the battery to avoid problems.
I expect you have thought of this and have done it carefully, but some simple things are easy to miss.
Just trying to help
Regards
Eric in Burnley
1967 S3SE DHC
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PostPost by: lotusbzz » Sun Jan 19, 2020 6:18 pm

You are right!
Will do it soon
Thanks
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