CV8 electrical charging system

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Barrie
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CV8 electrical charging system

Post by Barrie »

Now that winter nights draw on I’m experiencing what I believe is a problem with the newly overhauled electrics on my CV8

Last week I had a two hour run and was luckily only about 200 yards from home when the throttle became unresponsive at low speed and I felt a stall was imminent . A quick jab on the accelerator pedal and the engine picked up power again until I had to slow down to a crawl and the same thing happened several times with each hesitation becoming longer and requiring a longer press of the accelerator. When I was outside my house it all died. Prior to that the electrics were under a heavy load with engine fans, heater fans and headlights on.
It seemed to me that the battery had drained as the headlamps were very dimmed.
I immediately put the battery on charge and the following day all was well. I tracked down and rectified a faulty boot light switch which had intermittently been draining the battery.
It’s still left me a little wary of what’s going on and so today I went for a one hour run and no repetition. Except.................as I was putting the car away I decided to put all the electrics on (Lights, HRW, Heater, Fans) and as I increased the load the indicator flasher progressively slowed to a halt.
So my question is: what’s causing this apparent lack of charge?
I had initially thought it was the boot light remaining on but the replacement alternator should have covered that.
All ideas gratefully received.
“Even in a time of elephantine vanity and greed, one never has to look far to see the campfires of gentle people." Garrison Keillor
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Martin R
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Re: CV8 electrical charging system

Post by Martin R »

How old is your battery? Could it be failing?
If you're getting 14v at the battery with the engine running, it should be charging.
"Something" might be pulling more amps than it should, which of course could drain the battery quickly but, I'd have thought if it's draining that quickly, it'd blow a fuse first.
The other thought is check the tightness of the battery terminals.
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Barrie
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Re: CV8 electrical charging system

Post by Barrie »

Thanks Martin.
The Battery is about a year old. Is there a away of testing it without a proper battery tester? I have a multimeter.
The battery meter in the cockpit shows 14V on charge which drops to 11v on tickover.
Terminals tight.
“Even in a time of elephantine vanity and greed, one never has to look far to see the campfires of gentle people." Garrison Keillor
Wallace
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Re: CV8 electrical charging system

Post by Wallace »

Check the battery voltage with the mutleymeter on idle to see if the gauge is correct. Then try at 2500 to see what Reading you get. Don't forget to make sure Mutley is set to DC Mr Bond.
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DPP
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Re: CV8 electrical charging system

Post by DPP »

The best way to test a battery with just a multimeter is by using the starter motor to discharge the battery.

Disconnect your coil HT lead to stop the car from starting, then with your meter across the battery crank the engine for 15 seconds observing the voltage which should not drop below 9.6V.

Better still measure the capacity of the battery, I use one of these as it gives an accurate reading of battery health.
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PeterHume
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Re: CV8 electrical charging system

Post by PeterHume »

Hi Barrie
It sounds like your alternator is not charging at idle with the voltmeter reading 11 at idle and 14 at higher speeds. The most likely cause for this will be the alternator needs to be running faster.
First thing to check, is drive belt tight?
Secondly,, you mentioned alternator is new. It might pay to double check it's suitability in that it needs to commence charging below normal idle speed. This could be a problem if the alternator is built for something like an earthmoving machine designed to run at a constant high engine speed versus the wide range of engine speeds encountered in a car.
The third possibility is the new alternator might need a smaller diameter pulley to increase its speed, but again, you would need to verify the speed range of the alternator to ensure it is still within its speed range at max engine revs.
Regards
Peter
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Barrie
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Re: CV8 electrical charging system

Post by Barrie »

Latest:
The battery is only holding 55% of its capacity
The alternator is older than I thought and despite being 90amp does not supply enough to charge headlamps, fans, heater etc at tick-over which surprised me.
First step is a new battery and the retest the alternator as the weak battery may be effecting it.
Peter, the belt tension is correct and I don’t think the pulleys are to blame although, as I mention above, the alternator only starts charging above tick-over. Sometime the alternators need a small LED light attached to draw a current at low rpm but I though my alternator didn’t need that. We’ll soon see once its retested after a new battery is fitted.
My memory is faulty as the battery and alternator are quite old. In fact Wallace fitted the alternator when the old one conked out just as we arrived at a Jensen Rally maybe 8 years ago. I don’t suppose you remember anything about the alternator Wallace?
Thanks to all for advice.
“Even in a time of elephantine vanity and greed, one never has to look far to see the campfires of gentle people." Garrison Keillor
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Re: CV8 electrical charging system

Post by RichardGibson »

Hi Barrie
Had issues with my Interceptor Mk2 alternator a couple of years ago, it packed up on the way to the International in Malvern, it was night time and raining so all electrics were on and the voltmeter was bouncing about like a yoyo.
I bought a new 90A alternator and all was OK.
The following year (last year) on the way to the International in Hull, I stopped for coffee at Gretna Green and lo and behold on trying to start again the battery was flat. The car was jump started and ran well. I put this down to the hammering the battery had taken the previous year.
I bought a new battery in Carlisle. At this point I discovered that the battery in the car was a size too small, I now have a correctly sized battery and again all was well.
This year, about a couple of months ago I was driving through Huntly on my way to having some work done on the car when again the voltmeter dropped to zero. My destination was only 10 miles away so I carried on. When I reached my destination the battery was flat and the car would not start.
As the alternator was newish I phoned Robey's, where I bought the unit and they asked if I had replaced the voltage regulator.
I have to admit that I had assumed the voltage regulator was built into the alternator, but it is not.
I replaced the voltage regulator and whoopee the voltmeter is now reading 15 volts, even on idle.
The alternator was shot by the way and the battery was incorrect.
Just a thought.
Regards
Richard
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Re: CV8 electrical charging system

Post by Wallace »

I remember a case of serious overcharging on that day at the International and that was just paying for the replacement as yours had no output!

What voltages are you seeing at idle and 2500rpm? Are the headlights wired for four low beams? If I remember, there was a huge Halfords battery on there that may be in warranty.
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