Juice problem?

[Sundowner]

In all the time I've had it, my Sprint has had a small problem that I've been putting up with, but because of an upcoming 1,600kms trip, I'd like to sort out now.
*) The lights are dull. This includes indicators, head lights, both high & low, parkers, interior, dash........ALL of them.
*) The temp gauge and fuel gauge both read low, by about 1/3rd.
This is despite replacing the Voltage Stabilizer and the fuel tank sender unit a couple of years ago. At that time, I also cleaned up as many earths/grounding points as I could find.....which made no difference at all.
I'd appreciate any suggestions as to overcoming this, apart from the obvious...."don't drive at night"
Cheers,
Rob

[Mad Mart]

It will definitely be an Earthing problem. With everything dull then it's likely the main Earth to the body is at fault, so check the smaller cable from the battery -ve to the inner wing. You can check for a good connection using a multimeter. Check across the battery terminals to see what voltage you have there. Then, with the positive lead of the MM on the +ve battery terminal, test different places around the engine bay (not the block itself, that has a separate Earth) and see what voltages you get. You should get similar readings to the battery.

[Mahesh]

Also worth checking with a meter in ohms across the positive of the lights to earth (negative).

There is a chance one of the positives could be grounding, (complete or slightly) not enough to
blow a fuse, but enough to drag the circuit down.

Happened on a Honda Civic where the garage changed the battery and a lead got trapped,
two days later, endless ECU errors and a week to track down the fault, because it didn't happen
immediately.

In your case you could have a lead which is either chaffed or melting and then shorting.

[Sundowner]

Thanks Gents,
I'll get onto it today.
Cheers,
Rob

[tinweevil]

Thanks Gents,
I'll get onto it today.
Cheers,
Rob

Can I just add that in this investigation make no assumptions at all to ridiculous extremes. Don't assume that voltage at the battery post is the same as that in the battery clamp. Don't assume that the voltage in the clamp is the same as the voltage in the copper inside the crimp. Don't assume that 2 cables under the same bolt are at the same voltage and nor the bodywork under the bolt. Take measurements across joints and referenced back to the +ve and -ve battery terminals. Anywhere and everywhere you can get a multimeter probe in check for a voltage drop.

When I rewired my headlights I was losing up to 1.69V +ve and 0.48 -ve measuring from the light terminals to the battery posts. It was going in little bits right through the system though the biggest single loss was in the main switch. Rewiring increased the voltage at the bulbs by about 1.5V so roughly 11% more power into the bulbs rather than wasted as heat in the loom/connectors/switches.

[Mad Mart]

Yes, what Julian said ^^^.

Measure across the battery terminals. Measure from the +ve terminal to the -ve terminal clamp, then to the other end of the earth cable. Everywhere there is a connection it could be a bad connection.

[Sundowner]

I've just had a quick look at it (before breakfast, and on a Sunday too) and found that there is no drop from the positive terminal to all points in the engine compartment.
Will look further, later.
Thanks heaps for the tips.
When it comes to auto electrics, I make a good house painter.
Cheers,
Rob

[tony g]

One thing I hate in these looms is the connector just above the gearbox visible from engine bay.
This connector has 2 red/white thick leads (on the loom side) and a "loop" on the gearbox side.
This loop takes the place of the starter feed when an auto is fitted to go to the inhibitor switch on the auto.
Basically the feed goes down to the multiplug, around the loop and back into the multiplug engine side. A bad connection here can give strange voltage drops too.
On mine I cut and joined the wires on the engine side so it doesnt have to go through 4 bullet connectors.


Tony

[Mad Mart]

What voltage are you seeing?

[Sundowner]

Mart,
I'm getting 11.9V (on my Cheap n Chinese multi meter). And that's everywhere from the Positive battery terminal to just about everywhere else under the bonnet.

Tony,
That connector has obviously been tampered with at some stage as there is only the red/white loop still in place, with other coloured wires coming and going on the other side. But I cant find a drop there.

I'll extend my search to beneath the dashboard next as I know that a previous owner installed a CD player that I suspect isn't done right. The problem could be there....who knows?
Thanks for answering Gents, and should you know of any other historically proven problem spots please let me know........What about the light switch? Its new at sometime in the cars past as there is a used one in the spares box.

Cheers,
Rob

[Mad Mart]

11.9V is too low, it should be 12.6V. Get the battery charged first then see how it goes.

[Sundowner]

11.9V is too low, it should be 12.6V. Get the battery charged first then see how it goes.

Yes, I know that reading is too low, but its consistent.
I'm almost certain that its the multi meter that's giving an incorrect reading, as the car is kept on a C-Tek trickle charger, constantly.....and the battery is relatively new.
Rob

[Toledo Man]

Get a digital multimeter. They will give an accurate reading and don't cost the Earth.

[Mad Mart]

OK Rob, although you have a cheap Chinese MM I doubt it's that inaccurate. Next test the alternator output. While the engine is running, check the voltage across the battery terminals. It should be 13.8V-14.2V or there about. Now put your lights and anything else you would have on whilst driving in the dark (engine still running). Are you still getting about 14V across the battery? If it drops significantly then your alternator is at fault.

[MIG Wielder]

Just as an idea it would be good to measure these voltages using the battery 0V or negative post as a reference.
I would start by running up the engine, setting it to give a fast idle, then start with the lighting circuit. Turn on main beam.
Now measure and note the voltage from the battery negative post to the alternator body metalwork. This should be quite a low voltage.
Now measure from battery negative to the positive post.
Then from negative post to the positive cable clamp.
Then from the negative post to the alternator thick brown wire connection at the alternator.
Now measure from the battery negative pole to the black wire where it connects to the back of the main beam ( outer ) headlight.
And finally from the battery negative pole to the blue/ white wire at the back of the headlight.
If you can give us these numbers then we can make an informed guess as to where the lighting circuit problem is.