Alternator? Battery?


Mornin` chaps

Ok. So I`ve changed the brushes in the alternator. On tick over the multimeter that I connected across the battert reads around 11.76 but the voltage appears to steadily go down. When I rev the engine the meter reading goes steadily up and is now reading ( I have it running as I write) 13.02 and still rising. Am I correct in assuming that the alternator is producing a charge. I`m just wondering if the battery needs to be put on charge? Could the charge light and the fuel drain light come on if the battery was low? What do you think clever people?


If you mean the fuel gauge light is 'on' this indicates an empty fuel tank. If the 'battery charge' light is on then the battery is not being charged. Each light works independant. If they are both 'on' then there is a fault with each system. Before going any further ...
1. battery charge .......... I suggest you get the battery checked. Most diy shops provide a free test.The alternator could be OK but the battery plates might be useless. The 11.76v across the terminals is low and suggests a failed battery which wont hold a charge.
2. the fuel gauge ......... assuming the tank has several gallons of fuel there is an electrical problem. The fuel float/gauge inside the tank could be stuck in the 'empty' position. [did you run the tank dry recently?] Try violently shaking the car so the fuel creates waves. It might free the float.
Alternatively the + cable from the tank has been earthed along its length. Has the cable been pinched/corroded.

fuel drain light

Hi Mace!

With respect,I think you misunderstood me. The light on the dash that I was refering to was the Fuel Drain warning light. It came on along with the Battery Charge light a few days ago. From reading the post associated with the said problem it deemed nessasary to check the brushes in the alternator. This I did and found them to be worn out, hence the new brushes. Trouble is both lights are still on so my problem appears to be either with a completely knackered alternator or the battery. I think!!

fuel drain

have you tried to drain the filter to eliminate the fuel drain light problem. what are you driving fourtrak or sporty???

i wouldn't worry too much abo

i wouldn't worry too much about the fuel drain light, mine appears to glow dimmly most of the time, does the battery hold charge to start the engine Unknw if it does its ok . if yout meter only reads 11 volts accross the battery and there is enough power to start the car then there is something wrong with the meter . check it with another or try measuring another cars battery. the battery should read 12 volts with the engine not running. start the engine and run at idle speed the volts should hardly rise at all, when the engine speed is increased the volts should rise to a max of 14.4 then remain steady as the regulator cuts in to limit the voltage. are you measuring the voltage on the battery terminals or on the battery connectors? u could have dirty connections which can show full voltage when there is no current flowing but wont allow current to flow. u need to take apart and clean all the connections from the battery to the regulator and alternator. if all the wiring checks out can u get the cover off the regulator there should be 2 or 3 solenoids with contact breakers inside , the contacts can get dirty or stick shut, a piece of emery cloth will clean them.

Alternator, battery problem

Thanks for that Sir Richard.
I`m going to try another battery tommorrow and while I`m at it I`ll take the cover off of the voltage regulator to check the solenoids as you suggested. Will also check all the wiring. I`ll post an update when I`m done

Alternator?Battery? update

Good day Gents!

Just to throw something else into the pot.
Cleaned the contacts in the voltage regulator as suggested. Took the car out just now and noticed that the voltmeter in the dash started of reading just into the white. After a while the needle slowly crept up to just under the top of the white (18 volts). The fuel drain light and the battery charge light on the dash (which are both still lite up even after changing the brushes in the alternator) started to glow very bright. Again, after a while, the needle on the volt meter dropped down to just about half way (just into the white).
I`m thinking a dodgy voltage regulator!! Perhaps someone out there can confirm that it is a dodgy VR or tell me that I`m just being daft. Lol

Going up to 18v does sugest a

Going up to 18v does sugest a bad regulater.
The fuel drain light is to do with a filter in the fuel line, which reomoves water from the diesel. This used to be on the side of the chassis, under the grivers footwell on the F50's.
Having the battery light and the fuel drain light come on together sugests a fult with the lights them selves, rather than the things they are warning about. Change the regulator first, and see if the wrning lights start to behave, befor yoy do anything els. Jap electrics are renowend for easch componant effecting how 3 other things work (even if when the 3 things seam totaly unrelaited.

Any veiws expresed in this thread by me are purely from my own experience, and (sometimes) falible memory. Hope my comments help, but please don't take them as gospel.

Changed brushes and seems ok.

Thanks for that Kev! I have put new brushes in the alternator and all the warning lights now go out, so fingers crossed thats my problem solved. A quick question if I may. The brush holder is held in by a plate that is secured by two nuts. A wire goes under one of these nuts ( the top one). Am I correct in assuming that the stud with the wire on is live and the other stud would therefore be an earth? There is no wire on the other stud but when I put a test light onto both of these studs it lights up when the engine is not running. Is that right?? I thought that the wire that is connected to the top stud was the feed from the alternator to the battery. If that is the case, why is it live when the engine is not running?

The big wire runs directly fr

The big wire runs directly from altinator to battery. It is always live. It's the smaller wires used to creat the fild effect that get switched on/off by the ignition.

Any veiws expresed in this thread by me are purely from my own experience, and (sometimes) falible memory. Hope my comments help, but please don't take them as gospel.

Thankyou Sir Kev

Thankyou Sir! Your a gentleman and a scholar!


Fuel Drain

Have drained the filter, but the light is still on. I understand that the fuel drain warning light and the battery charge warning light are on the same circuit, which will explain why both lights are on.
Its a FourTrak F75!