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MG MGF Technical - hand brake light not coming on with ignition


The hand brake light on my mgf 2003 is not coming on and then off when i start the engine. It is meant to come on for a few seconds when the engine starts.
Unfortunately it has failed the mot for this.
When the hand brake is applied it comes on and turns off when released. It also works if the brake hydraulic fluid is low.
Can anyone advise me of what it may be?

Many thanks

warren morrison


The MOT tester is wrong, this circuit for the handbrake light is very simple, 12V is applied to one side of the bulb and earthed via the handbrake switch or the low fluid switch, there’s no facility or circuitry to test the lamp as the tester is suggesting.

I've checked the diagrams in RAVE (Rovers Technical Data) and how my MGF operates.

Your car being a 2003 must be a late registered model as MG started producing TF's in 2002

R.A Davis

Hi Bob,

Thank you for your reply.
Yes you are correct. After paying a mechanic for a few hours with no results I phoned someone who was selling one and theirs was the same. That was a lot of time and expense for the mot guys fault.
You are also correct that mine is a T series.

Thanks again for your help

warren morrison


An MGF and mgtf aren't the same car, they share a lot of common parts and early TF's have a virtually identical wiring system to late model F
R.A Davis

If the light didn't come on at all, the tester was correct in failing it because otherwise you have no warning of fluid loss. Even when the handbrake is off, the light should show when the ignition is switched on and go off when the engine is started. When the engine is running, the light should show when the handbrake is applied.
Have you now got an MOT?
Bernie Higginson


“Even when the handbrake is off, the light should show when the ignition is switched on and go off when the engine is started.”

Which vehicle are you seeing this behaviour on? I've tried it on a late model F and it doesn't do this. I've checked the wiring diagrams for the F and early model TF (pre MY 2005) which covers the vehicle Warren has and neither of these does this, neither of these vehicles has the circuitry to do this.

If you look at the (badly) scanned diagram, you can see the handbrake warning light at the top of the diagram. 12V is applied to the left side of the bulb and it’s earthed via the handbrake switch or the low fluid switch.

I don’t have any diagrams for late model (Pektron) TF’s or Chinese TF’s so I can’t comment on these but as Warren’s is an early TF the warning light is only activated by the 2 switches and doesn't have any facility to test the bulb prior to startup.


R.A Davis

Rob and Warren. Firstly, apologies for my misleading post. I (and the tester) wrongly assumed that there must be a way of testing the circuit, particularly the low fluid one, prior to starting the engine. This has been the case on previous cars I have owned. But I just went out and checked my MGZR and it is the same as the F. ie the light only shows when the handbrake is applied. I do find this a bit strange.
It's quite obvious from Rob's diagram that the only way to test anything is via the light showing or not, which means that if it doesn't show it could be the bulb, or either of the two switches, or the circuit. It also looks like the low fluid side could go open circuit and you could still get a light via the handbrake side. I could be wrong on that, as there is a part in the middle of the circuit in a box that I couldn't quite read.

I only came on this board because I really fancy an F and I'm trying to glean as much information as possible. (I have a '65 Sprite).
Apologies again for the confusion.
Bernie Higginson


No apologies necessary. If you
R.A Davis

This thread was discussed between 08/11/2016 and 15/11/2016

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