Dynamo or Alternator

Post by **Kevin** » Tue Nov 04, 2003 12:31 am

modern alternators are VERY reliable

So would an alternator of a later proper Mini make for a better conversion or are they still the same

Post by **rayofleamington** » Tue Nov 04, 2003 1:22 am

The voltage is likely to dip at tickopver, even with an alternator.

Is that true? I've not messed with alternators much as it usually takes only 5 seconds to see if the regulator is working or not.
Therefore I never really tested for any difference under load.

An alternator will create a torque on the fanbelt to match the current consumption and should keep a constant voltage at tickover. When measuring volts at the battery, the voltage will reduce as you turn everything on, due to the voltage drop in the wiring between the alternator and the battery, but I thought it should stay constant at the alternator - or does this reduce?

On modern cars the alternator is a big problem as the varying torque demand from the alternator can bring the engine close to stalling at tickover (the engine is calibrated on a very fine line to meet emmissions standards and therefore has negligible torque reserve)
On a Minor, there's usually plenty of reserve torque at tickover.

My Volvo had 2 faulty Alternators - one was Bosch and the other was Paris-Rhone, so it seems not just related to Lucas.

Can the alternator's regulator be damaged by the user (eg somone messing with the wiring or bad wiring?) I wonder if a short circuit could cause the regulator to fail, or if it is voltage spikes from olde worlde vehicle elctronics.
Of course - vehicle electronics can and will sometimes fail,all by themselves due to poor quality capacitors etc.. or due to poor design and lack of adequate heat sinks etc..

Post by **Cam** » Tue Nov 04, 2003 10:56 am

poor quality capacitors etc

Most of the capacitor failures are due to items being specified which are far too close to their operational limits. I think Amstrad started this trend and that's why most of his stuff was always failing. Actually a lot of components nowadays are spec'd far too close to the limits, especially ICs, ASICs, resistive elements etc. Which is why the old stuff lasts a LOT longer than the new. But it's a cost cutting excercise and modern stuff has a short life anyway thanks to our 'throw away' society!

My alternator does reduce it's output on tickover. I have a voltmeter on the dash so I can see what's happining at all times. If I have my lights, wipers, heater and radio on when waiting at a junction then the needle drops to about 13 volts from 14 ish. (meter not terribly acurate) but it does drop noticeably.

Post by **lowedb** » Tue Nov 04, 2003 1:45 pm

Alternator maximum output output reduces as rotor speed reduces. The output power available is related to how fast you are turning the magnet inside the coils, how powerful the magnet is (determined by the current generating the field) as well as how thick the wires are and how much current the rectifiers can handle.
When the output is less than maximum, the regulator reduces the power of the magnet to limit the output voltage keeping a nice constant voltage at it's output. But once the demand for current exceeds what is available with maximum current in the magnet, the output voltage reduces. This is much more likely to happen at idle when the maximum available is at it's least.
Most of the problems on older alternators are the semiconductors, and technology for producing them has changed a lot. You can damage the electronics if they are not well protected. Connecting the battery bacwards, jump starting from a 24v truck, disconnecting the battery when the alternator is running can all produce nasty spikes which upset unprotected alternators. Saying that I had an alternator die because one phase of the stator corroded through. Shouldn't mount alternators where salty water can get at them!
An alternator from a later car ought to be better but you should be thinking of '90s cars to see any real improvements in reliability.

