Alternator charging

[Peter Douglas Winn]

My '71 TR6 Carb. has consumed 3 Alternators in a short space of time.

No charging new alternator.

Battery flat, new battery, 18 months later battery will not recharge garage said charging ok.

 

3 regulators over a period of 4 years.

 

New Alternator.

New battery, shop checked and said it was ok

 

Now after the winter.

The good battery very low. After the engine starts the ampere meter charging goes off the scale and comes back within 1 min and after about 2 mins it is at the middle position.

In the past it when to full scale and took up to 1 hour to get back to the middle.

 

The headlamps do not change brightness when reving.

Questions:-

Has anybody had anything simular or has a hint as to what is going wrong?

Does anybody know where one can buy a complete diode pack like I used buy for my GT6?

 

The annoying is the car has worked for 15 years and without a problem even after putting in a complete new cable loom.

[PILKIE]

Hi.

I am not an auto electician,but seem to remember I had a similar fault on a 1970 Rover P6 2000tc I had when I were a lad.

Cooked 2 batteries before finding out what the fault was!

Have you checked that the alternators you are fitting haven't got a built in regulator? as you would then have 2.

You can either rewire to accept an ACR alternator,or fit a std non regulated one to suit.

Am sure having 2 regulators will mess things up a bit!

Also the flip to this,and this will cause problems as well,is fitting a non regulated alternator to a car that has had the in-line regulator removed and re-wired to accept an ACR alternator!

[Mike Collins]

Diode packs are readily available, try here http://cgi.ebay.co.uk/NEW-ALTERNATOR-RECTIFIER-FITS-LUCAS-ACR-15-16-17-18_W0QQitemZ260489241245QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item3ca65e629d

 

You need to check the existing diode pack for failed diodes with an ohmeter, it,s normally fairly obvious if one or more has failed.

 

The first check I would run is the alternator output voltage, it should be reasonably constant with rpm and load at around 14V, much less and the alternator is suspect. Significantly more and it's regulator may be be bad cooking the battery.

 

Time has passed on but my '73 Tr6 ate 2 alternators in it's first two years. At least alternators are easy to repair!

[Peter Douglas Winn]

As far as I know these are standard Moss Alternators for my model. I believe they have the regulator intergrated in the Diode pack. I have not chec<ked the Voltage output this time, as I was so happy to get the engine running on a flat battery, I just wanted to get the car back in the garage. About 2 years ago when I had a problem with the battery they checked the alternator and it gave these sort of voltages. What I don't understand is the Ampere meter going of the scale and then quickly going back to the middle position does this mean the Alternator is breaking down after a very short time. The reason for the flat battery could be the Alternator not charging and the Kenlow fan running on after the car is put into the garage.

[Mike Collins]

The diode pack is a separate component from the regulator, both under the rear casing. Changing the diodes requires a soldering iron, the regulator does not.

 

Your ammeter returning to a low state of charge could be a poor battery, poor contacts or an alternator problem. You need to check the alternator output voltage, at the alternator connector, at different loadings, turn everything on to make it work hard and monitor the voltage.

If it holds at around 14, it's probably not the alternator.

Check the voltage under the same conditions at the battery terminals, if there is a diffence look for high resistance contacts.

 

Is your battery discharged? If not, the ammeter behaviour is not unusual after start up, only a voltage check will confirm.

 

Was your battery left discharged in very low temperatures? That hastens the end of it.

[Peter Douglas Winn]

Pilkie

thank you for finding my mistake I should have said Voltage controllers (those little things at the back of the speedo)

How do I know if the problem is the diode pack or the regulator in the alternator? I now have in the garage 6 alternators!!!!!!!

 

Mike

When I can get to the car (flue bug at the moment) I will use some jumper cables get the engine running and do the voltage measurements at the battery. As I said before the headlights did not change their brightness with increasing engine speed. I checked the voltage at the terminals and then at the posts there was no difference and then I vaselined everything. When trying to start the voltage dropped down to 8 volts so I put the battery on charge. The car has been stored in a cold garage but always above freezing. I has been taken out for a warm and dryout run.

