tr4 Alternator Swap for Dynamo

[rcreweread]

Hi everyone

 

Would appreciate some advice over what is probably a really stupid question but here goes!

 

When swapping a dynamo for an alternator, I'm aware you can retain and use the old regulator as a junction box, but in doing so, do you have to remove it's internal working parts first.

 

If so, are the parts easily removable and such that you can re-instate the control box back to full functionality, or do you effectively ruin it in doing so.

 

Also, what are the likely consequences if you don't - a daft question on the face of it but not if you may have been stupid in the first place!!!!

 

I have searched and read the threads I can find on this, but I can't find the specific answer to my question.

 

Any advice much appreciated

 

cheers

 

Rich

[peejay4A]

When I did mine I rerouted the tracks on the underside of the box and to make sure that none of the internals affected things I disconnected those too. So for mine it was a one way trip.

[John Morrison]

Hi Rich,

 

what's your thinking?

 

Pete's correct if you use the control box as a junction box during a conversion, then it is kaput for going back.

 

If you havn't done the job yet, and would like the option of reversal sometime hence, then save the control box, especially if you know it's good, and use something else, chocolate blocks would do,

 

john.

[Don H.]

There are dummy control boxes in the market, IIRC. The idea is to have the needed internal connections made with no added guts, in a box that looks otherwise normal on the outside.

 

Another option is to find a kaput control box and gut that, rather than destroy a good one.

[rcreweread]

Thanks guys for input so far.

 

I would like to keep the engine bay looking as original as possible, hence I've fitted a dynamator and wanted to retain the control box.

 

The instructions which came with it had a wiring diagram to show what wires to connect where on the control box, but said nothing about removing/disconnecting the internal working parts.

 

It was fitted like this and this will no doubt explain why I have so far cooked two new batteries as I am constantly charging at 15-20 amps - I may have an old regulator which I can cannibalise rather than wreck a good one so I'll have a hunt for it tomorrow and reconnect and see if the charging is behaving itself at last - what a dickhead!

 

cheers

 

Rich

[peejay4A]

Rich,

I'd try making the connections but not using the control box to see if that makes the problem go away. If it doesn't you might have a problem with the dynamotor.

[littlejim]

I modified my regulator when the alternator went in.

Thought it could be turned back to original with a big dob of solder across the gaps.

I bought a replacement one to put in the bits collection, in case the next owner wanted to convert back to a dynamo, and wasn't into solder dobs..

[peejay4A]

That looks very much like mine.

[RobH]

You don't need the control box really and there is no need to use it as a junction box if you don't want to - but if you want the engine bay to look original that might seem a bit odd with no wires going to it. When I fitted an alternator I did what Don and the others suggest by cannibalising an old control box and additionally used the empty shell to house a fuse-box for the extra circuits I have installed like the cooling fan (picture attached).

 

There are Dynamator wiring diagrams on these sites for negative earth and its worth checking yours is wired as shown.

http://www.autoelectricsupplies.co.uk/image_uploads/negearthdynalite_large.jpg

http://www.autoelectricsupplies.co.uk/image_uploads/neg_earth_with_dummy_control_box_large.jpg (with dummy control box)

if you have positive earth this is the diagram

http://www.autoelectricsupplies.co.uk/image_uploads/pos_earth_with_orig_control_box_large.jpg

 

Barring incorrect wiring, its difficult to understand why you have continuous charging if the Dynamator is working properly - there is really nothing in the old control box which could cause that to happen even if it was left connected as per the first diagram.

 

Rob

Edited May 2, 2015 by RobH

[MRG1965]

Hi Rich, I did this very upgrade earlier this year. To test if the dynomator is faulty, simply join the three large wires together and join the the two small wires together, which is what the use of the junction box is doing. If you still have the problem, must be dynomator, but given the voltage regulator is in side, its difficult to see what wiring problem you may have.

 

Mark

[rcreweread]

Update on progress today - found another control box in my pile of spares but it was a Lucas B90 Exchange unit at one point according to the sticker on the back and in better nick than the one on the car so neither is going to get cannibalised.

 

I therefore took Pete's suggestion and simply connected the wires together to see what happened - well it has made a big difference - charging at first start up was about 15-20 amps, then rapidly fell to a constant 2.5-5.0 amps after about 20 mins of driving, so miles better than it was.

 

I think the battery may have been cooked by the previous over charging as it doesn't seem to want to hold a charge so I wonder if this is what is causing the constant charging, albeit it is only a few amps - am I right in thinking that in normal circumstances with a fully charged battery, the ammeter should be reading zero?

 

In the meantime, I will try and source a knackered unit which I will modify as per littlejims suggestion although I like Robs suggestion of an extra fuse unit inside it!

 

Thanks for everyone's advice so far

 

Cheers

 

Rich

[rcreweread]

Hi all - a bit of a result last night in that I won a control box on fleabay for 99p so don't mind cannibalising that when I get it!

 

I measured the battery voltage, with the engine not running, at 12.68 volts after a 20 minute drive - does that sound like the battery is knackered - what is a typical standing voltage for a good battery?

 

As always, any advice appreciated

 

cheers

 

Rich

[Lebro]

If it really has been seriously overcharging at 15 -20 amps then the electrolyte may have lost a lot of water due to it bubbling away as H & O2.

If it is the sort of battery which can be topped up, then worth checking. After this the best test is to slow charge from a mains type charger overnight, then see what voltage you have. It the battery is still spinning the engine over reasonably fast, then it will probably recover.

 

Bob.

[rcreweread]

Bob - it's an Exide battery with removable plugs over the plates and electrolyte levels all look OK so I'll try it later on when the weather improves and see how well it turns over after yesterdays charging and run.

 

Fingers crossed

 

cheers

 

Rich

[RobH]

The voltage you quote is about correct for a nearly fully charged battery Rich (table below), but the voltage doesn't tell you anything about the battery capacity - and it is capacity which can be lost by overcharging if the plates heat and distort. Also things are still not right if you are getting a continuous charging current of 2-5 amps while driving for 20 minutes - it should fall to zero pretty rapidly, say after five minutes or so depending on how much cranking was required. Once you have done what Bob suggests and you are sure the battery is OK, if the continuous charging still continues it might be something else causing that.

 

When you turn the ignition on first before starting, does the ammeter show a small discharge? If it does not your ammeter is wired incorrectly - it should be connected only to the battery at one end. If anything else is also connected at that end (e.g. the ignition feed) the meter will read that load current as a charge in addition to the actual battery charging current and that will give you a continuous reading while driving.

 

charge voltage
100% 12.7

75% 12.4

50% 12.2

25% 12

 

 

Rob