Post by **MikeTrav68** » Mon Nov 10, 2003 2:20 am

Alternators are inherently more reliable than dynamos - the alternator has slip-ring connections rather than the multiple pole brush connections required of a dynamo. Having said that, the early mini Lucas alternators (ACR series) do suffer from old semiconductors and I have has failures. But you will find modern alternators with the same mechanical form e.g.: fiesta, which you can use with the mini bracket. One of the problems is the push on connector, so if you can be bothered to convert to a bolt connection ('O' terminal) this is better. Halogens are not much different from sealed beams in terms of current - it's the key off drain that will stump the battery: alarm or radio. Or winter driving - lights, wipers, rear screen heater + idle, a dynamo can't keep up. If this has worked for you for a while on a dynamo then clearly your use pattern is OK. If you want to check - disconnect your coil. You should be able to crank for a minute continuously. If not, think about repair (new bat probably) or upgrade. Lead acid battery life is a function of discharge state: if it spends most of the time discharged (maybe dynamo on short winter trips) it will do 200 cycles. If it's mostly charged, it will do 2000. I use a low current (1A) voltage regulated 13.8V mains charger connected to my classics when not in use - very good to extend battery life.

Post by **Kevin** » Tue Nov 11, 2003 12:04 pm

So Mike you would reccommend a Fiesta alternator, from which model and does it have a type code.
How difficult is it to convert to a bolt connection and what about the pulley, and how do you go about it as I know nothing about alternators.

Post by **MikeTrav68** » Wed Nov 12, 2003 12:18 am

I will try and identify mine, at a guess '85 escort 1.3, but if you wander around the breakers yard you will find there's only a few makes and formats on all cars. Anything that has the following spec will do:
1) Single 'v' fanbelt. Obvious really, don't go for a double fanbelt, it will have too much torque, and poly-v is out.
2) Two 8mm(5/16) pivot bolt mountings, one off the front casting and one off the back. Note that the alternator is often two- fixings even when only a single long pivot bolt is used.
You will find this on later minis, metros, fiestas, escorts and who knows what else! I guess Metro is good because you get the rear bracket for A-series, adjuster bracket and fanbelt. The datum fixing is the one on the water pump (like dynamo). You can put a straight edge across the pulleys to see if they are in-line. Odds are they will be, otherwise use a file or washer. The rear pivot bolt uses a roll-pin and so self adjusts. Use the lower thin adjustment bracket from mini or metro, and the slightly shorter fanbelt.
3) Easiest electrically is to use an alternator with the two 3/8 and single 1/4 spade connections in one moulding. Just plug in the dynamo wires - the two 3/8 are both current out, the smaller one is charge lamp. Don't forget to reconfigure the dynamo regulator connections as per MMOC technical tips. Or you can remove the regulator and just connect the lights, ignition key and battery out wires together, but then you have to work out how to keep them insulated from the car body. Current for the wires is over spec, but only for five mins after you start the engine.
Optionally on the alternator:
3) Pick an alternator already on the right side. You can remove and rotate the rear alternator casting but it's easier not to.
4) Fit a 40-50A cable direct to battery +. As mentioned, I think bolt connection is more reliable but it depends upon the alternator you get.
I've tried to be detailed so it sounds complex, but really it's not.

Post by **rayofleamington** » Wed Nov 12, 2003 5:30 pm

only a few makes and formats on all cars

Don't forget to read up on the power output. They can vary from 30 Amp to 70 Amp output... This will sometimes be displayed on the ID plate.

Post by **MikeTrav68** » Wed Nov 12, 2003 11:12 pm

Good point Ray. Avoid the temptation to go as high as possible, above 55A you'll spend your time readjusting the belt. The high current ones are for high current electrical systems, like interior fans that take 30A (easily possible today) not 5A like a minor. In a minor, most of the current goes to the battery. For a few minutes after start it will take 25A, 10 mins later it will be 5A. 30A alternator will do that.

Post by **lowedb** » Thu Nov 13, 2003 8:00 am

There's an even bigger range of outputs available than you might think. Range Rovers ten years ago had 110 amp alternators, I know of some machines that are spec'd as 140 Amps but will produce up to 190A in the right conditions. And no, they aren't for commercial vehicles! They are water cooled, though. I should think they would stop an A series dead at maximum output, but when the cooling fans on those cars take 70amps at full tilt, you need that kind of output

Post by **rayofleamington** » Thu Nov 13, 2003 1:48 pm

later minis, metros, fiestas, escorts

30 to 70 Amps covers pretty much this type of car already mentioned..
but yes, large executive vehicles will have bigger ones. Executive cars have a lot more electrics to drive - however biger than a 70 Amp alternator is rare as they get very expensive. Some manufacturers even fitted 2 alternators as a cheaper alternative to a >100 Amp version..

