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TR7 Alternator replacement


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Hi everyone, Some words of advice required for a hesitant DIY mechanic! Having ordered a new alternator for my 1981/2 TR7 dhc, Rimmers have supplied one that looks dimensionally the same as what is on the car but the plug sockets for the wiring are completely different. Rimmers are sending a plug conversion kit i.e. a plug that fits the socket on the new alternator but there are no instructions on which wires to connect to which connectors in the new socket. Anyone got any advice on this. I attach photos of the old, and still in situ, alternator, and I am mulling over whether to try to swap the cables and sockets over myself or surrender gracefully (chicken!) and book the car in somewhere. Last photo is the new alternator showing the completely different socket for the plug.





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Hmm, not sure which is the original type of alternator. But the new one is a clear copy of the lucas ACR.

I "think" the thick brown cable and the smaller brown with yellow stripe may already go to a plug that will fit your new alternator. 

I am not an expert on TR7 wiring but I am wondering if the current (sorry) alternator has a battery sense wire or suchlike? But on the new one, it should be 1 or 2 thick brown wires to the 2 large terminals, and the thinner brown/yellow to the small terminal, that operates the ignition light.

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When I converted my Herald to an alternator an auto-electrician told me to join the thick brown and brown/yellow cables going to the control box together then take one thick cable with LARGE Lucar connector to one of the large spade connections on the alternator.

The thin yellow/brown cable with the small Lucar connector for the ignition light then went to the small spade connector on the alternator.

So on my Herald there are only two cables going to the alternator. I presume there is a buzz bar within the alternator connecting all the large spades together.

My current Herald and the first one I converted have covered tens of thousands of miles without issue.

Your original connector looks (?) to have one thick and one thin cable going in to it.


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Looking at the wiring diagram the thick brown wire is the power, the thin brown one voltage sensing and the brown/yellow ignition light. It looks like the latter goes to the small terminal in your last photo, the large brown to the middle one and the small wire to the last...

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Big thanks to the advice received which meant that I have successfully swapped the Alternator. Checking the number printed on the old alternator it appears to be one used on a Massey Ferguson tractor (?!?!) but the new one fitted easily enough save for the awkward to reach bolts! Upon removal it was clear that the 3 wires were originally on the one plug as one had just been cut (see photo) but all back together and a few miles round the block seem to confirm it is charging as it should. So once again big thanks to everyone, proving the value of the Forums 😃




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