Grahamgl Posted October 19, 2015 Report Share Posted October 19, 2015 Good afternoon, Can I please seek advice from electrical experts? I have changed from a Dynamo to a 45amp Alternator. I already had installed relays to power the dipped and main beams, the feed for the relays was taken from the solenoid, the same terminal that feeds the battery and, according to the wiring diagram, is the terminal to which the Brown wire from the ammeter is attached. Without the engine running, when I turn on the car’s sidelights the ammeter needle shows a small discharge and, when the indicators are also switched, on the needle deflects farther into the negative and back in time with the flasher rate. However, when I turn on the headlights and/or other additional loads, the ammeter needle does not show any additional deflection. I assume this is because they are not wired through the ignition. When the car is running my supplementary voltmeter shows a 14 volt reading. As I switch on various electrical systems, side lights + dipped headlights and the heater fan the ammeter shows an increasing deflection into the positive side of the scale. To me this is saying that the Alternator is increasing its amperage output to the battery to cover the increasing electrical loads of the systems being used. Before I went out on my last run, using a multimeter, the battery showed a charge of 16.3 volts, after a fifty mile run, when I arrived home using the multimeter the battery showed a charge of 17.4 volts. I have not changed any wiring directly attached to the ammeter; the voltmeter has been connected in accordance with an article by IanC on installing an Alternator. My questions are: 1. Have I wired the feeds to the headlight relays correctly or should they take their feed from a different point? 2. Why does the ammeter show an increasing deflection into the positive side with an increase in electrical loads? 3. If my assumption concerning the non increase in the negative deflection when the headlight are switched on is correct, why does the ammeter show an increasing positive deflection when the said systems are switched on when the engine is running? All advice gratefully received. Thanks Graham Quote Link to post Share on other sites
Lebro Posted October 19, 2015 Report Share Posted October 19, 2015 Answer is -you have wired the feed for headlamps to the wrong place for the ammeter to work sensibly. You symptoms make complete sense. To correct, wire the feed to headlamp relays to the load side of the ammeter. Basicaly, the only two things the battery +ve should be connected to are the ammeter, and the starter motor (via the solenoid) This way the ammeter can show exactly what is going in, or out of the battery. (except when cranking the engine) Bob. Quote Link to post Share on other sites
RobH Posted October 19, 2015 Report Share Posted October 19, 2015 Graham - you probably have the headlights and the other loads connected direct to the battery when they should be the other side of the ammeter. The ammeter is reading positive because the current for those loads is flowing through it from the alternator the same as charging current for the battery. I dont know where those voltages came from - that is impossible if you are reading direct on the battery and it is good. Sounds like your multimeter may be up the swanny . Quote Link to post Share on other sites
Grahamgl Posted October 19, 2015 Author Report Share Posted October 19, 2015 Bob/Rob, Thanks for the quick replies. In view of Rob's comment about my Multimeter I went out and bought another. This one reads 13.2 volts across the battery, so I guess the other meter, Maplin's finest must be duff and I didn't keep the receipt!. If I understand you both correctly the feeds to the headlight relays must come off the feed to the ammeter. According to the wiring diagram the feed side of the ammeter comes from the regulator box via a Brown/White cable. I have used the regulator box (internals gutted) as the junction box to join all the wires together. So, if I am correct, all I have to do is use the small unused blade terminal on the regulator to feed the relays. Am I correct please? Thanks Graham Quote Link to post Share on other sites
RobH Posted October 19, 2015 Report Share Posted October 19, 2015 Yes that sounds right Graham. Its not a problem electrically and everything will work OK as it is wired, it just that you need to re-arrange things if you want to make the ammeter read correctly. Quote Link to post Share on other sites
Grahamgl Posted October 19, 2015 Author Report Share Posted October 19, 2015 Rob, Thanks for the quick response. I would like to see the ammeter showing a true picture. It should not be a major task to change the wiring, remove the ring terminals, replace with soldered on Lucar connectors and use a piggy back terminal (I have two relay feeds off the solenoid). Thanks again. Graham Quote Link to post Share on other sites
stillp Posted October 19, 2015 Report Share Posted October 19, 2015 Maplin are usually pretty good about changing stuff without a receipt. Pete Quote Link to post Share on other sites
Lebro Posted October 19, 2015 Report Share Posted October 19, 2015 I may be worth checking the battery inside your multimeter. An almost flat battery can make a multimeter do funny things. Bob. Quote Link to post Share on other sites
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