Tech help - mk1 Golf alternator/battery

[Dave_Q]

Hi all, 

 

GF's car has started, erm, not starting. 

 

mk1 golf 1.8 carb.

 

Will go if jumped or battery charged but then will not always restart after being driven.

 

I have poked a multimeter at it, but I believe my meter is inaccurate.

 

I'm getting 13.7v across the battery with no load dropping to 13.2v with a load.

 

However, the meter gives me 13.2v across the battery with engine off.

 

It gives me 1.63v from a new AA battery so is clearly over reading.

 

Have tried reading from the alternator when running which gives me 13.9v, which I think is a reasonable drop to the battery?

 

However, if the meter is over reading by 5-8% then the 13.7v is only about 12.6v, which is just barely within the HBOL specs but far from the 13.5-14v I'd like to see.

 

So any ideas? Other than getting a new multimeter.

 

Battery? Voltage reg on alternator? The battery is a Bosch silver which is 2-3 years old.

[Dave_Q]

P.S. I promise we're not pineapple botherers.

 

We actually un-lowered it.

[red5]

Change battery in your multimeter - 1st sign of low power is over-reading.

 

The try a static (all off) battery reading - then a running no-load, then a running full load.

 

Got access to a ammeter?

[vulgalour]

Get another multimeter first and see what happens?  Worst case scenario is that you have two mulitmeters.  Dirty connectors, duff alternator, dodgy battery are all possibles.  Has it got an aftermarket radio?  It may be leaking electricity.

 

"Pineapple botherer" gave me a giggle too.

[Asimo]

 

It gives me 1.63v from a new AA battery.

That may well be fine. The 1.5v is a nominal figure and different battery types give different terminal voltages.

 

When you say doesn't start, what sort of not starting? No point in worrying about the battery if the engine turns over at an acceptable rate.

If it cranks but slowly, Measure the voltage between the engine block and the negative terminal of the battery, should be very little even with the starter cranking. Anything much over .5v and you have an earthing problem.

 

These starter motors can have sticky solenoids, which will give you nothing but a click when you turn the key.

[Sloth in a bowl]

Also use the multimeter on a car that you know is happy to confirm that it throws out correct numbers.

 

But I would agree that earthing and solenoids are the most likely culprits.

Lastly I have had the situation where the starter doesn't always engage the ring gear properly, put car in high gear move it a foot then try the starter again (once back in neutral of course).

[Dave_Q]

The no start is just nothing when turning the key. 

Dash lights are on but no turning, clicking, nothing. Jump or battery charge gets it going.

Did try rocking in gear and hitting the starter with a hammer.

 

Even based on my dodgy readings the alternator is only putting out approx battery voltage with a load.

 

Am thinking of getting a regulator and a new multimeter tomorrow.

 

Needs fixing before Monday.

[Asimo]

Check the alternator is earthed. They are mounted on rubber bushes and have an earth strap "across" a bush. These break sometimes when belt is adjusted or get left off / fitted wrong if alternator is replaced.

[Guest Tony Hayers]

But I would agree that earthing and solenoids are the most likely culprits.

Lastly I have had the situation where the starter doesn't always engage the ring gear properly, put car in high gear move it a foot then try the starter again (once back in neutral of course).

 

Jesus Christ, are you Samson? Push a car, IN GEAR!

 

Agree about earth straps, funny things that easily get upset when covered in crud.

[Dave_Q]

I don't believe there is an earthing strap on the alternator, it is hard mounted via metal to metal mountings on this car.

 

Anyway I measured the voltage between the terminal and casing of the alternator and was only 0.2v higher than across the battery.

[Asimo]

ok, but that could still be true if the alternator earth connection had failed, that is why you should measure between the alternator frame and the engine and / or battery neg.

[Barry Cade]

I've come across a few dodgy VW ignition switches. When it doesn't start, put 12v straight to the spade terminal on the starter with the ignition on, with the car in neutral..... rule things out methodically...

[Dave_Q]

I'm sure you were all on tenterhooks waiting for the outcome of this, but I think it's fixed.

 

New regulator and belt and a clean up of the +ve wire from the alternator to battery and it's giving 14.2v at the battery.

[Dave_Q]

I've come across a few dodgy VW ignition switches. When it doesn't start, put 12v straight to the spade terminal on the starter with the ignition on, with the car in neutral..... rule things out methodically...

 

Eleventy internet mechanic points for this man.

 

All seemed well for a couple of days but then wouldn't go again yesterday. Battery voltage good and starts with 12v direct to solenoid.

 

I was going to replace the ignition switch but the unloader relay still seems to be working when the key is turned to start. 

 

According to HBOL for this to happen the switch must be working.

 

So is it the switch, or an early 90's immobiliser related wiring issue?

 

Place bets now.

[dollywobbler]

Oh, you've got an immobiliser? That could well be the culprit. Had a similar problem with my Rover 400 'bubble'. A friend who was good at auto-electrics kindly removed it for me. Problem solved.

[Jimcit]

I had a similar issue on mine (same car / engine) turned out the alternator bushes had worn down to nothing - they come off with a couple of screws (bit fiddly, but can be done with alternator in place) but easy enough to check and cheap to replace.

 

They looked like this and should have been about 2cm long:

[Dave_Q]

Have replaced the regulator assembly already, probably unnecessarily.

 

Immobilectomy is complete, luckily the fitters put it 6in from the ignition switch for extra security.

 

 

Wires were super easy to trace, just need to pick up something suitable to reconnect it all in a factory fashion in the morning and should be ok.