Need electrical help (1 Viewer)

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Hi all,

I need some electrical help. I have a 1971 fj40 with the stock engine and stock 40 amp alternator. My problem is I can't run my headlights and heater at the same time without discharging the battery. When I turn on the headlights, my ammeter drops to just above 0. If I turn on the heater with the headlights, it drops quite a ways into the negative on the ammeter. Just the heater alone will also drop the ammeter to just above 0. A normal reading on my ammeter is about halfway up on the positive side without the heater or headlights on.

Things I have done:
1. Had alternator tested at auto parts store - good
2. Checked connections and cleaned any that looked questionable, including the fuse box.
3. Checked all the grounds that I can find - I even replaced the ground wire from the starter to the frame and both battery cables.
4. Ohmed out all the connections I can find and/or get to, to make sure nothing is shorting or grounding out.
5. Everything works, so I started disconnecting things (lights, horn, taillights, etc) one at a time looking for a possible short.
6. Checked voltage with a meter at all lights and connections. All were basically at 13 volts. All lights, gauges and accessories seem to be working fine.

So far, nothing I have done has worked. I realize that I only have a 40 amp alternator, but nothing has been added to this rig to require more amps (i.e. no winch, stereo, etc). It is still stock. Therefore, the stock alternator should work fine. Right? I could always put in a higher amperage alternator, but it seems that would only mask the problem (or not fix it at all). I'm assuming (I know, I know) that this is a grounding issue. I've checked the grounds that I can think of (battery, starter, taillights, marker lights).

What else should I do? Are there other grounds that are somewhat hidden? Any obvious spots to look? Right now I'm open to suggestions. I have spent probably 20 hours looking for this problem, and I'm about to the point of taking it in to someone to track down for me. I just hate having to pay someone else for something I can do myself. Please help.

Thanks,
Kyle
 
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# 1.. is the battery up to snuff? a healthy battery is needed to maintain a good relation w/ the alternator.. bench testing on a alternator w/ external voltage regulator is only 1/2 of a test.... the regulator may kick-out under a load...
 
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Sounds like you have covered a lot. When I had a similar problem, it was with the small connection blocks on the bib. The ones that hold the ground for the head lights and the connections for them.
Mine were rusted pretty bad. So I cut them out, and grounded the lights to fresh metal. Worked very well,

When your lights are on are the dim, or not?
 
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Another thing to look at. If the diode trio in the alt has one bad diode out of the pack it will still put out but only a limited amount. Testing on the vehicle will not always show a problem. It will show that it is charging,but will not always show that it is not putting out enough volts to handle your load. Been through this before with a different vehicle and ended up pulling the alt out and taking it to the local alt guru to find the problem.
Good luck finding your problem.
 

73lndcrsr

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Let me ask a question or three.

1. Does the battery take a good charge?
2. What is the voltage between the battery terminals with no load?
3. Does it drop when you add the load?

It almost sounds to me that your battery has a bad cell.

I would also see if you can get an actual current reading during load with an inline meter or a clamp on meter.
 

Coolerman

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According to the FSM the stock alternator does not put out any current until the RPM's get above 800 RPM +- 150 under no load. With the laod you are talking about the regulator SHOULD tell the alternatpr to start working. Try the same test with the RPM around 1000-1500 RPM and see what you get. If it still is not charging then I would suspect the regulator is defective.
Image2.jpg
 
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My 68 does the same thing but only at idle (600 RPM). While driving at about 1500 RPM everything is fine. You don't say if you lights are dim or not, my are dim at idle and my blower motor speeds up with the RPM. If the amp meter reads that way at idle but charges better when the RPMs are up I wouldn't worry about it. I been driving mine for over thirty years that way. I had more than cruisers act this way, of course this was in older vehicles.

John
 
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Okay, I'm back. Sorry, I had to sleep for a few hours...

# 1.. is the battery up to snuff?

Good question. It is about a year old, but it was not a real high quality batter to begin with, but not cheap either. I will get it tested today.

When I had a similar problem, it was with the small connection blocks on the bib.

I checked these, and they weren't too bad. I cleaned them up, anyway.

When your lights are on are they dim, or not?

They are not really bright (not todays standards, anyway), but they are not dim, either.

