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MG MGA - STRANGE NOISE LIKE A FAN RUNNING

Just arrived in Torquay at the end of the Great Ocean Road, checked into the motel, then off to dinner... fired the car up and a new STRANGE NOISE came from up front, like a loud fan sound.. immediately switched off the ignition but this noise continued. Switched off the battery isolator switch and the noise stopped.

Switched on the isolator switch and the noise started again, ignition still off, so nothing running in the engine.

It sounds like it is coming from the front near the fan but nothing is running. So, took a taxi for dinner...

Any ideas welcome, as I am reluctant to drive with this noise continuing and we were hoping to get to Macedon tomorrow.

Doug
Doug Wallace

Heater fan?
Art Pearse

Back-feeding the generator? I don't know if this is even possible, but there are only 3 possibilities. Heater, genny, rad fan if equipped.

fuel pump might transmit noise through the fuel line, but it'd be easy to locate that.
MAndrus

Lift the bonnet and have a look is always a goog starting point
A J Dee

Have you turned on the heater fan by mistake?

Reminds me of a guy who turned up here with a midget complaining that all his indicators were flashing after an MOT test - told him to turn of the hazard flashers ....
Chris at Octarine Services

I wonder if a fault in the voltage regulator would actually cause the dynamo to run as a motor, as MAndrus suggested?

When you turn on the ignition, does the charge light come on?

A Taxi for dinner? That's pushing the boat out ;o)


Dave O'Neill 2

so what was it?
Graeme Williams

The dynamo doesn't have enough power to run as a motor if the fan belt is installed. But yes it will run as a motor if there's no resistance - I had it happen once when the dynamo pulley disintegrated and took the fan belt with it.
Dominic Clancy

Thanks for all replies.
Art and Chris, after reading your comments I was convinced it must be the heater fan, which I had in fact turned on whilst driving along the Great Ocean Road.

Early morning I checked and that was not the reason for the noise. It was much louder than the heart fan.

I had a fan which had been fitted of which I had no knowledge: the large ducting from the grille to the air filters had a fan fitted inside with the switch fitted to the F {fog lamp} switch, which has been a spare switch for the past 59 years. I must have inadvertently flicked it on!

Has anyone got this fan on their MGA? It must have been fitted at the time of the major mechanical work by Bob West 2 years ago.
Doug Wallace

There was a discussion a while ago on fitting bilge fans to the LH ducting to the carbs to cool them in hot weather.
Cam Cunningham

They have become fairly common since I installed mine five years ago. It works a treat to prevent (alcohol laden) fuel boiling in the carbs in hot weather during slow driving, idling, or on restart after a short period of stop.
barneymg

Doug

I transferred my bilge fan to the heater ducting. Works well. At a guess it doubles the normal airflow through the heater matrix.

Steve
Steve Gyles

This thread was discussed between 27/04/2017 and 01/05/2017

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