samneric Posted January 18, 2008 Author Share Posted January 18, 2008 There are dash mounted ampmeters that have the shuntbuilt into them. These were in vogue back in the sixties, many Britsh cars had them (good old PoD -> Prince of Darkness) Problem is the large gage wires needed to be run to and fro the meters. The model Cougar mentions is a better choice for your application. Small gage wires (18 or 20 AWG) can be run to the dash mounted meter. Only the newest style Amprobes measure DC the older units only measured AC. http://en.wikipedia.org/wiki/Clamp_meter Hey thanks Nipper, Skip, Cougar !!... Sorry for the delay in replying.... I'll see if I can track down one of these ammeters or at least check the voltage output under load... Oh one other question: Can I connect this ammeter in series with the alternator output to the battery or other points along the charging line if disconnected? I'll post back when I have a result. Steve Link to comment Share on other sites More sharing options...
Skip Posted January 18, 2008 Share Posted January 18, 2008 Hi Steve, you are most welcome, Cougar one of our best electrical trouble shooters needs a shout out also. You can connect in series any amp meter capable of reading at least 50 amps to the alt output wire. Be aware this will only show the charge amperage. It is better to wire the ammeter in series with the smaller wire that connects the positive battery post to the fusible links. In this fashion it will show the charge state of the battery. This is the important current. For instance If the car is not running but ig sw is "on" and the headlights are switched on. The meter will show deflection in the negative direction showing the amperage being drawn from the battery Also known as dis-charge. If the car is started, the alt will (should) show the meter swing the other direction (positive) meaning the battery is being charged. If a situation should present itself where the car is running (above 1500 RPM) and the meter swings negative - something is a miss in the charging system. At idle it is not uncommon to see some battery discharge (meter showing a negative amperage) if many electrical devises are in operation, it should go positive as soon as the engine RPM is increased. After the alt brings the battery back to a charged state after starting, it should show a slight positive reading. If you wired the meter as you asked (series with the alt output wire) you would not see the negative readings. Sorry for the lengthy diatribe, I got a little carried away Hope this helps. Link to comment Share on other sites More sharing options...
Cougar Posted January 19, 2008 Share Posted January 19, 2008 Instead of installing a ammeter I think you should consider a using a voltmeter instead. While knowing the charging current value is nice I think knowing what the voltage at the battery is a little better. The installation is a little easier also. While connecting directly to the battery is good, it doesn't have to be right at the battery and could be tied to the fuse panel in the dash. By monitoring the battery voltage and making sure the value stays between 12.5 and 14.8 volts you will know your battery is getting the charge it should be. Link to comment Share on other sites More sharing options...
samneric Posted February 11, 2008 Author Share Posted February 11, 2008 Instead of installing a ammeter I think you should consider a using a voltmeter instead. While knowing the charging current value is nice I think knowing what the voltage at the battery is a little better. The installation is a little easier also. While connecting directly to the battery is good, it doesn't have to be right at the battery and could be tied to the fuse panel in the dash. By monitoring the battery voltage and making sure the value stays between 12.5 and 14.8 volts you will know your battery is getting the charge it should be. Tas been a while since dabbling with my charging system and I decided to have another stab at this after buying a new battery to rule that out as well. So I now have a new Alt, new Batt and new battery connectors on the end of the wires. I measured voltage with the car off and it read 12v. I ran the car and I get 14-15 at various probe points on the system.... My latest acquisition is a clamp ammeter so today I read the amps at various points along the line. From battery neg to engine block is about 6a. From Fusible Links back to battery pos is about 4a. Out from the alternator was -4 (maybe the sign changes depending on the direction of the current flow). Engine revs made no difference to the amperage. I looked at the wiring diagram to get a little insight. It looks as though the charging cable goes to the fusible links, then on the plug that connects to the alt, one wire goes to the dash to indicate charge and the other seems to junction with the charge line. There is a crack in the casing of one of the plug wires but other than that all seems ok. Shouldn't I get an increase in amps out and into the batt when the engine is revved??? Can I connect the alt output directly to the batt pos to test the alt??? This has me flumuxed. I need to know where to start trouble shooting with my new wonder ammeter. Thanks all, Steve Link to comment Share on other sites More sharing options...
nipper Posted February 11, 2008 Share Posted February 11, 2008 You need a load. Turn everything on and rev the engine at 2500 rpms and see what you get. You can rev the engine all you want, but with no demand on the system, there will be no current draw. Doesnt take much to run an engine. nipper Link to comment Share on other sites More sharing options...
Durania Posted February 11, 2008 Share Posted February 11, 2008 You need a load. Turn everything on and rev the engine at 2500 rpms and see what you get. You can rev the engine all you want, but with no demand on the system, there will be no current draw. Doesnt take much to run an engine. nipper +1 Go out there and turn the inside fan all the way up, headlights on bright, and windshield wipers on. That will give you plenty of load on the system to do an adequate check. It sounds like you got it worked out though. Link to comment Share on other sites More sharing options...
