Donate to Remove ads

Got a credit card? use our Credit Card & Finance Calculators

Thanks to johnstevens77,Bhoddhisatva,scotia,Anonymous,Cornytiv34, for Donating to support the site

fault diagnosis

Passion, instruction, buying, care, maintenance and more, any form of vehicle discussion is welcome here
James
Lemon Slice
Posts: 295
Joined: November 4th, 2016, 3:12 pm
Has thanked: 69 times
Been thanked: 111 times

fault diagnosis

#220878

Postby James » May 11th, 2019, 3:22 pm

Hello
Up-front confession: I'm not a car person. That should be evident from the fact I drive a 2002 Rover 25.
The problem I have is that the battery is running flat, and the battery/alternator light on the dash has gone from flashing intermittently to staying on full-time. I've taken to charging the battery via a charger ahead of going anywhere.
On the last short trip I took, the car started, got me six miles, then restarted. But on the ride back, I noticed the electrics seemed to go dead intermittently. The car was still running but the radio would switch off, and the speedo and rev counter dipped to zero briefly, before it all came back on.
I'm guessing this means I need a new alternator, which at £200 to have installed is £200 more than I paid for the car.
But I thought I'd check the collective wisdom here first in case I might have missed something obvious.
J

Slarti
Lemon Quarter
Posts: 2941
Joined: November 4th, 2016, 3:46 pm
Has thanked: 640 times
Been thanked: 496 times

Re: fault diagnosis

#220914

Postby Slarti » May 11th, 2019, 5:06 pm

Have you looked at the fan belt to make sure that it is turning the alternator?

Also, about 4 cars back, so at least 25 years ago, my newly purchased 2nd hand car died half way to Ipswich, from Chelmsford.

Obviously an electrical fault, so I called the AA and when the guy arrived told him that all of the electrics had died. First he looked at the fan belt because it drives the alternator, and then poked around and noticed that the earth strap was not tightly connected. Tightened it up, jump started the car and it was fine from then on. So check your earth strap.

HTH
Slarti

sg31
Lemon Quarter
Posts: 1543
Joined: November 4th, 2016, 11:35 am
Has thanked: 925 times
Been thanked: 708 times

Re: fault diagnosis

#221043

Postby sg31 » May 12th, 2019, 11:37 am

It could also be a battery fault. Find your nearest battery supplier and take the car in, they should be able to test the battery straight away.

It's a quick and easy way of checking one possible problem.

If you have a voltmeter or if you have a friend who has one you should be able to test the alternator. Connect the leads appropriately to the battery terminals and start the car. If the alternator is working you should get a reading of 14.2 to 14.7. (I think these are the right figures, it's a while since I last needed to do this so may have mis-remembered). If the reading is within the band it's likely to be ok.

If the battery and alternator are ok you need to find an auto electricial. They will usually do a cheap diagnostic test to find the problem, then you can decide to get it fixed or scrap it.

dionaeamuscipula
Lemon Quarter
Posts: 1095
Joined: November 4th, 2016, 1:25 pm
Has thanked: 101 times
Been thanked: 374 times

Re: fault diagnosis

#221284

Postby dionaeamuscipula » May 13th, 2019, 12:54 pm

James wrote:Hello
Up-front confession: I'm not a car person. That should be evident from the fact I drive a 2002 Rover 25.
The problem I have is that the battery is running flat, and the battery/alternator light on the dash has gone from flashing intermittently to staying on full-time. I've taken to charging the battery via a charger ahead of going anywhere.
On the last short trip I took, the car started, got me six miles, then restarted. But on the ride back, I noticed the electrics seemed to go dead intermittently. The car was still running but the radio would switch off, and the speedo and rev counter dipped to zero briefly, before it all came back on.
I'm guessing this means I need a new alternator, which at £200 to have installed is £200 more than I paid for the car.
But I thought I'd check the collective wisdom here first in case I might have missed something obvious.
J

I had a similar problem with a 90s era Honda which was not an altogether different car. The battery would just drain overnight. The alternator was fine, auto electrician unhelpful. I disconnected the battery overnight and carried a spare with me in the boot.