 

With respect to the measurement at the Alternator I have been hesitent to do it because I do not know what I am doing. I was told years ago do not run the alternator without load so how do I measure any voltages without taking the plugs off (contacts do not seem to be accessable). Secondly what should I be measuring? There are three contacts should I be measuring across the contacts or from the contacts to ground or or?

 

If the statement is true that an alternator should not be run on no load is an empty battery considered to be a no load?

 

I have look at the link and it is just what I wanted.

 

Once again thanks for the help perhaps I can return it someday.

[smizgals]

 

With respect to the measurement at the Alternator I have been hesitent to do it because I do not know what I am doing. I was told years ago do not run the alternator without load so how do I measure any voltages without taking the plugs off (contacts do not seem to be accessable). Secondly what should I be measuring? There are three contacts should I be measuring across the contacts or from the contacts to ground or or?

 

 

 

Peter,

 

Two of the three contacts are large,are common outputs and normally have hefty brown wires attached which connect to the battery via the starter motor, however one of them routes via the ammeter first. So measuring a good voltage at the battery terminals should be good enough.

The third wire, usually yellow and brown and thinner, connects to the ignition light and then by white wire to the ignition switch.

 

Stan

Edited March 22, 2010 by smizgals

[Peter Douglas Winn]

Stan As far as I can remember I have only 2 wires going to the Alterntor. A thick one (I think it is Brown) and a thin one. Madam will not let me get out of bed and go down to the Garage to check.

[Mike Collins]

The thick brown one is where you need to measure the voltage. In a system where all is well, the voltage will be effectively the same at the alternator and the battery positive terminal. It's when things are not going well that you need to measure at different points to identify connector problems.

Simple test, run the engine at 1500 rpm, headlights and heater fan on, what is the voltage at the battery terminal? Does it hold constant for a reasonable length of time?

 

If it's not around 14, or drops away let us know. I think we need to take one step at a time.

 

The way to check for diode failure requires an ohmeter and access inside the alternator rear case. Lets cross that bridge if we need to.

 

Running an alternator completely disconnected probably won't hurt it, but it won't develop any output as it has no excitation supply to get it going. Disconnecting it while the engine is running is what might damage it.

[Peter Douglas Winn]

Mike

Thanks, as soon as she lets me get to the garage, I will do exactly as you have instructed.

Peter

[smizgals]

Stan As far as I can remember I have only 2 wires going to the Alterntor. A thick one (I think it is Brown) and a thin one. Madam will not let me get out of bed and go down to the Garage to check.

 

 

I too had only one thick wire before I upgraded to a 45amp alternator at which point the single wire was inadequate to carry the possible high output current. So I added one to connect directly to the battery. What is the output of your alternator?

 

Stan

Edited March 23, 2010 by smizgals

[Peter Douglas Winn]

Stan

That's a dammed good question. Can I come back to you on that?

Peter

[Mike Collins]

Peter,

Look for a tag or engraving with 2 digits, followed by ACR, if it's a standard Lucas. The digits will probably be 16, 17 or 18, that's the bit that should identify the current rating.

 

Mike.

[Peter Douglas Winn]

So out of bed and down to the garage.

 

Battery voltage 12 volts. Voltage at alternator plug, thick brown lead, 12 volts!!!!! Starting, Battery 8 Volts.

 

Over night charge battery now 14 Volts. Starting battery 10.5 volts. Ammeter this time only to the middle of the charging range. Rev the engine up, no change in battery voltage. No change in headlight brightness but they are bright.

This makes me think the Alternator is bust.

 

Have looked for a tag with the type of alternator. Cannot find one but I seem to remember I needed a ACR 17. It was definately not a 15 because I remember thinking oh good I have not got the smallest charger.

 

I do know my Kenlow puts a large load on the battery in the summer when it tries to get rid of the residual engine heat when I switch off the engine.

 

Next move please.

[Mike Collins]

Glad you're feeling better.

 

 

 

17 ACR spec is 14V, 36A at 6000 alternator RPM. That current is a fair bit less than full scale on what I guess is a 50A meter. Ignition and fuel pump loads will reduce the current left to recharge the battery. So something around half charge scale after start for a time would seem normal.

 

Just spotted you're carbs so fuel pump not relevant.

 

"Rev the engine up, no change in battery voltage. No change in headlight brightness but they are bright."

