Electrical problem - any thoughts?

[Scribe]

A while back I replaced both Battery terminals.  In July I went away for a few days and the car behaved faultlessly, including a high-speed journey home of about 100 miles on the motorway.  Four days later, parked on the driveway, everything was dead - not a light or a spark anywhere.  I disconnected the Battery (terminals were still tightly done up) and recharged it.  The car then started fine and went for its MOT.  My mechanic said he would replace the Battery (still under warranty) if necessary but that it was charging as it should, with no drain.

The next time I used the car, I got about a mile from home and it died on me - again, not a light or a spark.  I wiggled the negative Battery lead and the power came back on and I got home okay.  Battery power seemed normal - the car started as it should - but since then it's gone flat in a few weeks of non-use.  The car is going in to the garage on Friday to be investigated, but I thought I'd ask if anyone had any thoughts.  Could it be a loose connection in the Battery leads?  And would this cause a slow drain?  Or could it be something else? 

[Moleman]

31 minutes ago, Scribe said:

A while back I replaced both battery terminals. 

This would seem like a good place to start, especially if everything was working okay before you did this.

[Supafly]

When you have the problem do you check the voltage of the Battery?

I agree with Maurice above that your work on the terminals should be the first thing to be checked.  However, I've been caught out in the past by coincidence.

As you have charged the Battery it would be good to eliminate a parasitic drain.  I've recently found a quick easy way to check, is by measuring the voltage across fuses.

 

Parasitic Draw Diagnosis: Tips for Best Approach | Auto Service Professional

There are voltage drop charts available online. 

 

In the past I've used the multimeter in series with the negative lead but this has LED to blown internal fuses and disrupts power to the car.  This method I've found to be a lot quicker and easier.

 

[Herbie]

7 hours ago, Scribe said:

A while back I replaced both battery terminals. 

The first question has to be why did you do this? I've never needed to replace Battery terminals on any car I've ever owned in more than 47 years of driving.

Are the terminal connections tight and clean?

Have you checked (preferably undone, cleaned and tightened) the 'other ends' of the Battery cables, ie, from positive Battery terminal to starter solenoid then from solenoid to starter motor? And also the earth straps from the negative Battery terminal to the body and engine?

Finally, I'm a firm believer in using the proper trade, ie, mechanic for general mechanical work and auto electrician for electrical work, so if it were me I'd be taking it to an auto electrician to be sorted if I couldn't do it myself.

Same info as video above but just a bit more in-depth and also showing voltage drop charts:

 

 

[Scribe]

When I disconnect the Battery and put it on charge, the meter on the charger immediately reads about 90%, which makes me think this is a connection problem somewhere, not the Battery draining.  And I can't use the car until it's sorted, because when it cuts out, everything goes dead.

Herbie: my mechanic replaced one of the Battery terminals because it would no longer tighten enough to grip.  I later replaced the other one, which seemed to be going the same way.  This was before the car was checked over during the last MOT.  I'm assuming the problem is at what you call 'the other end', which I wouldn't attempt to investigate myself.

Thanks for your suggestions.

[Tinonline]

Battery terminals don’t usually misbehave much as said but I suppose like every car something unexpected can come up.

What is the Battery make and spec?

Alternator failure is a more likely issue but if the Battery is still in good charge you have a system fault.

Diagnosis is best done when the car is not operating correctly. When the car fails what exactly fails and what works and doesn’t work? Everything off - every lamp and light, dash? 
The more you can describe, increases chance of someone else recognising the problem. 👍🫣
 

 

[Malc1]

I'm fearing there's going to be on-going potential unknowing electrical gremlins as our cars get older 

I experienced lots of weird gremlins which i reported here on last year or so ............. we've got quite ancient cars and must now expect these little challenges I'm afraid 

Others don't suffer as we do .....  their cars just don't exist at the age of ours ......  theirs' have long gone to the scrappy 😂

Malc

[Tinonline]

Hang on…you wiggled the negative lead and it came on? Sorry you did say not a spark ie spark of life.

Earth lead and or clean effective earth.

there are a number of Earth points but none would cause complete power loss. Except a main power lead.

Isn't there a restart sequence following a Battery disconnect? If you don’t need to do that then it’s a main connection issue…

[MLW]

I have to say, on 'tricky electrical issues' an real auto electrician is the best course.

