| Author | Message | ||
     KC Saayman Frequent User Username: kc_saayman Post Number: 31 Registered: 10-2004 |
Dear friends The following relates to my 1948 Bentley Mk VI B108CF (the car has been converted to negative earth) I recently had the Dynamo overhauled, as it was not charging. The battery was also replaced. I now notice that the amps meter needle sits just off center on the negative side when the car is at normal speed. When I switch on the lights it drops even lower. I have turned it up a bit at the regulator, and the needle now sits just off center on the positive side at normal speeds, but sometimes goes to 20 amps, and then returns to just off center. This is without the lights on. I have tested the output with a voltmeter on the regulator, but battle to get a clean reading. It jumps around a bit, but seems to reach about 15,5 volts when on about mid throttle. The workshop manual says it can be as high as 16 volts, but I’m worried that it will overcharge and damage the dynamo, which is what seems to have happened previously according to my auto electrician. I have not tested the charging voltage on the battery terminals. Should I do that, and if so, what reading should I get. I would appreciate all comments about this. Kind regards KC Saayman South Africa | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 502 Registered: 9-2004 |
First thing is to of polerized the recon dynamo to - earth. However i suspect that the regulator may not be working correctly. It is a good idea to have the regulator set up after any confirmed dynamo failings due to over charging. When refiting the regulator make sure all the connections are in good order, paying specific attention to the earth conections. | ||
| Martin Cutler Prolific User Username: martin Post Number: 92 Registered: 10-2004 |
Hi KC, I had problems with my regulator, had it overhauled, and everything is now fine. If the generator has been overhauled, I would follow Patrick's advice and overhaul the reg as well. I have always tested the generator output at the battery terminals, not the regulator. Have a look at the archives for info when mine gave problems and the help I got. Cheers Marty | ||
| Martin Cutler Prolific User Username: martin Post Number: 93 Registered: 10-2004 |
Sorry KC, just looked in the archives myself, can't find it. Then I realised why, I had the problem in january 2001. Jim Bettison kindly sent me 2 pages from the manual, which show a cutting in voltage of12.7 - 13.3, and a cutting out voltage of 16.4 - 16.8 volts at 30 degress C. Hope this helps. With the use of modern technology I should be able to scan these pages in! Stay tuned! | ||
| Martin Cutler Prolific User Username: martin Post Number: 94 Registered: 10-2004 |
sorry KC, I can scan it, but can't get it under the 100kb limit, unless I can email the scan to you direct? | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 943 Registered: 4-2003 |
Please, do this one by the book. Guesswork and twiddling will only destroy your electrics. Use only an analogue meter: a digital one is useless. Best is an antique AVO (model 8 or 40 are ideal) or even a cheap one from an electrical hobby shop is OK.   | ||
| KC Saayman Frequent User Username: kc_saayman Post Number: 32 Registered: 10-2004 |
Thank you very much for that. I have the workshop manual, but did not realise I can’t use a digital meter. I’ll look for an analogue meter today. Richard, should I test the voltage at the battery, rather than at the regulator? My auto electrician has offered to replace the old regulator with a more modern type. Is this a good idea? (I don’t mind out of sight modern components if it will improve reliability) Regards KC | ||
| Peter Colwell New User Username: peter_colwell Post Number: 7 Registered: 3-2005 |
Experienced experts will have more specific advice than I, however I have had several vehicles with generator/regulator, one 1954, and one which I still own 1960. In both cases the regulator never caused problems, but occasional apparent regulator and odd problems were cured by fitting a new battery. In my view the voltage should be measured at the battery, as this is the 'bottom line', - so to speak, - in the system. Before changing anything I would try a new fully charged battery. Not very sophisticated I know, but it would not be the first time that a new battery has fixed problems that seem to have their cause elswhere. Peter | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 944 Registered: 4-2003 |