Cougar Posted February 12, 2008 Share Posted February 12, 2008 Can I connect the alt output directly to the batt pos to test the alt??? This has me flumuxed. I need to know where to start trouble shooting with my new wonder ammeter. Thanks all, Steve You do not want to connect the alternator output directly to the battery. Basically it already is, except for a fuse for protection which will be bypassed if you do that. The clamp on meter will change polarity depending which side of the clamp is towards the power source and the polarity of the source (usually positive for autos). Unless you are looking for a power drain I'm not sure what you are trying to do for a test. If you are looking for a drain then you need to shut everything off and follow the current leak. It sounds like there isn't much drain if there is some and you may need to use a different. in line check, if that is the case. Link to comment Share on other sites More sharing options...
samneric Posted February 12, 2008 Author Share Posted February 12, 2008 You do not want to connect the alternator output directly to the battery. Basically it already is, except for a fuse for protection which will be bypassed if you do that. The clamp on meter will change polarity depending which side of the clamp is towards the power source and the polarity of the source (usually positive for autos). Unless you are looking for a power drain I'm not sure what you are trying to do for a test. If you are looking for a drain then you need to shut everything off and follow the current leak. It sounds like there isn't much drain if there is some and you may need to use a different. in line check, if that is the case. OK, Thanks for the info, I tried swapping the direction of the clamp and it did switch the polarity... New readings: Engine on, Everything off: 5a out of the batt, 2-3 in. Engine on, Everything on: 33a out of the batt, 2-3 in. There are 15a going into fusible link#2 via the large diameter white wire. Still only 2-3a coming out of the fuses and going into the battery. Is this the correct amperage for a slow charge or chould 15a be comming out and into the battery? Steve Link to comment Share on other sites More sharing options...
Cougar Posted February 12, 2008 Share Posted February 12, 2008 I assume the white wire you are talking about is going to the alternator output connection. I am still unsure what you are trying to find out by doing these tests. If you are trying to see if the alternator is charging the battery properly then you need to check the alternator output lead current and compare that to the battery lead current that runs to the accessories. You also need to run the engine up to around 2,000 RPM while testing so the alternator will be able to generate proper charging current. For this kind of test it is easier to just measure the voltage at the battery to see if the charging system is working as it should be rather than looking at current. If the alternator is working as it supposed to the voltage at the battery should be between 12.8 and 14.8 volts, with or without a load on the system. If you are looking for a current drain on the battery while the car is parked you need to check for current drain with everything off, like the car would be when it is parked. There still is going to be a small drain for some things and this current should be less than 80 milliamps coming from the battery. Typically, it is around 25 milliamps. Link to comment Share on other sites More sharing options...
Skip Posted February 12, 2008 Share Posted February 12, 2008 Hi Steve, since it really looks like you are doing you homework. Cougar's words are pointing you in the correct direction. I have a problem with some of your results Engine on, Everything off: 5a out of the batt, 2-3 in. I don't know what the "2-3 in" means?Do you mean 5a out of the alternator? 2-3 into the battery? Engine on, Everything on: 33a out of the batt, 2-3 in. see my above statement There are 15a going into fusible link#2 via the large diameter white wire. Still only 2-3a coming out of the fuses and going into the battery. This is what I was thinking you were saying. Is this the correct amperage for a slow charge or chould 15a be comming out and into the battery? Yes, the charge going to the battery will be large ( black lines showing varring amount of current vs width) just after starting - to recharge the battery. After that the normal operation will maintain the charge and the alt output will run the car Hope this "visual" helps. Link to comment Share on other sites More sharing options...
samneric Posted February 14, 2008 Author Share Posted February 14, 2008 Hi Steve, since it really looks like you aredoing you homework. Cougar's words are pointing you in the correct direction. I have a problem with some of your results I don't know what the "2-3 in" means? Do you mean 5a out of the alternator? 2-3 into the battery? see my above statement This is what I was thinking you were saying. Yes, the charge going to the battery will be large ( black lines showing varring amount of current vs width) just after starting - to recharge the battery. After that the normal operation will maintain the charge and the alt output will run the car Hope this "visual" helps. I like the Diagram, thanks! Yes, you got what I was trying to say.... I appologise for the confusion, I like to understand things from a "way things work level" so in reference to in and out I was talking about electron (current) flow as marked in green here: Hanyways, Following an incident where I got stranded out and about, I took some tools and charged battery out to my car the next day. The lights on the dash and all other components lost power and came on sporadically esp one time I moved the battery around. I tightened the bolts securing the battery-to-starter motor cable to the terminal clamp and at least got everything back on again. Still no luck starting but I figured I had a bad connection on the new starter cable terminal clamps so I planned on buying a new starter cable and engine to battery cable so make sure there was enough current getting to the starter. I started pushing the car to a place where I could leave it until I could get it towed and luckily some passers-by helped me to bump start it. I got it home and decided to first try swapping the heavy duty gauge wires from my spare suby onto the DD. It will turn over with plenty of power now although I think all the twisting of the ignition key has worn something out because I have to turn the key all the way and then release it slightly to get the starter cranking... Might try swapping in the starter solenoid from my spare Brat to rule out mal-function in the high-current side of that relay. Thanks for help y'all! Steve Link to comment Share on other sites More sharing options...
samneric Posted February 16, 2008 Author Share Posted February 16, 2008 Switched starter/solenoid over from spare Brat... Cranked right up - no more clickety click !!!!!!!!!!!! :banana: Glad to put this thread to bed Now, new solenoid..... $444 from Napa Steve Link to comment Share on other sites More sharing options...
Cougar Posted February 17, 2008 Share Posted February 17, 2008 The problem is most likely just worn solenoid contacts. You can replace them for around 10 dollars doing the work yourself. Link to comment Share on other sites More sharing options...
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