If the diode trio in the alt has one bad diode out of the pack it will still put out but only a limited amount.

Will this show when tested at an auto parts store? I did have it tested at Schucks, and they said it was good. If it doesn't show, that would explain a lot.

1. Does the battery take a good charge?

Seems to. As stated above, I'll get it tested today. On a side note, I do not have a problem starting the rig. However, I don't run multiple accessories either.

2. What is the voltage between the battery terminals with no load?

14.5 volts +/- (It is between the 14 and 15 volt lines on my tester)

3. Does it drop when you add the load?

Yes. 13 volts with headlights. Barely over 12 with the headlights and heater. So, does this mean it is the alternator or the battery?

According to the FSM the stock alternator does not put out any current until the RPM's get above 800 RPM

I've been doing my tests at 1800 - 2000 RPMs. Yes, the amps significantly drop at idle, but at 2000, the alternator should be putting out at full.

If the amp meter reads that way at idle but charges better when the RPMs are up I wouldn't worry about it. I been driving mine for over thirty years that way.

Mine does show more charge at 2000 rpms, but it is still on the negative side of the gauge. I'm assuming (I really need to stop using that word) that if I run it in the negative, that will run my battery down fairly quickly. I hit a rain storm the other day, and turned on my lights, heater to defog the windshield, and windshield wipers. My wipers would barely go (alone, they work fairly well). Needless to say, that kind of sucked.

So, as I stated above, the voltage drops between the terminals under load at 2000 rpms. What exactly does this signify? Battery or alternator?

Thanks for all your help so far! I really appreciate it.
 

Coolerman

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Forgot to ask but what kind of headlights are you using? Are they stock sealed beams or replacement H4's or what. If they draw more current than stock that might cause this issue. The only other thing I can think of is a short in the headlight system or an amp gauge that's not quite reading correctly.

Do you have access to a DC clamp on amp meter? Might help to see just where and how much current is being pulled from the heater circuit and headlight circuit.
 
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They are stock headlights. No, I don't have a clamp on ammeter. I did go and get my battery and alternator tested. I just had the alternator tested about a month ago, and it was good, but I thought it would be better safe then sorry. Alternator was still good. Battery was bad. "woohoo!" I think, while still at the auto parts store.

But then I get home and install the new battery (this time not a cheap one), install the alternator, and the same thing is still happening. :censor: This is frustrating. It seems there is a bad connection somewhere. The ammeter is flickering slightly and my tachamoter bounces around a little bit. I've checked everything I could think of. Could a bad coil or distributer be causing these symptoms? That is the only other electrical that I have not gone through. Any other ideas?

Thanks again, everybody.
 
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Momentarily "full field" the alternator (By temporarily connecting the F terminal of the alternator to the B+ lug) with the lights and heater on and see what the current flow and voltage is. If the amp meter reads zero and tghe voltage is 14.5 V or higher, then the alternator and wiring is good and it is probably a bad regulator or regulator circuit.
 
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Sorry to sound stupid, but I need some help with Pin Head's suggestion. My electrical skills are somewhat limited (obviously, since I can't figure this problem out!) How do I connect the B+ lug with the F terminal? Do I use a separate peice of wire? I'm guessing I unhook the plug to reach the F terminal? I know which one it is, I just don't want to short anything out. Where do I check voltage? I guess I just need more of a step by step procedure for this.

Thanks!
 
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Howdy,
Below is a post of mine to the thread "Charging or Not." If none of the previous solutions works, you might want to investigate this avenue.

"I just had a similar problem at 1AM driving through SanAntonio, TX. Everything had been working fine for the past 10 days and 2500 miles then dim lights and discharging Ammeter. My 40 has two alternators (one for a belt tensioner) with my wiring set up to allow me to swap as needed (both are internally regulated). I made the swap but the problem remained. This led me down a different path. Behind the gauge cluster in the wiring harnass is a factory splice. The white/lightblue wire comming off the alternator doesn't go directly to the ammeter. It along with the same color wire on the ammeter and a third wire going to the key switch are crimped together with small brass crimp ring. During my delima, just wiggling the harnass behind the gauge cluster restored charging. It failed again after I got home which led me to this discovery. I replaced the loose splice ring with a small split-bolt and have had no problems since. I hope this helps."

