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MG Car Repair/1961 MGA Generator


Hello to the Experts and thanks in advance !!!!

Currently experiencing the following issues and am not sure if it is the generator or the regulator.
- Ignition light stays on while car is running
- Battery must be boosted to start the car
- Recently while driving, the engine started to stumble and then the car stalled.
- Generator was removed thinking it was likely the brushes.... however brushes were just fine but connector wires were loose. All tightened up and replaced brushes as anyway as I had new ones
- Inside of generator had minor flaking but certainly did not look copper clean.
- Checked belt and fan and all fine... generator re-installed.\
- All this and absolutely NO difference... same light on .. stumbling ... and draining battery.
??? Replace Generator completely
??? Could a faulty regulator ( control Box ) cause the same prob.

Hi Steve
Sounds like either a faulty dynamo or a faulty voltage regulator.

You can test the dynamo as follows:

1.   Disconnect D and F wires (thick and thin) from dynamo.
2.   Connect D and F terminals (on dynamo) together with a piece of wire.
3.   Connect voltmeter between this wire and Earth.
4.   Run the engine at 1,000 rpm (do not race the engine).
5.   12-13V   = normal.
6.   5-7V   = faulty armature.
7.   1-2V   = faulty field coils
8.   Remove the jumper wire from D and F.
9.   Attach an ohm meter between F and body of dynamo.
10.   Resistance should be about 6 ohms.

If the dynamo checks out OK then you probably have a faulty voltage regulator.
Let me know what you find.  

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Barrie Jones


MG Sports Cars from 1949 to 1980 - Including MGB, MGBGT V8, TF1500, TF, TD and modern Midgets. I also specialise in SU carburettors, Lucas wiring, suspension, steering & brakes.


I have owned my 1955 TF1500 since 1966. Technical specialist for the TD and TF with the MG Car Club T Register. Also owned 20 MGBs and currently own an MGBGT V8. Written 3 books on MGs and produced a DVD on how to strip and rebuild the TD/TF gearbox.

MG Car Club.

Barrie's Notes on the 1953-55 MG TF (author). /=====/ Barrie's Notes on the MGB (author). /=====/ Barrie's Notes on the MGB GT V8 (author). /=====/ The Essential Buyer's Guide to the MG TD, TF and TF1500. (author)

M Phil, C Eng, BSc (Eng).

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