A good auto electrician with all his testing gear will have it found and fixed in one hour tops. They just do auto electrics. That is their stock in trade. A mobile guy is OK, but find a real auto electrician shop. Once had a tricky headlight. In 25 minutes it was fixed. VW would have replaced the whole headlight unit by a 'fitter' at £150+++.

Merely replacing parts is very expensive. A good electrician will find it in 30 minutes.

[Malc1]

53 minutes ago, MLW said:

A good electrician will find it in 30 minutes.

Unfortunately when I had my electrical gremlins there wasn't a single local auto electrician that was able nor willing to even try to get to grips with whatever might have been the problem with my old lady

On balance I quite agree with you BUT specifically even the specialists can get spooked with aged electrics 

and that's simply what we're faced with in our old ladies 

 

Malc

[Scribe]

When the power goes, it goes completely - as if the Battery has been disconnected.  So if you're driving, there's a single warning ping and suddenly you're coasting, with no lights, indicators, wipers, electric windows etc.  And presumably no power to the brakes or steering.  This has happened twice, but I've managed to get a reconnection by fiddling with the terminal or the negative lead.  When this happens, the ignition lights come on again, so you know you're back in business.

I'm assuming it's a failing connection somewhere, because the Battery turns out to be not flat.  Happy to go to a specialist auto electrician but, as Malc says, it's not easy to find one nearby.  And I don't want to drive any further than I have to with the car in this condition - it's nerve-wracking, because the power could go at any time.  I certainly wouldn't take the car anywhere after dark or in rush hour.  A mobile technician seems logical, but how do you know if they're any good?

[PCM]

I tend to look at multiple reviews...

And check the reviewers, where possible are genuine, and not leaving 'worldwide' reviews.

( e.g., https://www.autoelectricdiagnostics.co.uk/ )

[cruisermark]

18 minutes ago, Scribe said:

When the power goes, it goes completely - as if the battery has been disconnected.  So if you're driving, there's a single warning ping and suddenly you're coasting, with no lights, indicators, wipers, electric windows etc.  And presumably no power to the brakes or steering.  This has happened twice, but I've managed to get a reconnection by fiddling with the terminal or the negative lead.  When this happens, the ignition lights come on again, so you know you're back in business.

I'm assuming it's a failing connection somewhere, because the battery turns out to be not flat.  Happy to go to a specialist auto electrician but, as Malc says, it's not easy to find one nearby.  And I don't want to drive any further than I have to with the car in this condition - it's nerve-wracking, because the power could go at any time.  I certainly wouldn't take the car anywhere after dark or in rush hour.  A mobile technician seems logical, but how do you know if they're any good?

Does the engine cutout aswell?

[Scribe]

Yes, the engine cuts out too, so you grind to a halt in gear.  Last time this happened I checked the Battery terminals (still done up tightly) and, for want of anything else to try, wiggled the negative lead.  I heard something happening under the bonnet, checked inside and the ignition lights were back on.  Power to everything, and the car started up as normal.  I took it straight home, where it's been since.  Too scary to use till it's fixed.  I don't want anyone to say they can't find anything wrong with it - I want them to say what the problem is and how they've fixed it, because I can't use a car I don't trust.  Hope that makes sense...  Meanwhile I can find just one mobile auto electrician who'll come and have a look.

 

[Tinonline]

1 hour ago, Scribe said:

Yes, the engine cuts out too, so you grind to a halt in gear.  Last time this happened I checked the battery terminals (still done up tightly) and, for want of anything else to try, wiggled the negative lead.  I heard something happening under the bonnet, checked inside and the ignition lights were back on.  Power to everything, and the car started up as normal.  I took it straight home, where it's been since.  Too scary to use till it's fixed.  I don't want anyone to say they can't find anything wrong with it - I want them to say what the problem is and how they've fixed it, because I can't use a car I don't trust.  Hope that makes sense...  Meanwhile I can find just one mobile auto electrician who'll come and have a look.

 

You do right not driving the car.

So following that you replaced Battery cables…and fault remains? You replaced Battery after the fault too? Sorry I’m not clear on events sequence…

 

 

[Scribe]

The Battery is about 18 months old and, according to my mechanic, is charging as it should when the engine's running.  When he fitted it he replaced the negative terminal because it was old and looked insecure.  I've since replaced the positive one.  When the Battery is reconnected after a recharge, everything comes on as it should and the car runs normally.

I'm hoping the fault is traceable somewhere between the terminals and whatever the cables connect to at the other end.  Don't laugh, but there was a smell of dead rat in the garage a few weeks ago, so I'm even wondering whether one has been nibbling under the bonnet - it's not unheard of. 

