Amp draw when driving
 

I have a 6 volt alternator on my car. Yesterday when driving home I noticed about a 6 amp draw on the amp meter. Turning on the headlights did not change the reading. When key is off there is no draw on the meter. Battery going?

Re: Amp draw when driving
 

Have you checked the voltage on the battery with car off and with car running at high idle? It will tell you a lot. You're going to get a ton of "shotgun" answers that will be pretty well worth what you're paying for them. Get back with data, answers then will be more valuable.

Re: Amp draw when driving
 

The battery was at 6.9 volts with car off, low ans high idle. I think I verified the problem, for kicks I turned the disconnect on and the draw went away. I think this verifies the battery issue. Am I correct?

Re: Amp draw when driving
 

Well, I'll give a shotgun answer which should be worth what you're paying for it.

You turned your disconnect 'on' and the draw disappeared ? I may be confused, which is normal, but 'on' means its connected ?

To find the draw, disconnect a battery cable [ in this case ground] and connect a test light/voltmeter between the terminal and cable end. Disconnect in on position. Keep disconnecting things until draw disappears, thats the problem.

Re: Amp draw when driving
 

Bad terminology on my part. I turned the disconnect so the battery was disconnected from the electrical system the amp meter went back to zero. Turned "on" the disconnect and the draw came back. I drove over 50 miles today and it never went to zero as it has done in the past. Also with the ignition on with the car not running there is no draw which seems strange to try and trouble shoot. Seems like a draw would be a draw car running or not with the key on

Re: Amp draw when driving
 

If you're not going to try and find the draw by disconnecting a battery terminal then unhook the alternator.

Re: Amp draw when driving
 

Heres where my confusion is, with the key on and the car is not running there is no draw. I am not sure how to troubleshoot it. My common sense says if there is a draw on the battery it would occur when the car is running or not as long as the key is on. My common sense has bit me before though.

Re: Amp draw when driving
 

Is the Ammeter connected correctly? What does it show with the engine off and the lights on?

Re: Amp draw when driving
 

It reads zero with the car off, goes to about -4 amps if I turn on the lights. This is normal for it and back to zero when they are off. It's been fine for 3 years, just started this yesterday. I normally start it, give it some gas and alternator kicks in reads high for a few and goes to zero when I'm driving. When driving now is reads about 6 amps, when I turn on the lights it does not go any higher.

Re: Amp draw when driving
 

Re: Amp draw when driving
 

Yes you are correct, I thought maybe when I turned on the lights while driving the amp meter might change, it does not. It stays at a steady 6 amps

Re: Amp draw when driving
 

I apologize, my description is all wrong. Alternator is constantly CHARGING at 6 amps there is no draw when driving. Before yesterday the amp meter would go back to zero after a few minutes of driving. .Amp meter at zero when the car is off.

Re: Amp draw when driving
 

I just went thru the same issue. My car also has a 6 v alternator but my ammeter reading was 10-12 amps. Trouble was the battery was bad. Probably a short inside. Replaced it with the new battery from my model T. problem gone.

Re: Amp draw when driving
 

Hmm, well, a hydrometer and a load test should show the state of the battery. But, a new one isn't too expensive.

Re: Amp draw when driving
 

My thoughts as well. I will pull it and have it tested, I had issues with it over the winterso probably time for a new one.

Re: Amp draw when driving
 

The battery voltage at high idle is at 6.9V with 6 amps of charging current? That seems OK, maybe a touch low but 6 amps of charge isn't excessive. If it doesn't level out after a few minutes or the battery voltage doesn't rise to above 7v, then you may have a low cell in the battery. However, 6 amps is not going to kill an alternator, its putting out around 40watts. If the starter turns over strongly, I'd leave it. another thing to check, does the battery have removable caps? if so check the water, then put a charger on the battery overnight and see if it comes up some. I didn't mean to come across as pessimistic or #%$ on my 1st post, just wanted more info. thx

Re: Amp draw when driving
 

From what I've found in multiple sources of information, the GM/Delco 10SI alternators that are modified to output for 6-volt systems generally are regulated internally at 7.5 to 7.8-volts. I feel that this is on the high side for a 6-volt system that would normally run 7.1 to 7.2-volts but that's the way the regulators are made and there is no adjustment for voltage output. They are capable of 63 amp output but that's on a standard unmodified 10SI for 12-volt systems. I'm not sure what the max amperage output of the 6-volt modified alternators is but some claim a regulated output of 50-amps and others claim 60 amps. This is enough amperage to really fry something if it shorts out and that includes a battery.

Normally these type alternators self excite to come on line but it's all controlled in the voltage regulator module. If the module goes bad it won't self excite anymore.

An amp meter indicates flow of electrical power. If it's flowing from the generator/alternator, it will indicate on the positive charge side of the center line. If the alternator is not functioning, and there is any load on the battery it will indicate on the negative discharge side of the center line which is battery discharge. There will always likely be a charge indicated as long as the engine is running since the alternator always compensates for current draw. I agree that 6-amps indicated charge is likely higher than normal. Normal would likely be around 2-amps or maybe a bit more.

I always check the connections at battery first to make sure there is ample power flow available followed by a check at the starter switch, alternator, and terminal block. The alternator should be connected to the terminal box the same at with a generator to correctly indicate flow. The battery is connected to the other terminal in the box which is connected to the other side of the amp meter. This is the only way to measure the flow difference between the battery and the alternator.

Technically, the lights and horn should have been connected to the buss since they are electrical loads but Ford didn't start doing this until around 1940 when they started using a dash mounted headlamp & lighting switch. I think the early engineers felt that the two highest loads should be attached directly to the generator to keep the resistance in the line as low as possible for peak power usage for high draw loads. A 6-volt system needed all the help it could get at the time and especially when it came with a generator that had a max capacity of only around 12 to 15 amps.