My only reason to comment on power output it is for safety!! If you fit a 70Amp alternator it is capable to burn out 50 Amp wiring (and burn out the whole car).

I would guess that a 30 or 40 Amp version is more than enough for a minor with heated rear screen, stereo etc..

Post by **MikeTrav68** » Sat Nov 15, 2003 10:43 pm

So checking up, I actually used the one from a Montego 2.0l. This is right sided, but uses a poly-v belt. I swapped the pulley for a single V. It does use spade terminals (the connector was good) but I ran a high current cable from both large terminals direct to the starter solenoid. The point about bolt terminals is you only need one and they don't corrode, I used a bolt type on my Volvo. The rear bracket is Mini, and I forgot to mention the ignition coil, which looses it's bracket on the dynamo: I used the mini bracket under a cylinder head stud.

On part numbers, this is A127 (the Lucas number). The secondary number is current, -55, -60 (mine), -70 are available. The best donor car would be a late mini (>1988?) since you can get the brackets. Minis also used type A115 and A133, slightly lower current older designs but with the same fittings. Avoid the Lucas ACR series, reliability of regulator and rectifiers is not brilliant. Metros of the same age used the same 3 types and again you can get the A-series brackets. For another source of A127 alternators you can use MkIII Escorts of the 80's, which probably means also Fiestas since they shared CVH and OHV engines. Ford rebadged these but they still have 'Type=127'. Pinto Sierras used A127's but they are left sided so you have to unbolt the top, turn it round and drill the adjustment thread out to a hole. DOHC sierras use A127 with a bolt connection adapter. Bosch (K1 series) and Motorola (26xx) are equivalent parts.

As mentioned previously, finding an alternator to fit is not difficult! Happy charging

Post by **PaulJohnson** » Fri Nov 21, 2003 3:23 pm

Iam afride you have lost me on this amp talk?.

All I can tell you is that (olive`s) fan belt is tight = will not move by hand and when the moggy place in Manchester fitted my alternator because i had some hallogens fitted + foglights they added 2 more fuse`s boxs, so I now have 3
Could this be why my whole lights are did when Iam at a stop?.

Post by **Kevin** » Fri Nov 21, 2003 4:55 pm

Where did they put the extra fuse boxes, I would have thought the foglights would have been OK with a relay.

Post by **PaulJohnson** » Tue Nov 25, 2003 12:21 am

Kevin, The Moggy place at Manchester said it was better to have more fuse box`s because all the power coming out of one will keep blowing a fuse.

As for where they are the box`s are all next to each other at the top left in the engine bay.

Best Wishes Paul.

Post by **salty_monk** » Tue Nov 25, 2003 2:20 pm

Maybe I'm biased but for a good/excellent anything I'd avoid Halfords like the plague!

In my opinion it's a place where you buy over priced product from people who know absolutely nothing about them & don't care anyway... There must be one or two good ones though I guess.

Post by **PaulJohnson** » Tue Nov 25, 2003 5:29 pm

Your Right There !!!

If I need a new Halogen bulb it would cost me £9.99 from Halfords!.

I didsome shoping around and found a electrical place in Derbyshire that will sell one for £3.47.

Best Wishes Paul

Post by **iwant1** » Thu Feb 05, 2004 8:32 pm

I was wondering how to tell if my car is negative or positive earth, sounds daft i know, but it should be a quick thing to find out...shouldnt it. Ben

Post by **rayofleamington** » Thu Feb 05, 2004 8:40 pm

iwant1,
If the negative (-) terminal of the battery is connected to the body then it is negative earth.
If the positive (+) terminal of the battery is connected to the body then it is positive earth.