Dynamo or Alternator

Post by **rayofleamington** » Fri Apr 25, 2003 10:52 pm

shall I go to Halfords?.

Was that sarcasm? Actually their parts are probably better than a lot of their staff.

Post by **Gareth** » Sat Apr 26, 2003 12:24 pm

Bull Motif sell alternator kits at around £60. Get 'em during the summer, though, because they may put them in an attractive special offer, 'cos nobody wants to use the lights, wipers, heater &c in summer. Alternators are a winter thing, aren't they?

Follows the reasoning behind buying soft-tops when it's snowing - reduced demand = better prices.

I have an alternator on Phyllis - mainly for peace of mind, along with the halogens, foglights, radio, heater, wipers &c. Seemed like a good idea at the time, and it only let me down once, when I lost the tension on the fanbelt.

Cheerio

Post by **PaulJohnson** » Sun May 18, 2003 2:52 am

Ok Everyone Part 2 of my problem.

Me & my Dad had the (1 year old ) Battery off last week, we check it over to see if it was ok, it was fully charged and everything was fine.

the car had done about 330 miles that week, so to my horror I was shocked when this morning 1am when stitting at some traffic lights the lights + speedo lights when dim when on tickover, they then when bright when we started to move off but apart from the lights on that was it.

Does anything need cleaning out or do you think my timing needs to be made quicker?.

Post by **Cam** » Sun May 18, 2003 10:49 am

If the lights went bright again, then it sounds like your charging system is generally OK. Maybe your regulator is incorrectly set, but I would not advise adjusting it as you maybe much worse off than when you started. Might be an idea to follow the manual and check that it's doing it's job properly.

Are you sure that the battery is OK?

You could adjust your tickover (not timing

) slightly as this will only affect the tickover charge and will do nothing for the general charging overall.

I would say that you might be doing too many short trips with the accessories on. Although you said that you did 330 miles, was it in the dark or were you in traffic a lot? if you were then you might be better converting to an alternator after all, as you might be trying to take more than the Moggy can give!

Post by **rayofleamington** » Sun May 18, 2003 6:04 pm

dimmed lights at tickover is normal with the dynamo, but if they nearly went out then then it would seem that your battery was getting very drained.
I have done some crappy commutes (55 minutes of traffic jam twice a day) relying on the dynamo, but I'm not prone to driving in London rush hour so these days it may be asking a lot.
On the other hand if your battery is getting too drained there may be a fault with the charging system but on the whole they are reliable.
Do you find it cranking over slowly? If you're going to charge the battery anyway you can check the capacity by diconnecting the coil and cranking - if it only turns over a handful of times then it's a problem - you should normally get 10 to 20 cranks (or more) if the sytem is healthy.

Post by **PaulJohnson** » Sun May 18, 2003 10:13 pm

Hello everyone.

Ok, ive just come back from the MMOC Barnsley branch annual rally at the Elsecar Heritage Centre.

with over 62 minors there I have had most of the owners look around my car, I told them about this problem and it caused quite a talking point.

One of the old-timers made my tickover go a bit faster, that made the headlight problem much better, however then I had problems geting into 1st gear.

Someone said I had a problem with my cluch as the pedel only come`s up 3/4 of the way up?.

2 owners have checked the battery & for faults and said that they can not find anything wrong?.

Post by **Willie** » Mon May 19, 2003 7:58 pm

The only way to check the battery for ability to accept and hold
a charge is to fully charge it and then take it to a centre where
they can do a 'discharge ' test. this takes seconds and will show
the state of the battery. A healthy battery and charging system
(dynamo) SHOULD show a glimmering red light at tickover. It is no
good just increasing the tickover speed to try to make up for a
faulty system because you will introduce other problems, i.e.
trouble engaging gears from standstill and possibly 'run on'when
you turn the engine off. The clutch pedal should be level with
the brake pedal in the 'up' position. If it isn't then you must have
a look at the operating mechanism underneath. There is a strong
return spring, and various bushes which may be badly worn.
There are also several pivot points and links which could be in
a bad state........all readily available and easy to replace.
( if you decide to replace the large rubber bush which sits in the
domed housing on the chassis leg then fit the modern plastic
replacement).

Post by **rayofleamington** » Mon May 19, 2003 10:40 pm

do a 'discharge ' test. this takes seconds and will show
the state of the battery.

True, but if you charge it first it'll only tell you about the battery, not the charging sytem (though I fully agree it's the best way to check the battery. It uses a high current flow and monitors the voltage capability - a high drop off shows a weak battery)

I still like my method to check the battery reserve on the car first if you're going to charge it overnight.

Post by **Willie** » Tue May 20, 2003 6:53 pm

Well Ray the problem with electrical problems is that there
are usually several possible answers to each fault. In order
to track down a fault the various possibilities have to be
eliminated. This chap doesn't know if he has a faulty charging
circuit,a faulty battery, a slight leak to chassis, or a faulty dynamo/
alternator. I would start with the battery discharge test personally.
Seeing how many times you can operate the starter is not exactly
high tec and includes the variable that the engine may be in a poor
state so that the compression load is low.

