Hi, my 1960 3.8L MK2 Auto has some charging issues I believe.
Static Battery Volts 12.97, when I start engine from cold & it's running on the auto choke I have 14.09 Volts.
Once the choke cuts out & running on normal idle of 900rpm it drops to 13.4 Volts.
If increase rpm the volts increase marginally up to 13.8 Volts
Fan belt is not loose.
The Amp Meter needle has always just flickered off vertical into Charge on idle
Is there a problem here?
For info, the Battery is 5 years old, car starts & runs OK.
R
Peter

 

Looks fine to me but is it converted to alternator, with negative earth, Peter?

I presume you're checking the voltage with a small, hand-held multimeter like most of us do, I have five multimeters gathered up over the years and they all read differently so I have little labels stuck on the backs that say 'point 65 volts low' or ' point 9 volts low' so when using them I have to mentally add it on to the reading to find the corrected voltage. One voltmeter, mounted under the speedo on a bike I regularly use, is a whole volt low right through the range. This is an easy adjustment to make when I need to drop a gear to get the alternator back on the right side of the battery voltage.

It took me several years to discover that new multimeters that I'd bought, because I felt the old one was maybe no longer accurate, was also untrustworthy. I hooked them all together in parallel on a decent battery and got my son in law, who's an electrician, to check them all against his big calibrated industrial one. This enabled me to mark mine up with their various plus or miinus corrections. I have no idea if his was exactly right either, (what do I trust?) but these adjustments have worked for me just about daily ever since.

Ray

 

Hi Ray, thanks for your reply.
Still running the original generator on negative earth.
Yes, just a handheld multi meter, but given your detailed response (ha,ha great love it), I think I'll change the battery in my meter
& then run the car down to the local garage & get them to check output with their meter against mine & then do just what you describe, record any variation.
Any clues on the amp meter lazy reading Ray?
regards
Peter

 

The values sound acceptable to me as well. Unlike yours, my ammeter always moved to mild discharge at idle, but my car idled much slower at 500 to 550 rpm.

 

Thanks Peter3442. Yeah, my Rev counter is playing up now which apparently does happen after fitting an electronic ignition recently ! Another issue to remedy.
Being automatic the idle prior to this change was more like 700rpm not 900 rpm as per the rev counter & I don't believe this has changed.
Peter

 

It may be the regulator that causes the ammeter to have a slow response, which is why I asked if it's been updated to an alternator. Alternators have the rectifier/regulator unit built in so have a much sharper response to demands for current as well as a superior charging rate. If it still has the old mechanical Lucas regulator., I expect, like me, its getting a bit tired and worn up. Even if it has it's points and settings attended to when needed, they don't respond like a modern electronic replacement does.

On my dynamo-equipped bikes, I put a new electronic regulator unit inside the old Lucas control box so it still looks original..

Ray

 

Is your multimeter digital or analog (with a moving needle)? I get some goofy numbers on my known good Fluke digital meter and I'm wondering if it is because the output of the regulator is so noisy. With the coils clicking in and out in the old style regulator the voltage (and current) are actually jumping all over the place. The battery should act as a damper but maybe not enough. Digital multimeters react very quickly (high sampling rate) and have no filtering or dampening while older analog meters are inherently damped (filtered) by the mass of the indicating needle.
Again, just a theory but I am going to bring home an oscilloscope and see what the voltage looks like. If it is noisy with an AC component, it may very well trick a digital meter. I'm also running a stock generator and regulator so it would be a good test.

 

Hi cdg66mk2, My Multi meter is digital & I put a new 9V battery in it.
Took the vehicle down to my local auto electrician garage & the tech checked the voltage & battery.
With engine running & off choke, my Multi meter read 13.2V while his Analog Meter read 14V, so can & now assume mine has a permanent error of minus -0.8V?
The battery checked out OK & holding charge be it 5 years old.
Peter

 

Just as an aside, I've had my MK2 3.8L since 1972 & it still has the original wiring (albeit a bit crusty in places) and ammeter.
Given all the hype (justified) re the amount of current sitting behind the dash & potential fire hazard I was thinking about replacing the ammeter with a voltmeter.
Some of the posts I've read suggest this mod if upgrading to an alternator while others say keep the car original, so I have second thoughts on this now.
I have never disconnected the battery in all these years after a run or being away for months on holiday and only disconnect it when working on something electrical.
Am I pushing my luck & should I start to disconnect the battery whenever the vehicle not being used?
I've had good luck with batteries & all have given me 5 years' service.
Peter

 

My '66 S Type is also quite original, Peter, has its original wiring and instrument, was converted to alternator by the previous owner and now with a new battery, solenoid and recon'd genuine Lucas starter motor. I used it weekly to keep the cobwebs out of it until the recent fuel prices skyrocketed so it's only been out on a couple of short trips in recent weeks. I, too, never remove a battery lead because it's hassle - I like to just get in and go. Busy, busy - no time for faffing about!

If it's a concern, you could fit an isolation switch somewhere convenient near the battery, either on the earth or live side (whichever is easiest) which stops having to wear a spanner and battery clamp out. I have three bikes that suffer from gradual battery draining through their voltage regulators so have fitted isolation switches under their flip-up seats to make life easier.

Ray

 

I bought a couple of Ctek battery maintainers a few years ago. I use one when I might not use a car for a couple of weeks. They seem to have been good investments as, so far, I seem to have avoided battery problems. Also, I don't buy cheap batteries any more - I used to and had several guaranteed for two years that seemed to consistently fail at two years and two weeks. The last batteries I've fitted are Yuasa from Halfords. Sometimes it's more convenient and cheaper to spend more.

If you disconnect rather than using a battery maintainers, remember to restart the clock on an old car or it may burn its contacts (if it hasn't already) and reset a load of stuff on a modern.

 

Thanks Ray & Peter I'll look into those suggestions.
R
Peter

 

A better comparison of the digital vs analog meter would be with the car not running. This would ensure that you have a nice, steady DC voltage. If the two meters read differently in this situation, then one is definitely out of calibration. With a very noisy source, I would not be at all surprised that they are reading differently.
I"m traveling for a few days but should be able to bring the o-scope hope this weekend. I'm curious to see what it looks like.

 

Just back on the hype with the ammeter point in previous post above, would installing a Fuse Link to the + or - side of the battery be a help should there ever be a short or overload?
Anyone done this?
Peter

 

These cars have several separate fuses in their systems which should cover all eventualities. On my older bikes I usually put a cartridge fuse between the battery and earth, just in case, but this can't be done on any bike or car that has an electric start because the loading is so high.

Ray