Can I ask some stupid questions.......

[fb2]

OK, so I'm pretty new to all this and my knowledge of car electrics is (although improving rapidly!) somewhat limited and so if these things sound silly please don't shout. I've done a search and can't find the answers but I'll admit I don't have a copy of the bible yet.

1) My volt meter seems to fluctuate quite a lot when the engine's running and varies with lights, fans etc, from 11V up to maybe 14V when at 70 mph (officer) with no lights or fans - is this normal? Not had a problem starting the car (touch wood) but have a sneaking feeling it's supposed to read about 13V the whole time.

2) My temperature gauge has (I think - I'm away from home at the mo) 50 - 90 - 110 marked with a white line at a bit of an angle above the 90 point and red a bit above this. Is the line 100 or 90? The needle doesn't seem to ever go above the line but, hey, it'd be nice to know.

Thanks

Duncan

PS Car's a 4.0 Griff

[The AJP Griff]

1)your voltage should not go as low as 11 Volts with engine running,and should always read well above 12 volts really(13.2 minimum ideally,though different people have different opinions on this figure).It sounds like your alternator is weak to me.
2)sorry i've no idea,as i dont have these gauges

[fb2]

Thanks for that. Is there any way to test the alternator?

Duncan

[spend]

I wouldn't bother about your gauge problems until you get a stable volt reading, most of the instruments use the same circuit so if the voltage is fluctuating its like having variable sensors...

As Mike says it does sound like your alt ~ rebuild kits are available if you like to play. I would just make sure the fan belt is good and the battery earth leads are good first (didn't you have corroded something problem recently?).

IIRC if you get a voltmeter reading of over 13.8v alt diode pack is foobarred - but I would round this to 14v as a rough & ready guestimate, so yours is marginal on this. Quick & easy to test at an auto-electricians, most will do it for free & give an estimate for rebuild / replacement.

Dave
ETA: forget to mention checking the :spitblood:100A fuse:spit: is making a good circuit - no cracks/corrosion. Gord fogive me please

Edited by spend on Wednesday 18th July 13:37

[The AJP Griff]

spend said:

IIRC if you get a voltmeter reading of over 13.8v alt diode pack is foobarred - but I would round this to 14v as a rough & ready guestimate, so yours is marginal on this....... Dave

You can see 14.5 on a new or freshly re-furbed alternator Dave,and that is fine,so i would say his high readings are not a problem.

[spend]

The AJP Griff said:

You can see 14.5 on a new or freshly re-furbed alternator Dave,and that is fine,so i would say his high readings are not a problem.

Brains gone Mike..... Yup over 14.8v is the common guideline isn't it?????

Dave

[The AJP Griff]

spend said:

The AJP Griff said:

You can see 14.5 on a new or freshly re-furbed alternator Dave,and that is fine,so i would say his high readings are not a problem.

Brains gone Mike..... Yup over 14.8v is the common guideline isn't it?????

Dave

It probably is something like that mate,but i've never tried to work it out to be honest.I've seen 14.6 on mine and that's great to me,as i understand the principles of volt drop etc

[fb2]

Thanks again all. Got the car out today and it although the voltmeter does drop down when eveything (fans etc) is on mostly it sits around the 13V level. Maybe I'm just being a bit 'new owner paranoid'?

[JoolzB]

fb2 said:

Thanks again all. Got the car out today and it although the voltmeter does drop down when eveything (fans etc) is on mostly it sits around the 13V level. Maybe I'm just being a bit 'new owner paranoid'?

My gauge usually shows around 11 volts even tho a multimeter shows higher, I just ignore it now.

[Uncle Fester]

Could also be the battery.
Mine was breaking down internally, although It still passed voltage drop test.
Start from cold, voltmeter reading 13.8V Keeps this reading for longer than normal.
After a while the current was heating the bettery internaly and it would begin to break down and go open circuit.
This seemed like a flat battery. Sluggish cranking, sensors getting low voltage and giving false readings and so on. The higher the ambient temperature the quicker it would happen.
The volt meter reading would then drop to about what you are experiencing.
Before we found the problem it damaged the alternator and so I ended up replacing both.
Fester

[fb2]

Is there any way to test whether this is what's happening or is just a case of trying a new battery? Obviously, if I can avoid damaging the alternator this would be good.