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Tickling a Lucas CVC unit

Submitted by paul_standeven on Sat, 04/08/2018
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Electrical

My dynamo charing system isn't.

I have tested the dynamo and it's producing output - 4V at idle, 14V at a rather fast idle. There's continuity between the dynamo D terminal and CVC D terminal, likewise F terminals. A and E (on the CVC.... ) have respective continuity as well. It all points to the CVC unit being faulty.

Is there anything I can do to the CVC unit to persuade it to do its job?

Paul

Submitted by robert_tuck on Sat, 04/08/2018

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Hi Paul, CVC units can be cleaned and points adjusted ,they are not as simple as they look but there are articles on setting them up .

Submitted by alan_osborn on Sat, 04/08/2018

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A O Services ie me sells an electronic regulator. it will do 6V or 12V in the one unit but you cannot change polarity, you need the right unit to start with.

Submitted by paul_standeven on Sat, 04/08/2018

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I'm having a look at www.matchlessclueless.com to try and get some tech advice. First idea is to try cleaning the contacts

Yes, I'm aware of the idea of converting to electronic regulator. I may do. One advantage of using a pair of Cyclon batteries is that I can wire it 6V or 12V

Paul

Submitted by robert_tuck on Sun, 05/08/2018

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I have to admit there is a certain satisfaction in getting old stuff to work,however the CVC is a crude device and if the cut out sticks can burn out the dynamo and set fire to things. I have a long forgotten memory of driving down Sydenham hill in a black sit up Ford Pop enveloped in smoke from a stuck CVC, normally the Feeble 6v battery would have just given up ,but I had stuffed a huge lorry battery in there somehow. Al's reg is recommended!!.

Submitted by alan_osborn on Sun, 05/08/2018

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Previously robert_tuck wrote:

I have to admit there is a certain satisfaction in getting old stuff to work,however the CVC is a crude device and if the cut out sticks can burn out the dynamo and set fire to things. I have a long forgotten memory of driving down Sydenham hill in a black sit up Ford Pop enveloped in smoke from a stuck CVC, normally the Feeble 6v battery would have just given up ,but I had stuffed a huge lorry battery in there somehow. Al's reg is recommended!!.

If it is a 'long forgotten memory' then you can't remember it......

Submitted by paul_standeven on Thu, 16/08/2018

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After lots of experiments, I had got nowhere... The dynamo output tests showed no output at all. That turned out to be dirt on the commutator. Now I have output, but the ammeter goes off the scale. I'm suspecting a voltage control issue in the RB107 control unit.

To add to the fun, the fuse blew as soon as I revved the engine. I have been having fuse blowing issues, but thought I had cracked that issue. I found a small area of exposed wire in the tail-lamp feed where it passes between the frame tube and tool tray.

Suggestions?

Paul

Submitted by george_phillips on Fri, 17/08/2018

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I too have fitted an AO unit to my ES2.

And Al is very helpful with checks and advice, provided you can cope with the acerbic wit!

George

Submitted by paul_standeven on Sat, 18/08/2018

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It turns out that the bike had multiple problems

The dynamo had stopped working due to dirt on the commutator. Repeated fuse blowing was due to a carelessly installed new ammeter,(by me) and there was shorting. Once I had that all fixed, I could run the engine up and check the dynamo output voltage. It was giving around 9V. It needs to be in the range 7.6 - 8.0 volts. Thanks to some original Lucas instructions sent to me, I could re-set the CVC unit, and I now have 7.9V.

If you have an accurate volt meter, you can check the output at the D terminal (it's actually easier to measure at the dynamo).. If you are looking at your CVC unit, there are two adjuster screws with lock-nuts. The right hand one is the voltage control. Turn it anticlockwise for fewer volts. Lock the nut when you have the right volts.

So it's sorted. Says I carefully touching wood.

The only expense was buying a volt and resistance meter. Lots of satisfaction on solving the problems and keeping it standard for now

Paul

Submitted by alan_osborn on Sun, 19/08/2018

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Just to keep you all on track, above by Paul checked the Dynamo output at 9V-fine but without specifying what was going down the Field ie normal regulator system (CVC or electronic)or D connected to F ie dynamo flat out, then this voltage is useful as an output indicator but not a point to worry about with regard to battery charging. Looking at it another way to get 8V at you battery your dynamo might need to be up at 9 or 10 volts to get it, ie you need what is known as 'head room'. So once we have a 'usable' dynamo output then the regulator needs setting for your battery charge voltage. The actual current into the battery is secondary as it depends on the state of the battery and perhaps the ability of the dynamo.

Acerbic wit.......I love sherbet lemons.......

Submitted by jonathan_newton on Mon, 20/08/2018

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Previously Alan Osborn wrote:

Just to keep you all on track, above by Paul checked the Dynamo output at 9V-fine but without specifying what was going down the Field ie normal regulator system (CVC or electronic)or D connected to F ie dynamo flat out, then this voltage is useful as an output indicator but not a point to worry about with regard to battery charging. Looking at it another way to get 8V at you battery your dynamo might need to be up at 9 or 10 volts to get it, ie you need what is known as 'head room'. So once we have a 'usable' dynamo output then the regulator needs setting for your battery charge voltage. The actual current into the battery is secondary as it depends on the state of the battery and perhaps the ability of the dynamo.

Acerbic wit.......I love sherbet lemons.......

Al Sortedmycharging maladiesrecently with aswift andacurate analysisof the playersin thechain and aspot ondiagnoisosofthe issue. Speedyresponseand plays fairwhen igot my plusandminusmixed up...

TheV-Regworks atreat :)

CheersALI'mmobileagain!!!

Submitted by paul_standeven on Wed, 22/08/2018

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Does anyone have the Lucas data for cut-in, cut-out, and max voltage for a 12V dynamo system?

I am wondering if I can set a Lucas CVC for 12V operation.

Yes, I am a perverse soul........

Paul

 



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