alternator?

[frank rabbets]

Hi

Got into LC and turned ignition on. Battery voltage was normal. Started engine OK but then all lights on dash came on and voltage dropped to circa 2 volts. Then after a few seconds everything OK with instant full voltage. If the alternator has a fault is it possible for the voltmeter to drop with both batteries fully charged? Done a search but can't find the specific answer.
Thanks
Frank

 

[Crispin]

Not the same thing?
search.php?keywords=all+lights+on+dash+came&terms=all&author=&fid%5B%5D=15&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search

Loose connection?

 

[frank rabbets]

No. I've read all those but nobody mentions what their voltmeter reads during the fault. I have thought about a loose connection but want to confirm that the voltmeter can drop to 2 volts with a faulty alternator but fully charged batteries. Then I would be happy to strip it and rebuild.

Frank

 

[Dave Docwra]

Could be worth checking the connections on the N/S battery.

 

[Chris]

Has it only done it the once Frank? Just wonder about sticking brushes.

Chris

 

[frank rabbets]

Only once Chris. Sticking brushes immediately came to mind but I was baffled why the voltmeter dropped to 2 volts with OK batteries. Nobody has been able to say if their voltmeter has dropped when their alternator has played up.

Frank

 

[Chris]

I'm pretty sure that mine didn't Frank. In fact I know it didn't. I drove home from Lincomb with no alternator (sticking brushes) and watched the needle all the way. Now, whether it ever flickered or anything when I first cranked it I can't say. But I don't recall it doing that. I have to confess that in terms of the charging circuit, I really do not know enough to advise you. I don't know if the reading when running is taken from the battery posts, or if it's a direct feed from the output of the alternator for example. What I wonder is, is there a switch over that goes from battery voltage to charging voltage when you turn the key. That could explain why it dropped and then came back up.
Easy enough to take the unit off and give it a fettle. A lot easier by the way if you take the air filter housing out first. If it's kicking out 14v then the expensive bit would seem to be working.


Chris

 

[frank rabbets]

Hi Chris. Thanks for that piece of info. I think perhaps the manifold heater was on at the same time as a faulty alternator. I shall wait untill it is cold, disconnect the alternator, start the engine and see what the gauge says? Flames?
I always keep an eye on terminals. earths etc and I don't think it is that.
Looks like this week it's alternator rebuild, power pump off, turbo pipe and manifold cleaned, tappets adjusted and then it'll be as good as ..............second hand.
Good thing I'm too old to go to work. I'm working harder now with all the projects than before.

Cheers
Frank

 

[Chris]

That's a busy weekend is that.

I'm leaving mine and going shooting instead. Need to spend a weekend standing up for a change.

C

 

[Jon Wildsmith]

Bit of an odd one that Frank, I don't think a faulty alternator could pull the voltage that low without doing a lot of obvious damage to the wiring. Were there any clicks that coincided with the lights going out again and the voltage reading returning to normal? Have the batteries been drop tested recently?

 

[frank rabbets]

Hi Jon

Didn't hear any clicks but it was all a bit quick.
The voltmeter shot back up.
Would a voltmeter on the batteries whilst cranking be a sufficient test?
I have had a battery terminal break inside before but then it did not recover.

Frank

 

[Jon Wildsmith]

It's a bit of a long shot but what I was wondering was if one of the batteries, the one that stays connected to the 12v circuit during starting (drivers side? can't remember) is faulty under load then during starting the voltmeter would only see the voltage that battery produces, until the alternator was up to speed or the change over relay clicked back again. With the latency in an analogue gauge that could seem like a second or two before it went back up to a healthy voltage? Seeing just a faulty battery would / should make the alternator shut down and that could explain the lights? But if both batteries and their connections are aok then this is a load of rubbish I have a mate in Engine lane that has a drop tester, on the end of the Smiths of Lye building, I'm sure if you called in Dave would stick it on for you.

 

[frank rabbets]

Thanks Jon. I will go over and get the batteries tested properly after having been on a good run to charge them up. I also think there is something in what you say re drivers side battery. I have had 2 failed batteries before and it was the drivers side both times.
Another factor is that I have been starting the 80 up several times a day and only going to Kidder to charge it up once a week.The starter did sound a bit slow before this happened. Now I have finished converting the side store to a garage that will be over.
Can you send me Dave's number please when convenient?

Frank

 

[Jon Wildsmith]

Can you send me Dave's number please when convenient?

Dave, at Motoweld, Engine Lane, Lye - 01384 892857

 

[frank rabbets]

Thanks Jon
Just checked the voltmeter before starting and it has dropped by quite a bit just standing so I will defo get Dave to look at them. Started it without alternator and voltage did not drop further. Reconnected the alternator and restarted the engine and after the heater had cut out the voltmeter soon reached maximum. So I might have a drain. Do you know what the max drain should be with and without the alarm on?

Frank

 

[Jon Wildsmith]

On yours anything more than about 0.03A is probably too high and it will probably be much lower than that. Is it the heater relay that turns into a smoldering mess on the 24 valve models? ISTR those being a bit of a problem.

 

[Andrew Prince]

Is it the heater relay that turns into a smoldering mess on the 24 valve models? ISTR those being a bit of a problem.

Starting to sound like a strong candidate as the source of the problem if Frank's is a 24v

 

[frank rabbets]

Thanks Jon
I'll check accordingly. Never had a drain problem before. Knowing my luck I've got duff batteries, loose connections. faulty alternator, bad earths and drains.
No it's been super reliable but does tend to eat batteries. The relay for the heater was changed under recall but I will check it.
What I cannot understand is the crap design of the front wings. There is no efficient upstand to stop water pouring off the bonnet then onto the inner wing edge and then into the engine compartment. It drains directly onto the manifold heater relay and other areas where there are electrics. I'm going to sort it asap.

Frank

 

[Dave2000]

Check the fuse connections near the battery, if the go bad this will result in a low volt reading. Remember you only need 1 amp to make the volt meter work.

regards

Dave

 

[frank rabbets]

Jon, if you're there, I've tested the drain and it is .045 amps [45 milliamps yes?]. There are 2 x 91 amp hour batteries so how long do you reckon before the car won't start!

Today each battery was reading 11.5 volts [engine not running] and each only dropped 1 volt during starting.

I'll get them tested tomorrow.

Frank