Tacho and Charge issue.

Talk about the E-Type Series 2
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DazbodS2
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#1 Tacho and Charge issue.

Post by DazbodS2 » Tue May 15, 2018 8:54 pm

Hi Guys,

I have a 1970 S2 coupe with, I believe, ballast ignition. On a run at the weekend the Revcounter stopped working, at the same time the battery ceased being charged (according to the dash voltmeter) and the red dash light has illuminated. I had this problem a year or two ago but the fault apparently rectified itself having been dispatched to the garage that maintains my car for investigation. The car otherwise runs fine and all other circuits appear to work ok.

Any thoughts appreciated

Thanks

Darren
Darren - 1970 S2 FHC Signal Red.

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ralphr1780
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#2 Re: Tacho and Charge issue.

Post by ralphr1780 » Wed May 16, 2018 7:43 am

Darren, you can start by checking the ignition relay.
Ralph
'69 OTS + '62 OTS - Belgium

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Nigel GT
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#3 Re: Tacho and Charge issue.

Post by Nigel GT » Wed May 16, 2018 8:12 am

Hi Darren,
I had the same problem, it was a melted fuse holder which makes the fuse contact loose, so i would look around that area for loose contacts, blown fuse etc, from memory RH fuse block 3rd down.

Nigel

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politeperson
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#4 Re: Tacho and Charge issue.

Post by politeperson » Wed May 16, 2018 8:48 am

I wonder if it has taken out your cooling fans as well. Yes fuse block holder. I changed all mine the other day.
Its true, but Enzo never said it
Too many E types
XK120 SUs

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angelw
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#5 Re: Tacho and Charge issue.

Post by angelw » Wed May 16, 2018 10:57 am

Darren Wrote:
I have a 1970 S2 coupe with, I believe, ballast ignition. On a run at the weekend the Revcounter stopped working, at the same time the battery ceased being charged (according to the dash voltmeter) and the red dash light has illuminated. I had this problem a year or two ago but the fault apparently rectified itself having been dispatched to the garage that maintains my car for investigation. The car otherwise runs fine and all other circuits appear to work ok.
Hello Darren,
If the voltmeter is still alive and showing the battery condition, but that the battery is not being charged, it is unlikely that the ignition relay (3AW) has anything to do with the issue. The ignition light circuit does nothing other than show that the alternator is charging or not. In its unconnected state, the contact between the Earth and WL terminals of the 3AW is normally closed and therefore, the ignition light will be illuminated when 12volts is applied when the ignition switch is turned on.

The ignition light is extinguished when the alternator starts charging and applies a current to the AL terminal of the 3AW (from the alternator) (this forces an open contact between Earth and WL). Accordingly, the ignition light will only come on when there is no current being supplied to the AL terminal of the 3AW, or the switch mechanism associated with the AL input has failed in the 3AW (a bi-metal coil). However, if it were the 3AW that has failed, the function of the alternator would not be affected.

Have the alternator tested to confirm it is operating correctly. If it is, then I would look at the Alternator relay, mounted on the Left Side Inner Mud Guard (just forward of where the battery is situated). Failure of this relay will stop the alternator from functioning.

Regards,

Bill

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DazbodS2
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#6 Re: Tacho and Charge issue.

Post by DazbodS2 » Wed May 16, 2018 8:24 pm

Hi Ralph, Nigel, James and Bill

Many thanks for your responses and suggestions. Looks like, I’ve got some investigating to do, will report back my findings.

Thanks again.

Darren
Darren - 1970 S2 FHC Signal Red.

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ralphr1780
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#7 Re: Tacho and Charge issue.

Post by ralphr1780 » Wed May 16, 2018 8:41 pm

Warren, I meant the alternator relay which is located next to the battery on the left, not the 3aw of the ignition light sorry.
This is typical of S2. When this relay fails the alternator is no more excited, hence no more charging.
I had exactly the same some time ago.
Good luck and please do let us know your findings.
Ralph
'69 OTS + '62 OTS - Belgium

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DazbodS2
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#8 Re: Tacho and Charge issue.

Post by DazbodS2 » Wed May 23, 2018 7:46 pm

Hi Guys

Problem solved. On further investigation the horn had also stopped working. Neither fuse 6 or 7 had blown but cleaning up and re tensioning the carriers resolved the problem. Unfortunately, I don’t know which one was at fault. Incidentally, I purchased the Series 2 wiring diagrams from CAC Ltd and found the segregated circuits and diagrammatic format very helpful and easy to follow.

Thanks again for all your help.
Darren - 1970 S2 FHC Signal Red.

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