Lotus Elan

Faulty Ground?

PostPost by: chickenstock10k » Sun Jan 27, 2019 10:29 pm

Alright, working out the early ownership kinks on my Elan +2 and I?ve noticed some inconsistent electrical issues that seem to come and go. For example, the tach stops working and then 5 minutes later it will start working. They headlights will open and then turn on a few minutes later or sometime right away. As a new Lotus owner, I think I am dealing with a faulty ground somewhere. As a new fiberglass body car guy, feels like I am in virgin territory.

Is the best way to start troubleshoot to just clean up the major grounding points and reconnect?
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PostPost by: billmoore42 » Mon Jan 28, 2019 12:48 am

My 67 Elan FHC recently had headlights that starting turning off when driving. The vacuum headlight riser mechanism was working fine, but the lights started turning off in a random fashion. I finally started wiggling wires under the dash, and found when I wiggled the wires connected to the headlight relay, the lights were affected. Taking out the headlight relay (quite a job, as it is mounted on the firewall on my car at least buried under the dash) and wire brushing the spade contacts fixed the problem. Cleaning up the spade connectors to the headlight switch also would not hurt.

If the headlight relay is working, when you turn on the headlight switch, you should head an audible click coming from the relay.

Another thing to look at regarding the tach is the grounding wires connected to the back of the case. Remove this black wire and clean up the contact with a wire brush or something similar, and make sure the knurled nut that holds the black ground wire in place on the back of the gauge is tightened down securely.
1967 Lotus Elan FHC Spyder Chassis
1972 MGB (since 1975)
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PostPost by: Bigbaldybloke » Mon Jan 28, 2019 1:39 am

I?ve had various problems, things not working, handbrake light coming on when other things are switched on, the fuel gauge gradually rising as you are driving etc etc. Best advice is to go to each of the main earth points in turn, undo, clean and re tighten the connections, I use a smear of copper based grease on mine. There are several earth connections, starting with the main battery connection to the chassis in the boot, behind the dash on the lower left adjacent to the gear lever, to the front left suspension tower, across the engine mounting between chassis and engine for the starter motor main earth, between the oil pump and the ignition coil. Then there are earth connections behind the dash, where several wires meet at one point, on the back of the speedo or rev counter. Basically follow any black wire and find where it connects to the chassis or to other black wires and clean and tighten the connection. The main one in the boot has to carry the full starter motor load so needs to be really good, this bolt passes through the chassis into a bobbin moulded into the boot floor, the earth is then secured on this with a nut inside the boot, the nut inside the boot can be tight so the earth strap is tight to the bobbin, but the bolt can be loose in the chassis so not making a good contact, so check for this as it?s a fairly common fault, people who don?t know just tighten the nut inside the boot and forget that the connection has to be tight to the chassis too. Good luck , it?s just a matter of working your way around the connections methodically. You may have other problems with poor connections, but if you are sure all your earth connections are good it makes it easier to find any remaining problems.
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PostPost by: The Veg » Mon Jan 28, 2019 7:51 pm

And never assume that the earth that you think affects something actually does, or vice versa.

Case in point; a few years ago I had an Esprit that would do this weird thing where the fuel and temp guages would do this really slow, unison oscillation, slow enough that a few minutes between glances were necessary to notice it. Then one day I was under the back end, cleaning up after an oil and filter change (there is no way to change the oil filter on an Esprit without making a mess!), and noticed that one of the bolts on the engine-end of one of the engine mounts was loose, and it happened to pass through an earth-strap that was secured to the chassis at the other end. After tightening that connection, the oscillation was never seen again! I still don't know how the engine-end have relates to those two gauges and I probably never will, but I was still quite happy with the result!
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