The reason I posted the pages of the manual is that they are quite specific. To set the voltage regulator correctly, the battery must be disconnected (terminals A and A1 disconnected at the regulator) and the voltage at the generator measured. The regulator should flick at 16.5 volts or so on a moving coil analogue meter as described depending on temperature (see the table). With generators, the adjustment needs to be done at least every 10,000km; also always adjust it when new brushes are fitted, and 3 and 6 months later. Any adjustment while measuring at the battery is just sheer tinkering. Depending upon charge, condition and charging mode, a good battery may read anywhere between 12 and 14.5 volts, but this is irrelevant when setting the regulator. RT. | ||
| Bill Vatter Frequent User Username: bill_vatter Post Number: 22 Registered: 9-2004 |
Richard is correct. It may seem somewhat odd that the regulator should be set with the battery disconnected, and also that the setpoint should be so high. When the battery is in the circuit the battery voltage has a strong controlling effect on everything, and it is not really possible to see what the regulator is doing. The aproximate 16.5 volts is the voltage limiting setpoint. After setting the regulator and reconnecting everything, you will find that with the battery in the circuit the voltage will be much less than 16.5. It will be whatever voltage is needed to push the current through the battery to charge it, typically around 13.5 volts. However in this situation, the voltage is not particularly meaningful. The ammeter will be telling you how much current is flowing and in what direction it is passing through the battery. At idle the current should be negative because at low speed the dynamo cannot generate enough voltage to charge the battery. At speed, with a fully charged battery, a very slight positive reading is correct. Note that some ammeters are not precisely on zero when there is zero current. With the car turned off note the position of the needle. That is the true zero reading for your ammeter. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 945 Registered: 4-2003 |
Thanks Bill. By the way, the battery is ideally located on these cars apart from vaguely possible damage from beneath. I have never had a battery last less than 12 years in my R-Type. Even then I replace them at the very first sign of weakness (ie the ammeter showing that the current settles down too quickly after starting). I put the long life down to the cool battery location and a correctly adjusted regulator. KC: please don't change the regulator. It is matched to the generator. You would open a can of worms in terms of current limits, cut-out and voltage regulation. The regulator and generator have never been weak points, and after 60 years of proof, why tempt fate ? A new set of Lucas USB105 brushes, a commutator slot clean-out/cut back, and a regulator fine tune are all that are needed from time to time. New brushes are cheap and available from any decent autoelectrician as they are still widely used on many trucks and buses. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 504 Registered: 9-2004 |
Just to confirm that what we are talking about is the voltage regulator fitted to your car,not the current control regulator which has a different method of testing and settings. One important check FIRST that i omitted was the checking of the fan belt corectly tensioned. I would also like to know what position the amp meter needle is in when the engine is run at say half throttle battery connected with the headlights, wiper, heater, fan on. | ||
| Arthur Francis Unregistered guest Posted From: 202.67.65.166 |
K.C., I had a voltage regulator burn out on an old Jaguar I once owned. After replacing it I got similar symptoms to you so I took the car to an auto electrician.After playing around with the settings he told me that the armature in the generator needed to be rewound or I would burn out another regulator.I followed his advice and had no more trouble.Was your armature checked when the generator was overhauled? (Message approved by david_gore) | ||
| Marty Unregistered guest Posted From: 220.239.60.186 |
Hi Richard, Mine is from the workshop manual, can I email it to you? I can't print out your scans, unreadable. Marty (Message approved by david_gore) | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 946 Registered: 4-2003 |
How large is the file, Marty ? I can handle about 8MB by email. Larger ones are best sent over Skype. If the resolution of my post is too poor, I can always split the pages and improve the quality by scanning smaller areas of the originals and reduce them still keeping each to the 640x480px/100kB accepted by this site. | ||
| Marty Unregistered guest Posted From: 220.239.60.186 |
Hi Richard, Around 600kb, but the site limit is 100kb. I somehow have lost my log on, hence the unregistered guest status (tried to update my email address). I am new to skype, but have sent you a message (didn't know Zurich was part of Canberra :-)) Marty (Message approved by david_gore) |
