Jump to content


Photo
- - - - -

Ignition Light


  • Please log in to reply
23 replies to this topic

#1 jonb_5

jonb_5

    Super Mini Mad

  • Members
  • PipPipPipPipPipPip
  • 575 posts

Posted 05 December 2008 - 12:39 PM

Hi,

I have had a problem with my ignition light not working.

While driving to the MOT sation today it came on and stayed on, only going off when the ignition was turned off.

Is this normal or what can i do to sort the problem??

Thanks

Jon

#2 lrostoke

lrostoke

    Crazy About Mini's

  • Members
  • PipPipPipPipPipPipPipPipPipPip
  • 6,845 posts
  • Location: Maybank, Staffordshire
  • Local Club: none

Posted 05 December 2008 - 12:44 PM

No its not normal..

Ignition light should only come on when ignition is turned on, once engine is running it should go off.

If its staying on its either

Wiring fault
slack or snapped fanbelt (snapped would also cause over heating though)
problem with the alternator.

#3 Ethel

Ethel

    ..is NOT a girl!

  • TMF Team
  • PipPipPipPipPipPipPipPipPipPipPip
  • 19,992 posts
  • Local Club: none

Posted 05 December 2008 - 12:47 PM

The ignition light should always come on when the engine isn't running. If it comes on when it is it means the battery voltage is higher than the alternator's. Check your fan belt tension first.

#4 2lrminivan

2lrminivan

    Mini Mad

  • Members
  • PipPipPipPip
  • 276 posts

Posted 05 December 2008 - 03:37 PM

The ignition light should always come on when the engine isn't running. If it comes on when it is it means the battery voltage is higher than the alternator's. Check your fan belt tension first.


it does not mean the batt voltage is higher that the alt it means the alt is not charging the batt. so the alt has stopped working or broken fan belt or wiring fault.
but it's prob the alt.

#5 jonb_5

jonb_5

    Super Mini Mad

  • Members
  • PipPipPipPipPipPip
  • 575 posts

Posted 05 December 2008 - 04:26 PM

Ok thanks guys, first thing i think i need to do is check the fan belt tension - how do i do this, it seems fairly taught and it spins when the engine is running??

Also the light only comes on when the engine starts up and is running, it doesnt come on at all when just the ignition is on, what could this be? Are there any checks thats i can perform???

Thanks

Jon

#6 tadleysimon

tadleysimon

    One Carb Or Two?

  • Members
  • PipPipPipPipPipPipPip
  • 1,454 posts
  • Local Club: basingstoke mini club

Posted 05 December 2008 - 05:21 PM

are you sure its the ignition light and not the oil light?

is it red or orangey/yellow?

#7 jonb_5

jonb_5

    Super Mini Mad

  • Members
  • PipPipPipPipPipPip
  • 575 posts

Posted 05 December 2008 - 06:07 PM

Hi,

Its definatly the ignition light, its red, does anyone know what i can do to check how to sort it, its just concerning me a little as its not working correctly, i dont really want anything breaking.

Thanks

Jon

#8 2lrminivan

2lrminivan

    Mini Mad

  • Members
  • PipPipPipPip
  • 276 posts

Posted 05 December 2008 - 08:02 PM

defo the alt as the light should be on with the ingition,i would have said check the bulb but it works so thats no good saying that lol.

#9 Dan

Dan

    TMFs Chief Doc

  • Mini Docs
  • PipPipPipPipPipPipPipPipPipPipPip
  • 20,779 posts

Posted 05 December 2008 - 08:17 PM

it does not mean the batt voltage is higher that the alt it means the alt is not charging the batt.


No, Ethel is right. If the lamp is on the battery voltage is highter than the alternator output voltage. That can happen for a few reasons. The alternator can be working perfectly, producing the correct voltage at its maximum output and still not charge the battery. Without an ammeter you can't tell whether the battery is charging or not.

#10 jonb_5

jonb_5

    Super Mini Mad

  • Members
  • PipPipPipPipPipPip
  • 575 posts

Posted 05 December 2008 - 08:33 PM

Hi,

I have a multimeter but not sure how to test it.

What do i need to do??

Thanks

Jon

#11 2lrminivan

2lrminivan

    Mini Mad

  • Members
  • PipPipPipPip
  • 276 posts

Posted 05 December 2008 - 09:00 PM

it does not mean the batt voltage is higher that the alt it means the alt is not charging the batt.