 

 

Was the voltage at the battery posts still 14 at this point, with the headlamps on and 1500 rpm or so? If that's the case I don't think your alternator is faulty and we need to test your battery.

Edited March 24, 2010 by Mike Collins

[Peter Douglas Winn]

Mike I have a 2 year old 60 Ampere battery.

 

The headlights were bright with about 13 to 14 volts. The voltage did not change between engine running with lights and engine off with lights.

Mike this is one of these dammed things where you go round in circles and only when you talk to other people and they start asking questions you start to think logically.

[Mike Collins]

Peter, at 13V running, loaded I would think it's a bit low, 14 is more reasonable. If the alternator is struggling I would expect to see less voltage loaded than with the lights off.

 

"The voltage did not change between engine running with lights and engine off with lights."

 

That sounds a bit odd as your ammeter is showing a charge is it not? Is the ign light going out completely?

 

With the engine off and the battery loaded, it's voltage should start to reduce depending on it's condition.

 

Are you measuring the voltage at both battery posts or the clamps around them, or using the chassis as ground?

 

Going round in circles is right, I can't help feeling we're missing something.

[Peter Douglas Winn]

Mike

I will start thinking again.

Step 1. Engine would not turn over fast enough to start the car.

Step 2. Checked the Voltage no load 12 Volts.

Step 3. Checked the Voltage with starter motor turning very slowly 8 Volts

Step 4. Took the terminals off the posts and vaselined them.

Step 5. Measured Voltage between the posts 12 Volts.

Step 6. Measured the Voltage across the terminals 12 Volts when on the battery

Step 7. Charged the battery up somewhat with about 2 amp charge.

Step 8. Measured voltage at brown lead on the Alternator without the engine running 12 Volts then the battery 12 volts.

Step 9. Got the engine running.

Step 10. Switch on headlamps no change in the Voltage reading or brightness with engine running or not lamps bright.

Step 11. Ampere meter readings. After starting it was off the end scale and then after a short time went back to nearly the middle position.

Step 12. Charged the battery over night.

Step 13. Check Battery voltage about 14 volts.

Step 14. Started engine and Battery Volts dropped to about 10 volts then went back up to 13 to 14 volts.

Step 15. Rev engine up no change in the Voltage.

Step 16. Ampere meter readings Off the end scale after starting but very quickly back to the middle of the charging range this time.

Step 17. Put headlamps on no change in the voltage.

Step 18. Put Kenlow on as well very small drop in voltage.

Step 19. Rev engine up no change to anything.

Step 20. Left lights on switched engine off no change to brightness or voltage readings.

 

That is the end the serman.

[Mike Collins]

Petr, my head's going round.

 

Out of that lot, 13- for a battery just removed from charging probably normal.

14- sounds ok

15- possibly ok

16- sounds normal

17- fully charged battery, porobably ok

18- probably normal

19- I would expect to see a small increase from idle to high RPM, maybe the fully charged battery is masking it.

20- That confuses me, with a heavy load the voltage should drop gradualy. Does the ammeter show a discharge that changes with just lights, then fan and lights?

 

What are you using to measure voltage,is it accurate and how small a change can you read on it?

At 13V I would investigate the alternator, at 14 probably not.

 

If you doubt the alternator, start by checking the nine diodes with an ohmeter, you may have to unsolder the three wires from the main windings, if you are comfortable with that.

 

This link http://www.lotus-europa.com/manuals/misc/electrical/17acr.pdf is the Lucas repair sheet. Some of the info there suggests that failure of some diodes does not reduce the output much but alters the ign light behaviour.

 

I've just tried mine, engine off, battery voltage 12.4, lights on, gradually reducing to 12.2 over about a minute. Not been started for two days.

 

Mike.

[Andy Moltu]

When you had the battery checked - did they do a discharge test - effectively put a hefty load across it - see what happens to the voltage and check to see if any of the cells are fizzing? A lot of times they just stick a voltmeter across it without a load & wrongly declare it healthy.

 

Standing over the winter can well ruin a new battery - they gradually discharge & this radically reduces its life. It's vital to regularly recharge the battery when the car is not in use. Ideally disconnect it as radios & alarms are quite pernicious in discharging batteries. Or use one of the trickle or automated chargers.

