14 replies to this topic

[Tumbleweed-Connection]

Hi forum,

 

Went to Halfords yesterday for a free battery check as it seemed as though I couldn't have the lights on for ten minutes after having stopped before the battery went flat. They told me the battery itself was ok (78% healthy), so it must be the alternator itself or a loose belt as there was a lack of voltage going back in.

 

I came home and checked the belt itself and there is definitely no play in that - used the basic 90 degree twist check. I understand that commonly the earthing points can get corroded, particularly the one in the engine bay, attached to the steady arm. Having checked the negative lead coming off the battery in the boot and finding it all fine, I thought I may as well replace the earth strap in the engine bay and even add a second strap as recommended to see if that cures the issue. Unfortunately, I don't have a multi-meter to check voltage of the alternator, so I'm sort of doing this by braille.

 

Question is, considering pretty much everyone says that the braided cables like the standard included one are rubbish, can I (and should I) actually replace this with a covered cable like this one:

 

http://www.halfords....ry-cable-22cm-9

 

I know this is designed for the negative terminal of the battery, so would the gauge of the wire be an issue here? Is there a reason why they use the braided cables for this rather than something a bit more substantial?

 

Thanks

 

Jacob

 

[nicklouse]

They should be e the same size so makes no difference.

I would also buy a multi meter.

[Tumbleweed-Connection]

Thanks for the quick reply.

 

Yeah, I probably should to be honest. My dad has a spare which he says just needs leads, so he'll bring it down to me when he next sees me. That's why I'm holding out really.

 

When you say it makes no difference - as in it makes no difference as to the longevity of the strip? I know pretty much jaff all about electrics but the basics, but I thought perhaps the fact that the covered cables are thicker may have an impact on the earthing properties (though I know it's technically not an "earth", but a negative)?

 

Looking to pop down to Halfords today and see if I can sort this. Already been once and bought a braided earthing strip that was much longer than it needed to be, so taking that back!

Edited by Tumbleweed-Connection, 12 April 2015 - 08:28 AM.

[KernowCooper]

Your going to Halfords, may as well go to Mcdonalds and ask for a check/advice, seeing the naff wiring I've sorted out from there. yes a Voltmeter is your next step

Edited by KernowCooper, 12 April 2015 - 04:17 PM.

[Rog46]

Current going in the battery (-ve) MUST be the same as that coming out (+ve) so absolutely fine electrically!

A thicker cable is always better, a covering will prevent (delay) corrosion in the cable itself and look smarter

[Cooperman]

I always use a length of battery cable for the engine earth and connect it to the clutch cover rather than the engine steady and from there to the inner wing.

[Tumbleweed-Connection]

I always use a length of battery cable for the engine earth and connect it to the clutch cover rather than the engine steady and from there to the inner wing.

I did connect a second earth (covered negative battery lead, as suggested) yesterday. Earthed through the existing point on the right hand side where my front fogs are also earthed. I did consider connecting to the clutch cover, but for some reason ultimately decided to connect to the front bolt on the steady bracket. Might change this as I'm a bit concerned whether the heat from the direct proximity to the engine might melt the covering. Not sure if those things are meant to take that sort of heat generally.

[Rog46]

Generally speaking I would expect the individual strands in a battery cable to be thicker (but less of them) this would mean that the cable will be less flexible and more prone to damage from flexing due to engine movement!

[fenghuang]

.... My dad has a spare [multimeter] which he says just needs leads ...

[A bit OT but...]
The last time I looked for replacement leads they were about the same cost as a cheap meter. (Not that that's a good reason to by poor quality tools or scrap a meter for the sake of a lead.)

[spiguy]

Like cooperman, I just added a 2nd earth strap from the engine steady on to the clutch servo cover. That's a decent and easily accessible location to earth onto. Remember for checking your fan belt tension, that you need to use the long run between the alternator and the bottom pulley to assess tension, not the short run from the alternator to the water pump as it is too short and with the belt properly tensioned will seem very tight indeed. If you assesed it there then there is a good chance it is too slack.

 

I have also found that you can have a slighlty loose fan belt on a mini without the tell tale screeching - I had a mini where the alternator was not charging, and it was due to the belt being slack, but it never screeched!

[Titchywitch256]

 

.... My dad has a spare [multimeter] which he says just needs leads ...

[A bit OT but...]
The last time I looked for replacement leads they were about the same cost as a cheap meter. (Not that that's a good reason to by poor quality tools or scrap a meter for the sake of a lead.)

 

 

I got mine from B&Q for a tenner

[fenghuang]

I got mine from B&Q for a tenner

i assume that was a meter, rather than leads.
You should be able to get one with a dwell function for about £29.

[Tumbleweed-Connection]

My dad works at a building college, so lets just say he has managed to "source" some leads for the spare meter he has. He seems to think it's quite a posh one - a Fluke something or other. You can't beat free anyway.

 

I'm fairly sure this hasn't solved the charging issue anyway, but I'll wait until I get hold of the meter and can test the outputs myself to be sure. Took the car for a fairly long spin and the indicator on the battery itself still suggested it needed charging. When the engine is running at idle, the volt meter is indicating around 13.75 volts (about half way between the 13 and the next marker), so as an approximation this would suggest everything was ok, though I know closer to 14 is really what we're after.

 

Not the most concrete conclusion, I know; I need the proper equipment. I could take it back to my local Halfords for another Free Battery Check on the sly I suppose...

[Tumbleweed-Connection]

...Remember for checking your fan belt tension, that you need to use the long run between the alternator and the bottom pulley to assess tension, not the short run from the alternator to the water pump as it is too short and with the belt properly tensioned will seem very tight indeed. If you assesed it there then there is a good chance it is too slack.

 

Definitely checked the deflection in the longer run down the front, rather than top that runs to the coolant pump, but always best to make sure of course!

[Tumbleweed-Connection]

Checked everything out this evening as I finally have a volt meter and despite what the chaps at Halfords told me, I can see anything alarming in terms of the numbers I get. It may be that adding the second Earth has potentially solved the issue. Here are my findings anyway (I know they're not perfect numbers and could be better, but they all seem in the right ball park):

 

Readings with engine off:

Battery = 11.96v (battery is not fully charged before testing, so this is likely expected)

 

Readings when engine on at idle:

Battery = 14.07v

Alternator = 14.2v

 

Readings at 3000 rpm:

Battery = 14.08v

Alternator = 14.2v (Assume the alternator output may be limited to 14.2?)

 

Load Test with front fogs, headlights and heater on full and engine idle:

Battery = 13.84v

Alternator = 14.2v

 

As I say, everything seems fine. The loss from the alternator to the battery is less than perfect, it seems, but not too bad. Would you chaps say that given these numbers I should now be confident that I have solved the problem?

 

Thanks.