Eventually I solved the problem by selling the car.

DM

sg31
Lemon Quarter
Posts: 1543
Joined: November 4th, 2016, 11:35 am
Has thanked: 925 times
Been thanked: 708 times

Re: fault diagnosis

#221294

Postby sg31 » May 13th, 2019, 1:33 pm

dionaeamuscipula wrote:
James wrote:Hello
Up-front confession: I'm not a car person. That should be evident from the fact I drive a 2002 Rover 25.
The problem I have is that the battery is running flat, and the battery/alternator light on the dash has gone from flashing intermittently to staying on full-time. I've taken to charging the battery via a charger ahead of going anywhere.
On the last short trip I took, the car started, got me six miles, then restarted. But on the ride back, I noticed the electrics seemed to go dead intermittently. The car was still running but the radio would switch off, and the speedo and rev counter dipped to zero briefly, before it all came back on.
I'm guessing this means I need a new alternator, which at £200 to have installed is £200 more than I paid for the car.
But I thought I'd check the collective wisdom here first in case I might have missed something obvious.
J

I had a similar problem with a 90s era Honda which was not an altogether different car. The battery would just drain overnight. The alternator was fine, auto electrician unhelpful. I disconnected the battery overnight and carried a spare with me in the boot.

Eventually I solved the problem by selling the car.

DM


Been there with a Honda Accord. There was a drain on the battery from some part of the electrical system. An auto electrician tracked it to one part of the system which included all the expensive bits. Effectively one 'expensive bit' was causing the drain but he couldn't tell which it was without disconnecting them individually until the drain stopped. That would potentially have involved stripping out most of the car to access the appropriate items. It sounded like it could get very expensive.

The auto electrician fitted a gismo to the battery that disconnected the battery if the level of charge dropped to a level which would still be enough to start the car. All that was needed was to reset the gizmo by pressing a button, start the car and away you go. The only trouble was it caused problems with the alarm system. In the end I removed it and carried a starter pack that could always get me started.

Like you the problem was eventually solved when I sold the car.

TheMotorcycleBoy
Lemon Quarter
Posts: 3245
Joined: March 7th, 2018, 8:14 pm
Has thanked: 2222 times
Been thanked: 587 times

Re: fault diagnosis

#221352

Postby TheMotorcycleBoy » May 13th, 2019, 5:26 pm

James wrote:Hello
Up-front confession: I'm not a car person. That should be evident from the fact I drive a 2002 Rover 25.
The problem I have is that the battery is running flat, and the battery/alternator light on the dash has gone from flashing intermittently to staying on full-time. I've taken to charging the battery via a charger ahead of going anywhere.
On the last short trip I took, the car started, got me six miles, then restarted. But on the ride back, I noticed the electrics seemed to go dead intermittently. The car was still running but the radio would switch off, and the speedo and rev counter dipped to zero briefly, before it all came back on.
I'm guessing this means I need a new alternator, which at £200 to have installed is £200 more than I paid for the car.
But I thought I'd check the collective wisdom here first in case I might have missed something obvious.
J

If a new battery doesn't cure it, and you can't hear the alt. belt squealing most of the time (i.e. belt is gripping and turning the pulley), it's probably the alternator.

But the way you describe it could also that a terminal/connection is a tad loose.

My money is on the alt. if not fixed by a good battery and having a quiet belt.

Matt

jfgw
Lemon Quarter
Posts: 2540
Joined: November 4th, 2016, 3:36 pm
Has thanked: 1097 times
Been thanked: 1146 times

Re: fault diagnosis

#221411

Postby jfgw » May 13th, 2019, 9:11 pm

Reading the OP again,
James wrote:the battery/alternator light on the dash has gone from flashing intermittently to staying on full-time.

and
James wrote:I noticed the electrics seemed to go dead intermittently. The car was still running but the radio would switch off, and the speedo and rev counter dipped to zero briefly, before it all came back on.

