19 replies to this topic

[Moggyton]

If im idling at about 1000rpm when i put the lights on the revs drop to about 800. This also has a huge impact on performance, very juddery when driving with the lights on whereas with them off, pickup is smooth and there is no judder. Any ideas? Thanks

[malynch27]

Whenever you use any of the pwered gadgets in a mini, especially lights, you will notice a slight drop in engine rpm. This shouldnt affect performance though. Hows the condition of your battery and alternator? If either one of these isnt performing up to scratch, when you turn on your lights etc...it could have an effect on the performance.

[Moggyton]

Whenever you use any of the pwered gadgets in a mini, especially lights, you will notice a slight drop in engine rpm. This shouldnt affect performance though. Hows the condition of your battery and alternator? If either one of these isnt performing up to scratch, when you turn on your lights etc...it could have an effect on the performance.

I went to replace the battery but the guy said there is nothing wrong with it, also had my alternator looked at and he said it was fine. i really dont know

[KernowCooper]

Voltage drop is what your describing, time to get the volt meter out and check the charging rate which should be 13.7/14.2v with the revs about 2000rpm with everything off, now put the light on and repeat the test, if you see less than 12.8-13v then check to fan belt then the battery for water (if not sealed type) and then its time to check the actual output amps of the alternator, check what model it is and see what its output is supposed to be 35/45/60a and go from there on your tests. Check all your battery connections and alternator and all earth straps for corrision and tightnessm and you should pinpoint the fault.

Is your ignition electronic or points? if all that checks out then its more time with the meter checking voltage feeds to the various components.

Edited by KernowCooper, 08 February 2013 - 08:17 PM.

[Moggyton]

Voltage drop is what your describing, time to get the volt meter out and check the charging rate which should be 13.7/14.2v with the revs about 2000rpm with everything off, now put the light on and repeat the test, if you see less than 12.8-13v then check to fan belt then the battery for water (if not sealed type) and then its time to check the actual output amps of the alternator, check what model it is and see what its output is supposed to be 35/45/60a and go from there on your tests. Check all your battery connections and alternator and all earth straps for corrision and tightnessm and you should pinpoint the fault.

Is your ignition electronic or points? if all that checks out then its more time with the meter checking voltage feeds to the various components.

ok thankyou

[Moggyton]

Is it possible it could be an earthing problem?

[KernowCooper]

One of my checks is for a bad connection which may have a high resistance which could then cause a voltage drop, its like having a green corrowded terminal somewhere

[tiger99]

I don't think that there is anything wrong except that your engine needs a routine tune, i.e. valve clearances, timing and carburettor. The alternator requires more power and torque to drive it when you apply a large electrical load, so if the engine is not in a perfect state of tune it slows. It would be very surprising if it was not so. You will not see this on an injection model, because the computer will compensate and keep the revs constant. On cars with an electric fan, even those with larger engines than Minis, it is perfectly normal for the revs to drop as the fan cuts in, applying a fairly similar electrical load as the headlights.

[Moggyton]

I don't think that there is anything wrong except that your engine needs a routine tune, i.e. valve clearances, timing and carburettor. The alternator requires more power and torque to drive it when you apply a large electrical load, so if the engine is not in a perfect state of tune it slows. It would be very surprising if it was not so. You will not see this on an injection model, because the computer will compensate and keep the revs constant. On cars with an electric fan, even those with larger engines than Minis, it is perfectly normal for the revs to drop as the fan cuts in, applying a fairly similar electrical load as the headlights.

Had it rolling roaded last week so i hope this isnt the case!

[Moggyton]

Still having this problem

[KernowCooper]

Ok time to start checking various voltages around the charging circuit and ignition system if your certain the cars set up ok, as by turning your lights on you put more demand on the alternator which should provide enough output so your cars other electrics should still function ok.

If you dont have a volt meter or your not up to speed yet on electrics then its either a mate who is or the garage, the key issue seems to be when the lights are on something in the ignition circuit does not like the voltage drop ( should not be when running a huge drop otherwise alternator is suspect)
Lights off engine runs sweet.

Volt meter time I'm afraid , you'll be looking at voltage to the + connection to the coil for one and depending on if its a 9v ballast coil or a std 12v run engine with lights on to induce the fault and check voltage and report back.

Be interested in what the battery voltage is running at 2000rpm with all the lights on.

[BenCoul]

Yeah, the rpm drop from 1000 to 800 is exactly the same as mine also. Affects my performance slightly, that's just the way they are

[KernowCooper]

I understand the bit about the revs dropping from 1000 to 800rpm thats just load of the alternator and normal as you say, what I dont get is the juddering when driving and a huge impact on performance reported by Moggyton? If like the wifes Mini 1000 lights on engine speed drops as described but drive off its as sweet as a nut, no juddering and not a huge impact on performance. Needs investigating on voltage drop to the cars electrics. Are you describing a misfire as juddering hence a huge loss of performance?

Is this car on points and condenser or electronic hall effect pickup? and you say its rolling roaded last week, but that could just mean timing and CO, are the plugs coils and plug leads all ok

Edited by KernowCooper, 20 February 2013 - 03:26 PM.

[Moggyton]

Think ill take it to a car electrics place by me. There is a huge drop in performance, car hardly picks up! thanks for the help mate

[Cooperman]

As they say 'oop north', "There's nowt for nowt".
When you turn the lights on you are using the engine to generate the power for all the lights, so the load on the alternator and thus on the fanbelt increases. This takes some power from the engine which then slows slightly. 200 rpm is quite a big drop, but not totally unusual.
It shows how much extra fuel is being used when driving with the lights on.