 

The rapid return of the ammeter to the middle suggest a faulty battery (or a fully charged one)- a healthy but discharged battery will soak up a lot of current for a good while before being fully charged.

 

A charged but faulty battery (with a dud cell for example) will appear to rapidly recharge but won't have the ability to deliver on discharge.

[smizgals]

Peter,

 

For an ACR17 one brown wire should normally be sufficent.

 

From your symptoms I too would suspect the battery.

 

I guess your meter can measure current, so you can check if and how much the battery is discharging with the ignition off.

 

Disconnect the +ve battery cable and connect the ammeter between it and the +ve battery terminal. Note any reading and calculate the loss over a period, e.g. 1 amp will over 24 hours drain the battery by 24amps.

 

Stan

[Peter Douglas Winn]

Mike

Tomorrow I will go to the garage and take my digital voltmeter. I have been using a Gunsen's Analogue engine tester for the voltage readings. I will then see what happens to the battery when the engine is not running and I put a heavy load on. I will also see exactly what the Ampere meter is doing when the engine is off and when it is running. I have also thought about putting and old battery from my scrapped saloon and using a couple of starter cables from the wifes battery to get the TR started and then have a look. I am leaving the battery on charge all night. I do like the link, that the type of information is just down my street.

 

Andy you have given me a good idea, somewhere in the garage is a hydrometer for the battery. This will confirm you point about the dead cell. The battery has screw tops for topping up each cell.

 

The shop that checked the battery had a complicated Bosch battery tester with digital readouts and, and. I don't know how it worked but it looked professional and the shop is one of the biggest suppliers to the motor trade in Bavaria. potentially 13,000,000 customers.

 

Andy will you be a Harrogate? I'm trying to think where was the last time we met was it Denmark?

 

Stan if I remember tomorrow I will check to see if there is any current flowing.

 

Good night all.

[Peter Douglas Winn]

Hi!

New day new game.

On charge over night.

The battery now gives 13.48 Volts.

No leakage current.

Hydrometer busted through old age after the second check the first two were very good.

Starting with ignition shorted out for 8 secs 11.5 volts

Engine running about 700rpm 13.39Volts slowly going up to 14.25 Ampere meter in middle of the charging scale.

Engine running 700rpm lights on 14.05Volts -ve charging

Engine running 700rpm lights on + Kenlow 13.80 Volts more -ve charging. Over 1 min voltage slowly droping.

Engine running 700rpm only lights 13.5Volts to 14.0 Voltage rising very slowly charging in the middle.

 

Engine running 2000rpm 14.3 Volts.

Engine running 2000rpm lights on 13.95 volts constant amp in the middle of the scale.

Engine running 2000rpm lights on Kenlow on 13.68 Volts constant slight -ve charge

Engine running 2000rpm only Kenlow 13.7 Volts constant

 

My gut feeling says that everything is in the green area and the battery was so flat the all readings made no sense.

 

I you think the same please tell me. I still want to repair my other alternators and this has been a very good educationel exercise.

 

So it is now down to the shop and get a replacement hygrometer. The other one did quite well, I bought in in about 1965 for using on my 1st rally car battery (those days we had masses of lights and poor charging.)

[Mike Collins]

Peter, that all looks ok to me. As the battery is fully charged the ammeter will settle fairly quickly in the centre.

 

With mine on an 18ACR, at idle, the ammeter just about shows centre with the headlights on. Add the cooling fan and it shows a discharge until 2000 RPM or so.

 

How long does your Kenlow run after shutdown? A good battery should be able to cope with quite a long run on.

 

A battery capacity test might show that it's lost some by being discharged and cold. I'd be wary of very high discharge capacity tests, in the light aircraft world the compulsory cap. test seems to guarantee the end the battery. Leaving the headlights on for a while would be less cruel.

 

Enjoy driving it.

 

Mike.

[Peter Douglas Winn]

Mike, Stan and Andy

 

I have bought a new hydrometer and all cells are in the green area. In fact very green with the exception of number one that is good in the green.

Now if you want to know how to get the exhaust gasses of a USA carb motor down to 2.0. I can tell because I have just done it this afternoon. Tip it is the gubbings under the yellow plastic cover that causes the problems.

 

TTFN

Peter