Joined: Aug 2017 Posts: 56 Threads: 24
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Dear Friends,
Can anyone help me to diagnose a problem with my ammeter on a 1937 Opal.
When I apply the brakes, the ammeter jumps to maximum discharge. When I release the brakes (brake lights go off) then the ammeter still registers a full discharge. However, if I gently tap the ammeter with my finger then it returns to the normal vertical position.
Under normal driving conditions, the ammeter registers a small charge as expected.
Many thanks for your feedback.
Matt
Joined: Aug 2017 Posts: 294 Threads: 11
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22-04-2018, 11:21 AM
(This post was last modified: 22-04-2018, 11:23 AM by Ray White.)
They say you learn something new every day. I have never experienced this personally, but my first thoughts were you might have a short in the wiring or switch but then you say the brake lights work O.K. so I am also keen to learn what is causing this. I shall also watch this space. I don't think the ammeter sticking is anything to worry about. What size bulbs are you using?
Joined: Apr 2018 Posts: 507 Threads: 129
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Location: Staffordshire
Car type: Ruby mk 2
I agree the first place to check is the braking light switch.
I am new to A7 owners but the light switch on my Ruby is metal cased which looks like
it could easily short.
Regards
Tim
Joined: Dec 2017 Posts: 1,160 Threads: 68
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Location: Nottinghamshire. Robin Hood County
Car type: Austin Ruby Mk1 1935
Matt, Do you think it could be as simple as when braking the engine goes to idle and therefor no change from the Dynamo. The brake lights come on and depending on what bulbs you are using you correctly show a big discharge on the amp meter when you stop braking and all returns to normal apart from the meter giving a false reading, when you tap it. It either releases the sticking needle or makes possible bad connections at the terminals good again.
John Mason
Would you believe it "Her who must be obeyed" refers to my Ruby as the toy.
Joined: Mar 2018 Posts: 694 Threads: 33
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Location: Lot region FRANCE
I don't think there is a problem with dynamo or wiring etc, its a sticky ammeter needle. I wrote up how to dismantle and repair ammeters for the PWA7C.CO.UK round about march 2017. Let me know if you would like me to send you a PDF by E-mail.
BobH
Joined: Aug 2017 Posts: 926 Threads: 74
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Location: Essex
I would Bob. Cyt660@hotmail.co.uk
Mine often sticks, but a gentle tap (percussive maintenance) ususlly restores normal service... It'll go on the long list of jobs to do!
Regards
Nick
Joined: Apr 2018 Posts: 507 Threads: 129
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Location: Staffordshire
Car type: Ruby mk 2
I would doubt it is just normal discharge.
Not sure what the ammeter max. is but possibly need a discharge in excess of 30 amps
to swing the needle all the way.
This equates to 180w of bulb power.
Just a thought
Joined: Aug 2017 Posts: 294 Threads: 11
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22-04-2018, 08:37 PM
(This post was last modified: 22-04-2018, 08:38 PM by Ray White.)
I was thinking along similar lines. My ammeter shows a max discharge figure of 16 amps so on that basis the wattage of each 6v bulb would be at least 48. This is far more than necessary I would have thought. (If the car had been converted to 12 volts then the figure would be half that.)