Leon...
 
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Leon - Thanks, I'll check it out.

BC - yes, they did the full test on the alternator twice and both times they said it was in great shape. It is externally regulated, so the regulator was not tested. Looking back through my posts, I noticed that I neglected to say that I replaced the regulator during all this. So, it is a brand new voltage regulator. Needless to say, it did not fix my problem.

Thanks for the ideas.
 
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alternator problems

"Will this show when tested at an auto parts store? I did have it tested at Schucks, and they said it was good. If it doesn't show, that would explain a lot."

I am not a charging system expert, I just know what I experienced. I was having trouble with occasional low voltage problems. When I wasn't using much in the way of electrical items everything was fine, but headlights and other high power items would make the idiot light start glowing (not real bright and obvious, just barely glow) signifying a low voltage situation. Daytime without headlights and other power robbing items and the battery stayed charged. I went to the local auto electrical guru and he checked it and said it was charging. I described what it was doing so he checked further and found a bad diode.
As for the counter people at Schucks, they may or may not know more than how to hook up and check for charging voltage. Obviously, I don't put much faith in their abilities since I don't know their experience. Look for some of the wiring connection problems that the others have suggested to look for. If you don't find a cure you might look for a one man shop that has been in business for a long time and get his assistance in further testing your alt. In my experience a bad diode will not readily show up in the run-of-the-mill testing.

Good luck
 
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How do I connect the B+ lug with the F terminal? Do I use a separate peice of wire? I'm guessing I unhook the plug to reach the F terminal? I know which one it is, I just don't want to short anything out. Where do I check voltage? I guess I just need more of a step by step procedure for this.
!

Just jump the terminals with a piece of wire, paper clip, two screwdrivers or anything else that is metal you can get in there without shorting to the case.

It doesn't matter whether or not you remove the plug for the Field wire. Your choice.

Put your volt meter on any hot wire anywhere (like the battery, or B+ lug of the alternator) since it is all connected. Choose something close to the alternator.
 
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Handcannon - Thanks. I will definitely look into this. What you describe is pretty much exactly what mine is doing.

Pin Head - Thanks. I just needed a little more clarification. I'm at work today, so I'll check this first thing tomorrow and report back.
 

MrMoMo

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A normal reading on my ammeter is about halfway up on the positive side without the heater or headlights on.

That throws a red flag up for me...

This is saying that without ANY loads on (other than ignition) your battery is NORMALLY accepting 15 or so MORE amps of current than it is putting out. That is NOT a good thing. Your ammeter should normally rest at zero. A reading in the positive side shows that your alternator is having to put power into your battery - this to me says that the battery can not provide enough.

What you should be seeing is a slight drop to the negative side initially when you turn a load on, which then goes back to zero after a few seconds. This says that your battery started putting out power, and then your alternator kicked in and started charging it at the same rate it was being depleted.

The only time your ammeter should be on the + side is after starting or running a high load. The alternator needs to replenish the charge that was drawn out for starting, so for a few seconds after starting it will be putting more power into the battery than is being drawn out of the battery (a + reading)

Likely you will also see a negative reading when at idle with the headlights and heater on, and perhaps it bounces with the turn signal. Once you rev the engine up you will see a slight deflection to the positive side, as the alternator is charging the battery.

Being in a constant state of charge can damage your battery, if it is not already damaged.

Check the water level in your battery if it is a serviceable battery, if you are low on water you will not be able to fully charge. Also, remove the leads and cean your battery terminals with a good wire brush.
 
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Mr MoMo - Good point. It is one of those things that has been like that since I got it. I never really thought about it not being a volt meter and not wanting it deflecting to the positive. Once you said that, I was like "duh".

So, why is my ammeter always deflecting to positive when no load is on the battery? Likewise, why is it deflecting to negative when I do put a load on the battery. I'm guessing I have a grounding problem. But, for the life of me, I can't find it.

I do know that it is not the alternator (new one today), battery (new one a couple of days ago), or voltage regulator (new one a few weeks ago).

Any other suggestions besides taking it to someone that knows what they are doing to fix it? This is really driving me nuts.

Thanks everyone for all the help so far.
 

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