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Ammeter reading


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Went for a drive this afternoon and found the ammeter was showing a higher rate of charge to normal.  After starting the engine I would normally see a reading at about half way on the plus side which would then drop to just positive of centre after a few miles. Everything else seemed to be OK.  Tried switching on the lights, slight movement of the needle then back to same position. With the engine off the needle moves normally when switching on the ignition or lights.

Alternator felt hot but not sure if normal, not something I check. Unit is about 10 years old. 

Roger

 

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Sounds like the battery may be failing Roger or perhaps the car has been laid up for a long time and the battery has become discharged? (but that should have gone back to normal after ten minutes or so). The alternator is hot because it is probably working harder than normal. Have  you a meter to measure the battery voltage with? 

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Everything was normal when I used the car 2 weeks ago, battery had been on a maintenance charger over the winter. Engine had started fairly quickly yesterday so no great drain on the battery and covered about 20 miles. Checked the battery voltage this morning, 12.7 volts which would seem to be normal. Started and stopped the engine to recheck voltage, no drop in the reading. Restarted the engine to measure the output form the alternator, got a reading of 13.9 volts.

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13.9 V  is the correct voltage from the alternator so that is working OK.  Does the battery voltage rise to 13.9 with the engine running so it is 'on charge''?

edit - have you made any wiring changes recently like fitting a direct feed for the petrol pump?

 

Edited by RobH
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Interesting point, I added a direct power feed to the fuel pump, with relay, and the ammeter reading is weird now.  I did this after the standard inertia switch just about burned out with the current going through it for the new BOSCH fuel pump that previous owner had fitted.  Also fitted new thicker cable to the pump as well.  Haven’t figured out yet how to get the ammeter to read correctly yet, did consider changing it for a voltmeter.

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4 minutes ago, Scotland Director said:

Interesting point, I added a direct power feed to the fuel pump, with relay, and the ammeter reading is weird now.  I did this after the standard inertia switch just about burned out with the current going through it for the new BOSCH fuel pump that previous owner had fitted.  Also fitted new thicker cable to the pump as well.  Haven’t figured out yet how to get the ammeter to read correctly yet, did consider changing it for a voltmeter.

You'll  need to decide you want to measure alternator output or net current flow into/out of  the battery. When I wired mine  I took the Bosch direct feed out of the  flow through the ammeter  as I wanted to minimize current flows in the dashboard. My ammeter measures the net current flow into the battery only.

I believe that Triumph fitted voltmeters to the later models  because routing the steadily increasing alternator outputs through  a  dash mounted ammeter was an idea whose time had passed.

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The ammeter is really only there to show current flow into/out of the battery. All other loads should be connected to the alternator side of the ammeter. If loads are connected direct to the battery side, they register on the ammeter as a charge when the alternator is running and do not register at all when the engine is off even though there may be a current being drawn from the battery. 

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In that case the ammeter must always have shown the the petrol-pump current as a charge, which would be your "just positive of centre" indication.  

The current must be going somewhere so that leaves three possibilities - either the petrol pump is suddenly taking a lot more current or the battery is not charging properly or there is something else connected direct to the battery which is pulling current.  Cooling fan perhaps?

 

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On 7/7/2020 at 11:18 AM, RobH said:

13.9 V  is the correct voltage from the alternator so that is working OK.  Does the battery voltage rise to 13.9 with the engine running so it is 'on charge''?

edit - have you made any wiring changes recently like fitting a direct feed for the petrol pump?

 

13v9 is not enough to charge a battery correctly. I would want to see greater than 14.3 volt at a couple of thousand RPM.
13v9 at idle would indicate a working alternator though.

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9 hours ago, SpitFireSIX said:

13v9 is not enough to charge a battery correctly. I would want to see greater than 14.3 volt at a couple of thousand RPM.

The Lucas specification for ACR alternators states 13.6 to 14.4 volts at less than 10 Amp charging rate at 3000 rpm. 13.9v  is well within that range so is within specification.  

In any case, the OP is complaining about excess charging, not a lack of it.

Edited by RobH
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I may have solved the problem.

Having done nothing to the car wiring before the increase in the charging I checked the battery connections, clean and tight. Pulled the alternator plug, quite discoloured so cleaned inside of each connector with a swiss file, reconnected to the alternator. Started the engine, after about a minute of running, watched the ammeter drop to a more normal position. Reading 14.2 volts at about 900 rev, I guess a poor connection was affecting the regulator in the alternator. Will go for a run when the weather improves, perhaps being idle for months not helping.

thanks everyone 

 

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