Earth srap

[Hettiherald]

Hi all
I have just been chasing a charging problem with the stag, and have found the problem at long last. The earth srap that goes to th engine from the battery was not earthing properly, despite it looking ok. I had put an additional srap to the body, but the engine end had a high resistance. The result was about 1 volt drop, not enough to stop the car starting, but enough to cause problems with all the lights on.
If you have a charge problem, replace the strap even if it looks fine, before you chase down everything else!
Dave

[wilf]

Another reminder that so many electrical problems are actually mechanical, thanks!

[RobinLegin]

Hi all
I have just been chasing a charging problem with the stag, and have found the problem at long last. The earth srap that goes to th engine from the battery was not earthing properly, despite it looking ok. I had put an additional srap to the body, but the engine end had a high resistance. The result was about 1 volt drop, not enough to stop the car starting, but enough to cause problems with all the lights on.
If you have a charge problem, replace the strap even if it looks fine, before you chase down everything else!
Dave

Hi Dave
How could you tell this was the problem? I have just has an electronic cooling fane installed, and the battery seems to be forever need charging back up. The alternator is giving the right charge out, and my local expert thinks the earth leads OK. Drove the car yesterday a few miles (I know not ideal) but it took nearly 3 hours to charge the battery up again.
Nigel

[GDPR]

Easiest way is put a digital voltmeter between the battery negative, and the engine block. Start the engine and switch on all the lights, heater blower and HRW if the hardtop is still on. Bring the revs up to about 2000.

Check the voltmeter reading - anything over 0.2 - 0.3v reading on the voltmeter is not good - check the reading drops as you take the loads back off, and increase again as they are switched back on. This reading is the loss of voltage across the earth lead - you may have loads of current, but until the overall charging voltage is in the range 13.6 to 14.4v the battery either won't charge or boil dry, so any significant loss across this lead makes a big difference.

You can do a quick double check by placing a good heavy gauge jump lead between the battery and block to see if the reading is reduced - if it is the earth lead needs replacement or supplement.

You can of course get a similar issue on the charging lead between the alternator and battery - you can use a similar method to check it but much more care is needed to flash something to earth and do something you'll regret.

Russ

[Stagsongas]

I've just finished the first stage of a long planned Battery replacement/upgrade/relocation.

Prior to that my engine would often stall at any RPM and around mid-temp. Thankfully it would eventually restart and all would be well until the next cold start. I suspected the Ignition system and followed all advice and ideas of my own to no avail.

Since the car now has upgraded + and - connections at the Battery end, it hasn't missed a beat at any temp. A happy accicdent and a bit of luck - the problem simply must have been caused by a connection somewhere along the line, and this serves to show that doing the basics on the + and - leads and connectors is crucial, even if only for elimination.

Regards

Steve

[RobinLegin]

Have just taken the mean green machine for a 30 mile run mixing some 15 miles of urban driving around Bournemouth and Poole Sandbanks, then out on the A31 dual carriageway for a 70 mph burn up. I noticed the fan was cutting in when the needle was not even halfway across the gauge.I stopped a couple of times and adjusted the setting on the thermostat. When we got home I put the battery on charge - and it went green within 5 to 10 minutes. So a big improvement.
However the charge appears to be at 14 volts on the dashboard. Is this about right? we were driving around for about 50 minutes.
Thanks
Nigel

[Hettiherald]

Hi nigel. Russ has given a good answer as he always does. But , if you are not very technically minded, i would always replace the original earth strap. It could be around 40 odd years old and have had a fairly hard life. The cost isnt excessive, and it takes out one of those niggles that always takes an age to find.
Good luck
Dave

[GDPR]

Please Nigel - only take the dashboard voltmeter as a bit of decoration only - I have a digital voltmeter permanently set up, via an accessory feed powered relay to the battery terminal using a wire easily capable of moving 60 amp (I power the radio, and several USB/cigar lighter sockets from it) so it has virtually no volt drop - my smiths voltmeter reads nearly 15v when my digital reads 14.2v

My brother who repaired and flew DC4s and the like would have described it as "wind and p1ss instruments" - better than nothing, but only just. They are hot wire gauges, so as a voltmeter not to be relied on. If you have a digital multimeter, compare the reading with the dash unit and just make a mental note - then if it reads grossly different you know to investigate, otherwise ignore it

[RobinLegin]

Thanks Russ

Will invest in a digital voltmeter and test everything next weekend. Off to Sweden tomorrow - land of Volvos. However we are off to France on the 25th so will be committed whatever as the Grey Lady's engine is in bits and we are meant to be taking part in the rally with a classic car.
Nigel

Please Nigel - only take the dashboard voltmeter as a bit of decoration only - I have a digital voltmeter permanently set up, via an accessory feed powered relay to the battery terminal using a wire easily capable of moving 60 amp (I power the radio, and several USB/cigar lighter sockets from it) so it has virtually no volt drop - my smiths voltmeter reads nearly 15v when my digital reads 14.2v

My brother who repaired and flew DC4s and the like would have described it as "wind and p1ss instruments" - better than nothing, but only just. They are hot wire gauges, so as a voltmeter not to be relied on. If you have a digital multimeter, compare the reading with the dash unit and just make a mental note - then if it reads grossly different you know to investigate, otherwise ignore it

[RobinLegin]

I was offered two options at Halfords. One was the open braded steel wire, the other was I think copper wire covered in black insulation. Neither are the right length but since the earth is bolted onto the bodywork about half the length before going on to be bolted to the engine, I think the mission can be accomplished using 2 sections bolting both where fixed to the bodywork. Each section is 0.6m.
The question is which is best? The traded steel wire in 2 sections, or the insulated copper in 2 sections.
I have bought the traded wire, but since I am away till the weekend I have time to change this.
Nigel

[GDPR]

Open braided would be my choice - easy to check for deterioration, and due to no insulation (completely unnecessary on an earth, more flexible without it due to the plastic stiffening with time/temperature) more durable.

If you get the chance, flow the end terminal crimps with solder and avoid future corrosion high resistance in the crimp joints - dip the end in plumbers flux, heat the terminal with a small blow lamp/cooks torch and feed the solder in - definitely worth the extra effort

[marshman]

Open braided would be my choice - easy to check for deterioration, and due to no insulation (completely unnecessary on an earth, more flexible without it due to the plastic stiffening with time/temperature) more durable.

If you get the chance, flow the end terminal crimps with solder and avoid future corrosion high resistance in the crimp joints - dip the end in plumbers flux, heat the terminal with a small blow lamp/cooks torch and feed the solder in - definitely worth the extra effort

Agree it's not a bad idea to flow some solder into the crimped ends to improve long term reliability. Also agree plumbers flux is good stuff BUT make sure you clean ALL the flux off when you have finished soldering, this is an important step that many people leave out. The flux is good because it is corrosive! if you don't remove it it will continue to do its thing, and attack the thin copper wire making up the braid with obvious long term consequences.

Roger