Post by **rayofleamington** » Thu May 22, 2003 12:13 am

Very true - many things could influence it, (and yes, shortcuts can lead to miss diagnoisis).
However you will get a false result from the battery test if the battery is nearly flat, so it's best to charge it.
However if you do charge it, how do you really know if there was a fault in the first place?
I guess you could do both tests (cranking test without charging followed by battery test after charging) to cover the charging system and the battery itself.

but it'll probably going to come down to the personal choice of Mr.J

Post by **Willie** » Fri May 23, 2003 7:40 pm

I did say"charge the battery and have a discharge test "done.
If the battery is pronounced fit then it is obvious that it was
not being charged on the car or there is a leak to ground. that
will at least have eliminated the battery itself.

Post by **PaulJohnson** » Mon Jun 02, 2003 3:16 am

Hello Everyone

Ive just come back from my dad`s in the dark and touch wood the headlights are not going so dim as they were before

And Why?. well today we fitted a new Distributor cap + the roter arm + fitted new HT leads ( same as a new mini one ).

Thanks for all your help.

Paul

Post by **rayofleamington** » Mon Jun 02, 2003 11:16 am

Hi Paul,
Erm.. Did you do anything else? Those parts shouldn't make an effect to the charging or current drain.
If the old parts were badly worn, you may have had an unstable tickover (occasional drop in the revs), but you didn't mention that.

Post by **PaulJohnson** » Sun Jul 06, 2003 2:16 am

Ok It`s Alternator or Dynamo question`s part 2
I was at our local South Yorkshire moggy branch meeting on Thursday when we got on to the subject of Alternator`s, my mate George said that he got one from a scrap yard for £3!!! and fitted it to his traveller, the only problem was that it is shorter than the dynamo so he made a bracket for the back to fit on.
Now then Is there any alternator`s out there that are the same size as the moggy dynamo to do a stright swap?.

Post by **Peetee** » Sun Jul 06, 2003 8:10 am

Making up a bracket is not always necessary. I used the exisiting bracket, an extra long bolt and an thick guage metal tube cut to length to fit between the alternator lug and the bracket. Allow for a couple of washers within this space. That way, by swapping them front/back you can be sure the alternator pulley lines up with the crank/water pump pulleys - they don't always!

Post by **Willie** » Sun Jul 06, 2003 3:37 pm

I bought a MINI alternator AND the proper rear mounting
bracket to go with it for £15 from a breakers. It is not
worth making your own bracket as if it is not strong enough
it will break sooner or later and ,if you think about it,this
will make the car undriveable!! (there will be no fan belt
drive to the water pump or fan).

Post by **Peetee** » Sun Jul 06, 2003 9:59 pm

Don't discount the home-made suggestion. It has proved reliable and cost me nothing. The tube is brass, 3mm in guage, and as fitted is in compression - therefore easily up to the task. Besides, around here Mini's are hard to find in scrapyards and the car that donated the alternator absolutely refused to give up it's bracket.
Truth is, I could have levered a bit harder but I feared for my knuckles

.

Post by **PaulJohnson** » Mon Nov 03, 2003 5:29 am

Ive Had A Alternator fitted a couple of weeks ago this was due to (olive) having new halogen headlights, front & back fog lights & a reversing light.

Now everthing was ok but yesterday the same problem happend as when i had the dynomo on when i was night driving and i stop the headlights + speedo dial lights go dim!

Post by **Willie** » Mon Nov 03, 2003 1:42 pm

It is no uncommon for the lights to dim slightly when the
engine is ticking over because if you are using a lot of
electrics at the time then they will be running solely on
the battery. This could be an early indication of a battery
which is not in top condition,how old is it? Mind you,an
Alternator should be producing a sizeable output even
on tickover, so make sure that the fan belt is tight enough,
(with an alternator you should NOT be able to turn the fan
by hand).

Post by **lowedb** » Mon Nov 03, 2003 8:44 pm

The voltage is likely to dip at tickopver, even with an alternator. The difference between charging well and only staying equal, is a coupl of volts, and since power is voltage squared, this can make quite a difference on lamps. A good test for this is a voltmeter. If at idle the voltage continues to drop, and is getting close to or below 12.0volts, the battery and charging system are supect, or you've got a big load. If at idle you stay reasonably constant, just above 12v, then your'e not charging the battery (with a dynamo you wouldn't) but things are generally OK.

For interest, the main reason alternators can give bigger outputs, the magnet rotates and the power comes from the static parts, so the brushes are only carrying the magnet current, not the output. A dynamo has static magnets and the output comes from the rotating bit, meaning big brushes. Just have a look at the relative sizes of the brushes on the two and you'll see what I mean.

Finally, again, modern alternators are VERY reliable compared to the Lucas 70ACRs and so on. The electroncis in these is rthe big cause of problems.