[Mk2] [NA] Speedo 60mph at idle...help!!

[GMLMR2]

Rev 2 import Speedo problem

This has been an on going problem for the past year, my Speedo is electronic and seems to do a lot of dancing around at first start idle, always happens in the morning, I go to start her up and the Speedo will shoot up to 60mph and drop down slowly but wont normalise until I start moving the only time it will normalize is if I put it into reverse but soon as I take it out of reverse it begins to rise when I haven’t started moving yet, but while driving it’s wobbling like a trooper and irons it’s self out after about a mile or so, its fine when driving and when the engines hot and idling the needle is fine, what I have noticed is that when the car is idling if I put the alternator under a bit of strain like put the head lights on or put the heater blowers on full blast the battery needle drops a bit and the Speedo needle raises to about 20 mph for a couple seconds then the battery needle rises back to normal then the speedo need returns to zero again.


I’ve run some tests on the battery and alternator as I got my suspicions that it might be a lazy voltage regulator with in the alternator but i might be way off

The battery is about 4-5 years old holds a decent enough charge and starts the engine fine, it reads 13.89 volts just after I have taken the car out and 11.83 volts when left for a day or so, while cars running at idle the alternator is pushing out 14.49 volts and under strain with all lights on, wipers going and all indicators on and heater blowers on the alternator is struggling and only pushed out 12.78 volts at idle and don’t get much better with revs.

Any help would be appreciated, I have been told that a rev limiter might be fitted but looked behind the clocks and no such thing exists all connections seem to be fine

[GMLMR2]

Lol well I’m guessing this has stumped as few with the no replies

Well after rigorous regime of testing,

It would appear the charging system and battery is a contributing factor, I filled the 2 cells up with water and fully charged it, this morning it’s held a good charge, refreshed all the wire connections to the battery, alternator, earth strap, needle was at 0mph at first start so getting there, I’ve managed to fix a power issue I been having for a while. The alternator isn’t being maxed out anymore when charging and when I pull on the electrics either by having the heater blowers on full or a movement of the steering wheel the Speedo needle is still at 0mph and headlights don't dim out when engine speed drops to idle anymore so that good.


I did notice after all the heavy rain we have had the alternator was dripping wet and so were the electrics around it so I’ve put in a handy funnel with a pipe on the end that I’ve channelled though to the bottom, this will redirect all the water out the way from the alternator and surrounding electrics, I moved the diagnostic port over to the other bolt hole so the funnel would fit in and room for engine moment and enough clearence for engine ventilation, yea ok it’s not pretty a bloody great funnel in the engine bay but who the fecks gona see see my engine bay other than me and £2.99 is cheaper than £200 for an alt and rotten electrics, lol water test I threw a bucket of water on the engine grill and everything was still dry :th:

[elijah]

Lol well I’m guessing this has stumped as few with the no replies

Well after rigorous regime of testing,

It would appear the charging system and battery is a contributing factor, I filled the 2 cells up with water and fully charged it, this morning it’s held a good charge, refreshed all the wire connections to the battery, alternator, earth strap, needle was at 0mph at first start so getting there, I’ve managed to fix a power issue I been having for a while. The alternator isn’t being maxed out anymore when charging and when I pull on the electrics either by having the heater blowers on full or a movement of the steering wheel the Speedo needle is still at 0mph and headlights don't dim out when engine speed drops to idle anymore so that good.


I did notice after all the heavy rain we have had the alternator was dripping wet and so were the electrics around it so I’ve put in a handy funnel with a pipe on the end that I’ve channelled though to the bottom, this will redirect all the water out the way from the alternator and surrounding electrics, I moved the diagnostic port over to the other bolt hole so the funnel would fit in and room for engine moment and enough clearence for engine ventilation, yea ok it’s not pretty a bloody great funnel in the engine bay but who the fecks gona see see my engine bay other than me and £2.99 is cheaper than £200 for an alt and rotten electrics, lol water test I threw a bucket of water on the engine grill and everything was still dry :th:

Quite an interesting post you have there. Well, even though no did reply or help you, it is a good thing that you were somehow able to solve your problem. Thanks for sharing this kind of info, it might come handy if ever I encounter this situation.