Current drain

alangj · Post by **alangj** » Sun Apr 08, 2012 6:40 pm

I have converted my 63 3.8L e-type to negative ground and alternator. Charges quite nicely, but I seem to have a key-off current drain on the battery. It is low and slow as it takes days to bring it down to no start power. Last night I noticed that the voltage regulator (not the dash one) stayed warm thru the night, so I wonder if that is involved. I did the conversion to alternator using the jumper wire from yellow to green wires, now tucked behind the alt bracket. I know it charges while running as the ammeter (I haven't switched to an in-dash voltmeter yet) shows charging under load and an attached voltmeter showed about 14.5V while running. Anybody else witha problem like this (or at least an answer)? I have competely reworked the car with all new harnesses and all the accessories (exc the clock, of course) work.
Also, does anybody know the correct way to connect the ammeter wires when I take it out to replace with voltmeter? My inclination is to just connect the two brown wires to complete that charging curcuit, but I don't want to make a mistake and fry all the wiring as these are two very large guage unswitched hot wires.
Al
1963 3.8L S1 e-type

Post by **Heuer** » Sun Apr 08, 2012 8:24 pm

Details on voltmeter conversion here: http://etypeuk.com/forum/viewtopic.php?t=166

How old is your battery? Our 911 has a 3 year old battery which only lasts 3 days if it is not on a trickle charger! Suggest you invest in a new one, preferably Exide or, if you are not averse to the colour orange an SBS40 (mine is 13 years old). http://etypeuk.com/forum/viewtopic.php?t=174

alangj · Post by **alangj** » Sun Apr 08, 2012 9:00 pm

Battery is brand new.
Al

Post by **mgcjag** » Mon Apr 09, 2012 8:37 am

Hi Al.....A good start point would be to pull all the fuses, leave overnight & see if this stops the current drain.....Steve

Post by **Heuer** » Mon Apr 09, 2012 10:03 am

Connect a digital ammeter in the battery circuit ans see what is being drawn. Then follow Steve's advice and pull the fuses one by one and see if the drain stops. Do you have an immobiliser fitted? With the ignition off the only current draw (a few milliamps) would be the clock. Disconnect the clock and you will be at zero.

noj · Post by **noj** » Wed Apr 11, 2012 11:07 pm

I came across this problem once but not on an E type, we checked the obvious for interior lights coming on etc the alternator was charging at 14v under load.
We disconnected the battery at night and it solved the problem of the battery drain and going flat,
all the relevant wiring and connections appeared good, in this instant the problem turned out to be the alternator itself even though we were getting good output readings 14v we fitted a new alternator and the problem was solved.

I am not saying this is the problem but worth a try if you know your battery to be a good one with the right AMP and you are sure of your wiring. I am still running with the old system.

alangj · Post by **alangj** » Thu Apr 12, 2012 4:48 am

turns out that the problem is probably in the voltage regulator (RB340 type). there is an ongoing current draw across the "earth" connection. it actually sparks a little when i touch the lead to it and the alternator doesn't heat up when it's disconnected. there appears to be a short in the regulator. may have to get a new regulator, or just put in a master electrical shut-off switch, like in my race car, that i turn off whenever i'm leaving the car for any period of time.
al

alangj · Post by **alangj** » Thu Apr 12, 2012 4:50 am

oops. make that "the regulator doesn't heat up when it's (the earth lead) disconnected", not the alternator.
al

christopher storey · Post by **christopher storey** » Thu Apr 12, 2012 7:51 am

Hold on ! how is it that you still have an RB340 when you have an alternator ? The RB340 is a current voltage control device which is suitable only for use with a dynamo. If you are using an original Lucas type alternator ( type 17AC or similar designation ) then there should be a 4TR type control , or if you are using a later type alternator then the control should be integral with the alternator . I think you need advice from an auto electrician of the old school to sort the problem out

alangj · Post by **alangj** » Fri Apr 13, 2012 5:24 pm

The old RB340 regulator is not truly an integral part of the system, as it no longer has the Field or the Ign light wires attached (they are jumpered behind the regulator and the cut-out relay is shimmed into the always-on position. the alternator is an aftermarket unit with an internal regulator. It's setup as per the installation instructions that came with the alternator conversion kit. I believe that the issue is that there appears to be an internal short in the unit as the Earth tab has current across it, which I doubt is right. on a schematic of the regulator, there is a resistor for that Earth connection, which may no longer be working, or, if it is, it is allowing a slow, milliamp drain even with the key off. i am guessing this is due to the always-on cut out relay. i may put a relay in that circuit with a switched source to obviate the problem.
Thanks for the thoughts.
Al

christopher storey · Post by **christopher storey** » Fri Apr 13, 2012 5:46 pm

The resistor on the Rb340 is on the underside of the unit , hidden away unless you detach the unit from the car. I do not want to be alarmist /over pessimistic but I really do not like the sound of all this : the problem with cvc units like the rb340 is that they can constitute a fire risk if they become either overloaded or permanently in circuit. ( I am assuming that it is still connected to the brown/yellow and brown /white wires which can carry unregulated and in some circumstances unswitched current) . At the very least you may be running the risk of frying the diodes in the alternator , but if it is actually continually passing current, which sounds to be the case , it may be more serious than that

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