Chassis ground????

[nomad]

How concerned should I be about grounding? Should I run extra ground wires or just eliminate the ground by the battery and run a ground cable clear up to the engine?

Kurt

[bitsobrits]

How concerned should I be about grounding?

I would say "very". Ensure all your grounds eventually go to the threaded holes in the chassis, not the 'through' holes as the factory did at the very rear of the chassis and you should be fine.

Below is how I've grounded my last few Elans in the rear: with a stud threaded into a diff mount hole and a stand off that brings the securing nut up into the trunk area for easier access.

Front grounding points would be the front turrets, the two vertical body bolts just behind the dash panel, and the unused parking brake cable guide (right side on LHD cars and left side on RHD) which is handy for an engine to chassis ground.

[nomad]

Thanks, Steve.

Some of the original points seem a little dodgy. I was going to run a bead of brass around the battery to frame hole to get a better less likely to corrode connection and forgot to.

Kurt

[Andy8421]

How concerned should I be about grounding? Should I run extra ground wires or just eliminate the ground by the battery and run a ground cable clear up to the engine?

Kurt

Resistance of a conductor is a combination of the resistivity of the material used, its cross sectional area and its length. Copper's resistivity is approx 5x lower than steel, but in the case of the Elan, the cross sectional area of the frame is going to be very much greater than a battery cable size copper conductor. You also have the advantage that the frame extends to most areas that you need a ground, and is 'free' - using a copper conductor would be worse than using the frame.

As Bistobrits points out, the problem is not the frame being used as a ground, but the ropey connections to and from the frame. The worst culprit is the battery earth cable in the boot floor which always seems to come loose. Bitsobrits solution looks very good, I plan to copy this for my next rebuild.

Most of the auxiliaries in the Elan come from cars expecting a steel body earth return, and the rats nest of ground cables in the Elan trying to replicate this can be a major source of electrical grief. Checking that the these grounds are intact and are ultimately solidly connected to the frame will solve many electrical issues.

[RichardS]

I earthed my battery to the rear suspension turret, as suggested by Brian Buckland. It works well, and is a nice dry location.

Described in this post viewtopic.php?f=38&t=18471&start=

Richard

[HCA]

How concerned should I be about grounding? Should I run extra ground wires or just eliminate the ground by the battery and run a ground cable clear up to the engine?

Kurt

I have done pretty well this - a cable from battery up to a block that I can feed various grounds into. By using thinwall cable in the wiring loom, there is plenty of room now to individually ground each device.

I agree to having grounds to threaded points and even better threaded studs welded to the chassis.

[nomad]

Andy 6421 makes a good point about conductivity of the frame versus a cable. The only really ugly point is that battery ground going to the frame at a point particularly prone to corrosion. Wish I had put brazing on that point. The idea of connecting at the turret is a good one but then I end up with more unsightly cable in the cabin.

Well, its a bit before I have to tackle grounds anyway so will cross that bridge...

Kurt

[jk952]

With my S2 battery behind the seat as is usual position, I used a socket head cap screw for the tunnel seat belt mount - ground the serrations on the side of the cap screw a bit to smooth and slightly tapered like a battery terminal then attached a standard battery terminal (actually via a cut off switch I can reach seated) & cable then the short distance to the battery ground terminal.
Also is nice and easy to isolate battery without opening the trunk or whatever to access the switch whenever parked.
Jack

[nomad]

Excellent, Jack, and another option!

Kurt

[Quart Meg Miles]

I don't have a problem with the chassis ground as it is well lubricated by my oil leaks. I recently measured 0.3V drop from isolator to engine on cold (summer) start but I'm losing 3.0V across the isolator!

It is a cheap isolator but what do most people lose across theirs?

It's resistance also gave me a problem with the fuel pump's intermittent current pulses causing my LED sidelamps to flicker badly (which I cured yesterday by wiring the pump straight from the battery with it's own isolating relay). Other people must have the same problem but I don't recall it being mentioned.

[HCA]

A 3V drop? wow. high. No wonder your fuel pump does not like it!

I can only think that you have a huge crud build up on the contact points. This build up could, I guess, be due to inferior metal quality but also due to isolating with a load of some sort still connected.

[rgh0]

I use a Hella isolating switch ( big red key) in my Elan in the cockpit plus a generic battery terminal isolator of the screw tight kind ( green knob). No measurable voltage drop across either while cranking

cheers
Rohan

[Quart Meg Miles]

Thanks for the rapid response to my off-topic!

I repeated my measurements and the starting drop was more like 1.5 V but with the isolator removed just 0.25 V and it sounded faster. I've already ordered a genuine Hella switch (500 A for 10 seconds) and it should bolt straight in.

This is the link between cable and chassis; it drops over the end of the chassis bolt (already nutted down) and is held on by another nut. It's been in since 2013 and never been abused but is rather touchy about where the handle is.

[jk952]

For interest this is what a popular isolator switch looks like inside. There is just a small spring (barely visible in the white plastic part) pressing the copper bar against the two flat surfaces (identical one not shown). With those bolts mounted in plastic, nor precision machined surfaces, it is not hard to imagine getting three relatively small contact points between the two terminals.

Jack

[Andy8421]

Copper isn't great for a low voltage high amperage switch like this. Copper will oxidise over time, and reliable copper contact switches are designed with either wiping contacts, high contact pressures or run at high voltage.

These isolator switches have none of the above. When I tried my Elan after 5 years in storage, the isolator switch did exactly that - it isolated the battery in both the on and off position. They really aren't a great design, if left unused for a long period of time will stop working.