No, Ethel is right. If the lamp is on the battery voltage is highter than the alternator output voltage. That can happen for a few reasons. The alternator can be working perfectly, producing the correct voltage at its maximum output and still not charge the battery. Without an ammeter you can't tell whether the battery is charging or not.

so ive been a auto electrician (also sell alt as well) for the last 9 years. the alt will turn off the light when the output is correct. it cannot read the batt voltage.
if it does not charge the batt and the correct voltage is coming out of the alt then there is a wiring fault between the alt and the batt.


jonb-5
get the multimeter and put it to volts and connect the red leed to the big red lead on the alt and one to the body of the alt with then engine off and see if there is a 12v feed if so start the engine up and put the leed on the red wire again and see what the reeding is should be over 12.9-13.9 if its till 12v then the alt has had it.
then check the same on the batt.
the thing is if the light comes on when the engine is running then it is the alt as the light goes out to complete the circuit from the alt but if it stays on then the circuit is not complete inside the alt.

#12 lrostoke

lrostoke

    Crazy About Mini's

  • Members
  • PipPipPipPipPipPipPipPipPipPip
  • 6,845 posts
  • Location: Maybank, Staffordshire
  • Local Club: none

Posted 05 December 2008 - 09:00 PM

The fact the light only comes on when the engine is running and not when you turn the ignition on, points more to an alternator problem.

Regardless of battery voltage (unless its totally flat) the ignition light should come on when the ignition is turned on...yours isn't
The fact it comes on when you start the engine proves bulb is fine so really points to dodgy alternator..
Not sure how much to have one tested but I suspect probably more cost effective to get a new one.

#13 icklemini

icklemini

    Up Into Fourth

  • Traders
  • PipPipPipPipPipPipPipPipPip
  • 2,963 posts
  • Location: Northampton

Posted 05 December 2008 - 09:53 PM

When the ignition is switched on a power is sent through the ignition warning lamp this is connected to the rotor winding. This initial energisation is required so the rotor becomes an electromagnet, once the engine starts the rotor spins round and the magnetism causes current to be induced in the stator windings. Once this is happening the alternator is producing current, as well as supplying the car battery and the wiring inside the car, the alternator produces current to power the rotor winding (this connection is internal to the alternator), this means that there will be no voltage difference between the circuit through the ignition warning lamp (ultimately from the battery) and the voltage from the alternator.

So even though the circuit from the warning lamp is still connected to the rotor and is live, the alternators already putting power into the winding at the same value, the only way the bulb can come back on is if there is less power going into the rotor directly from the alternator than is available in from the battery.

For example if the battery was at 12V and the alternator was at 8V then 4V would flow through the warning lamp circuit causing it to glow slightly.

Glowing Ignition lamps on high load can also be due to bad earth on istrument pack circuits, and Lighting circuit.

Check voltage at battery:
battery voltage settled is 12.6 to 12.8 volts for a very good battery, 12.4 to 12.6 for an average battery.

Start car and voltage should rise from upto 14.4v (OK)
Check output of alternator (voltmeter from large terminal to earth) - 14.4v dropping to 14v on load
- earth points to check: alternator body, engine, body (voltage to be the same)

#14 jonb_5

jonb_5

    Super Mini Mad

  • Members
  • PipPipPipPipPipPip
  • 575 posts

Posted 06 December 2008 - 12:41 PM

Hi,

This morning I have tested battery with engine on and off, the same reading for both 12.5 ish volts.

Also tested the alternator with engine on and off, this was also the same around 12.5 ish volts, roase a little when i put the revs up.

I thought the alternator was knackered so i took it out and took it to a local car place who tested it for me, under a load of 20amps.

They said it worked fine, my problem being a dodgy fues or connection and if i couldnt fine it to bring it down to them??

What do you reacon, as i have proved the alternator works ok.

Where should i be checking for wire route etc??

Thanks for all of the help

Jon

#15 lrostoke

lrostoke

    Crazy About Mini's

  • Members
  • PipPipPipPipPipPipPipPipPipPip
  • 6,845 posts
  • Location: Maybank, Staffordshire
  • Local Club: none

Posted 06 December 2008 - 12:57 PM

Make sure the connections on the solenoid are tight..
Make sure earth straps are tight and in good condition..

With nothing switch on you want close to 14volts at the battery with the engine running.




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users

Mini Spares