Battery charging, is this normal ?

Post by **Heuer** » Fri Oct 09, 2015 6:20 pm

Well, you can lead a horse to water but you can't make him scuba dive!

Swapping the ammeter for a voltmeter takes about 30 minutes; adding the digital meter takes about the same provided you have the correct Q-max cutter to hand

288gto · Post by **288gto** » Fri Oct 09, 2015 9:01 pm

Alty Ian wrote: ......... popped out to the garage for fuel and to pick up the curry in it!

I still havent recovered from the shock that everything now works and couldnt resist just giving it a few beans at the lights, just WOW

When does Stephen get to go clubbing in Manchester in it then?

Great to see you got it sorted and look forward to you coming to visit in it.

Simon

Alty Ian · Post by **Alty Ian** » Sat Oct 10, 2015 6:18 pm

Spoke too soon again. My electrical troubles continue

Took the car for its first shakedown run today, 15 miles each way with a 2 hours stop before returning. After about 13 miles the rev counter started behaving strangely and was reading around 500 rpm when the engine was doing about 1500 rpm, hesitant at first then eventually just hovered around 500 and stayed like that. I checked all the connections and when I tapped the glass it would affect it a little. This has been fine whenever the engine has been run until now, I suspect its the gauge rather than the rev generator. Are they easy to fix? When I stopped I noticed the cooling fan was running even though the gauge read about 80 C. What temp do the otter switches activate? It was a cool day and I never stopped at all (country lanes) and the engine definitely wasn't very hot. During the first run the ammeter was slightly charging and water and fuel gauges worked ok. When I turned on the ignition to return home, I realised the dashboard stabiliser had failed again! Tested when home and it has failed, thats the 2nd one to fail. When home I tested the voltage and it was 13.84V from the battery, however I noticed it fall to around 12.5V within about 2 minutes or so. Is that normal?

I am wondering if the alternator is generating too high a voltage? I am hoping the 4TR hasnt packed in as well again, I need to test it again.

A few other minor issues as well but all things I can easily fix.

Gfhug · Post by **Gfhug** » Sun Oct 11, 2015 8:44 am

Ian, if you still have the older RVI tacho you may wish to convert to RVC, I sent mine away to Spiyda https://www.spiyda.com/magento/index.ph ... board.html
Returned promptly.
It may be a solution if you don't solve it through other means.

Geoff

christopher storey · Post by **christopher storey** » Sun Oct 11, 2015 11:39 am

Geoff : Ian's tacho is generator driven , not the S2 impulse type . The first thing to check is the generator output, which should approximate to 10volts AC for every 1000 engine rpm. Sometimes the drive dog may slip out of engagement which could be what has happened here. What is certain is that the main electrical system has no influence on the AC generator tacho at all as there is not connection between them. The battery voltage dropping after shutting down is quite normal. Although 12.5 volts is slightly low - the ideal is about 13 volts DC - it would not worry me

Post by **Heuer** » Sun Oct 11, 2015 3:04 pm

Rev counter - As Christopher says the tachometer has its own private circuit and supply and is not influenced by the battery or alternator voltage. The biggest and most common problem is the magnets get weak meaning the generator does not output 1v/100rpm no matter how fast the engine is turning. Best cure is to find a good original (they were used on all XK engines of the period) or convert to electronic (details in the Upgrade Forum). The reproduction generators are prone to failure but if you cannot find a good 'un they may be your last hope. Try M&C Wilkinison or Ken Jenkins for a good original.

Fan - the Otter switch has a fairly broad temp range. If you want accuracy buy the (Mitsubishi) switch from Fosseway at ?35. Also bear in mind the temperature gauge is for 'guidance only' - they all vary in accuracy as does the manifold sensor. Once you get to know your car it will not be an issue as all you are really looking for is a change in temperature reading from normal (whatever that may be) rather than an absolute value.

Alty Ian · Post by **Alty Ian** » Sun Oct 11, 2015 3:26 pm

christopher storey wrote:Geoff : Ian's tacho is generator driven , not the S2 impulse type . The first thing to check is the generator output, which should approximate to 10volts AC for every 1000 engine rpm. Sometimes the drive dog may slip out of engagement which could be what has happened here. What is certain is that the main electrical system has no influence on the AC generator tacho at all as there is not connection between them. The battery voltage dropping after shutting down is quite normal. Although 12.5 volts is slightly low - the ideal is about 13 volts DC - it would not worry me

Just checked and the battery is 13.01Volts the day after. I ran the engine and the voltage is 14.79V at about 1500rpm so the 4TR still works. The dashboard stabiliser has 0V output :( I took the tacho apart and found a small short between the red cable and the back of the dial, separated it and tried again but now nothing at all. I will test the tacho next and the generator and see which has failed. EDIT; The generator has failed. Ordered a new one.

Post by **Heuer** » Sun Oct 11, 2015 3:35 pm

VR - You can make an electronic VR for a couple of quid. It only uses two components, readily available from Maplins, and you can fit it in the original housing: viewtopic.php?t=5011&highlight=voltage+regulator.

Tach generator - unplug the generator wires and connect a voltmeter. Run the engine and you should get 1v/100 rpm i.e. 30volts at 3,000rpm. If you don't it is the generator.

Alty Ian · Post by **Alty Ian** » Wed Oct 14, 2015 6:17 pm

It goes on !!!

The rev generator has failed, no voltage from it when engine runs. Ordered a new one. Just received my 3rd dashboard voltage stabiliser, guess what,.. it didnt work either. The whole batch is faulty and SNG are investigating. I am seriously thinking now of making my own as suggested by Dave.

Mark Gordon · Post by **Mark Gordon** » Thu Oct 15, 2015 11:45 am

If the rev generator has suddenly failed, it could be a faulty drive dog that attaches the shaft of the generator to the notch on the rear of the camshaft. The drive dog can wear which keeps the camshaft from supplying rotational power to the generator. A new one is pretty easy to fabricate by using the original as a template or, as in my case, just reversing the drive dog and putting the unworn edges against the camshaft solved the problem.

Alty Ian · Post by **Alty Ian** » Thu Oct 15, 2015 3:03 pm

Good idea Mark, I havent removed the old one yet to see why it failed so that maybe an option. Thanks.

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