Three times now the car has gone lifeless on me, twice while I was driving it.  On those occasions I was able to stop safely, not far from home, but it might have happened while I was cruising on the M40 late at night back in July.  I'd have had no lights, no hazards, nothing...  Scary thought.

[Scribe]

So no, I haven't replaced the Battery cables, but obviously will do if they're the problem.

[Tinonline]

Oh boy…a rat…my nickname was pied piper of Selborne court…we had a massive rat infestation and I volunteered to tackle it…wiped them out but it took a lot of cunning and months…damaged 2 cars.

Seriously also, is there a smell under the bonnet? They will get there and chew on the wiring and cables. 
Sounds like a main cable in the supply is at fault.

If problems started since mechanic touched it that is suspect and I’d be expecting him to check his work or a rat has caused specific damage and may continue so keep opening the bonnet and make noise. Best to set a rat trap too with dark chocolate as bait if it’s a snap trap.

I think this is a very annoying issue rather than a show stopper. As long as no further damage ensues. 🫣🤞

[Herbie]

You have to be logical and methodical when dealing with electrics and logic says that if you wiggle the negative lead and it makes a difference, then there's probably something wrong with that.

Follow it from the Battery to wherever it's terminated and make sure the connection is clean and tight. Also check other earth straps from body to engine and some cars also have body or engine to gearbox straps. Alternatively, try using a jump lead or other piece of cable and try not to disturb anything else but just touch the negative Battery post with one end and any bare unpainted metal/nut/bolt/screw with the other end. If that works and you can repeat it each and every time, then you've proved that the earthing is faulty.

If you don't want to tackle it yourself, you don't say which part of Sussex you're in but here's a couple of places with good reviews:

https://www.autoelectrical-crawley.co.uk/car-electrician-sussex.html

https://www.stevesautolancing.co.uk/

https://www.autoelectricdiagnostics.co.uk/services

https://www.tmeautoelectrical.co.uk/

[royoftherovers]

12 minutes ago, Herbie said:

You have to be logical and methodical when dealing with electrics and logic says that if you wiggle the negative lead and it makes a difference, then there's probably something wrong with that.

Follow it from the battery to wherever it's terminated and make sure the connection is clean and tight. Also check other earth straps from body to engine and some cars also have body or engine to gearbox straps. Alternatively, try using a jump lead or other piece of cable and try not to disturb anything else but just touch the negative battery post with one end and any bare unpainted metal/nut/bolt/screw with the other end. If that works and you can repeat it each and every time, then you've proved that the earthing is faulty.

If you don't want to tackle it yourself, you don't say which part of Sussex you're in but here's a couple of places with good reviews:

https://www.autoelectrical-crawley.co.uk/car-electrician-sussex.html

https://www.stevesautolancing.co.uk/

https://www.autoelectricdiagnostics.co.uk/services

https://www.tmeautoelectrical.co.uk/

I must confess to being somewhat surprised Herbie, that NASA has not yet invited you to sort out its problems with Artemis 1.🤣

[ColinBarber]

1 hour ago, royoftherovers said:

I must confess to being somewhat surprised Herbie, that NASA has not yet invited you to sort out its problems with Artemis 1.🤣

I'm not sure Herbie wants to be associated with that overpriced bag of bolts. 🤣

[Malc1]

1 hour ago, royoftherovers said:

not yet invited you to sort out its problems

to ensure it's not a rodent maybe go borrow someone's cat for a day to sniff it out - chase it away or eat it 

Malc

[Tinonline]

2 hours ago, Malc1 said:

to ensure it's not a rodent maybe go borrow someone's cat for a day to sniff it out - chase it away or eat it 

Malc

That’s hilarious…like you can borrow a cat.😂

A ratter dog would do it…

Buy a plastic rat poison box…use only dark chocolate for a few times: then introduce a large trap that fits exactly to box. Get you’re rat. You can buy as a set.

Take out trap and replace with poison. Include chocolate. Leave. Be patient…there’s more than one rat…go looking for the nests. 

[Malc1]

cats come free and will soon be your friend if they see you're giving them summat to do to get them playful

Not keen on the poison route tbh

Malc

[Herbie]

One other thing has just plopped into my head re the negative lead. Battery clamps can be overtightened and if that happens the Battery post itself can break its connection with the negative plate in the Battery case, so make sure it's not the post itself causing the intermittent fault.