IANAE but both of those suggest a bad connection rather than the battery. I cannot currently think of a fault that would cause both symptoms. Does the car start normally (full power to the starter motor)?

I think that the warning light would be off if the battery was faulty. The light suggests that the battery is not being charged by the alternator.

The circuits in a car are only (nominal) 12V but can be several amps so the connections need to be clean and tight. While the fault could be within the alternator itself, my money is on a bad connection elsewhere.

Julian F. G. W.

bungeejumper
Lemon Half
Posts: 8064
Joined: November 8th, 2016, 2:30 pm
Has thanked: 2846 times
Been thanked: 3939 times

Re: fault diagnosis

#221467

Postby bungeejumper » May 14th, 2019, 8:24 am

Long shot. When my old dad's 200 series Rover developed a permanent power drain, we finally tracked it down to a faulty switch in the boot that was keeping the boot light permanently on. Neither he nor anybody else had noticed it.

Second long shot. A wet carpet in the passenger footwell is causing an earth leak from the alarm/immobiliser. (Which is probably under the seat.)

Third and slightly less long shot. One of the wires that connect across the door and boot hinges of your car has got old and frayed. These are the wires that make the windows wind and the doors lock, and so forth. Any electric windows not working?

Most likely cause: a battery that's giving due notice, or a slack earth connection somewhere. But if you suspect a dying alternator, ask an auto electrician for a second opinion, because sometimes it's just a single chip that's gone and can be replaced.

BJ

DrFfybes
Lemon Quarter
Posts: 3732
Joined: November 6th, 2016, 10:25 pm
Has thanked: 1171 times
Been thanked: 1964 times

Re: fault diagnosis

#221505

Postby DrFfybes » May 14th, 2019, 10:25 am

James wrote:Hello
Up-front confession: I'm not a car person. That should be evident from the fact I drive a 2002 Rover 25.
The problem I have is that the battery is running flat, and the battery/alternator light on the dash has gone from flashing intermittently to staying on full-time. I've taken to charging the battery via a charger ahead of going anywhere.
On the last short trip I took, the car started, got me six miles, then restarted. But on the ride back, I noticed the electrics seemed to go dead intermittently. The car was still running but the radio would switch off, and the speedo and rev counter dipped to zero briefly, before it all came back on.
I'm guessing this means I need a new alternator, which at £200 to have installed is £200 more than I paid for the car.
But I thought I'd check the collective wisdom here first in case I might have missed something obvious.
J


I presume the warning light is related to low volts as this is easier to measure than charging current (this is just a guess), With the engine on it should be 12.8V or more and thick end of 14V as the revs rise. If an alternator is failing then often the light comes on at tickover or low revs first, so it sounds like a failing alternator.

If the failure on the return trip happened at low revs, then it could be the alternator not charging, which could also damage the battery.

A first quick check is to wiggle the battery terminals and check the end of the neutral wire where it bolts to the car to make sure they are clean and tight. Also have a look at the connector (and wires) to the alternator.

A fully charged car battery should be good for at least 30 min with a couple of starts, even with no charging going on. When the alternator failed on my Sierra I charged it each night and ran it 'Total Loss' (ie solely off the battery charge) for a couple weeks for the 10 mile round trip to work whilst looking for a used alternator before realising a new one was £70. Race bikes/cars also used to run this way to save weight and power drain.

Halfords, Kwik Fit, ATS, etc will all test your battery and alternator and tell you the condition (charge the battery fully before setting off). I found my local ATS to be quite keen to order me a replacement battery, whereas Kwik Fit (and later the main dealer at the service) both said it was 'a bit low but OK'. Other areas might have different standards.

Paul


Return to “Cars, Driving, Motorbikes or any Transport”

Who is online

Users browsing this forum: No registered users and 10 guests