Resolved Battery not charging after sitting for 2 weeks

[sebas-1024]

Hi again, back with more issues on my '92 Galant. I had the car parked for about 2 weeks while I swapped my rusty fuel tank for a not so rusty one, I was about to take it for a drive and noticed that the battery was discharged even though the car had been on for 20-30 min, checked battery voltage with the car on and got something like 12.5 V which means the alternator is not charging the battery.

Had a look at the thick wire that's connected to the alternator by a nut and noticed a pretty considerable level of corrosion, went to take the nut off and the bolt snapped, so that was easy. The other connector which has 2 wires looks Ok enough that I don't think it would be the cause, but I'm not even sure about what those cables do, so I could be mistaken.

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Image 1. This is where the thick wire connects (or used to anyway)

Tried getting the alternator out but it seems to be impossible without getting the steering pump or maybe the radiator out, at that point I decided to stop before I could do any more damage and ask around here.

1. What should I check first? Will be replacing that thick wire terminal since it's out already.
2. Is the bolt for the wire in the alternator replaceable somehow?
3. Any fuses or relays for the alternator? Could jut be a blown fuse and I'm about to take apart the entire car for no real reason.

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Image 2. There was a 40 A fuse where the red line is that seemed to be "working" but had to destroy to get out, seemed to be almost fused with the fusebox, anything to do with the alternator?

4. Any way to take out the alternator without having to disassemble anything that's full of oil or coolant?
5. What are the cables in the alternator for? I found 3 in my case.

Long post as always, sorry and thanks for your help!

 

[steve]

That bundle of wire is what somebody replaced the alternator fuse with. I guess they didn't know that it bolts in so this was their solution.

The B+ output post is part of the voltage regulator so replacing it will fix the post. Look for an Automotive electrical rebuilder in your area and take it to them.

 

[sebas-1024]

That bundle of wire is what somebody replaced the alternator fuse with. I guess they didn't know that it bolts in so this was their solution.

The B+ output post is part of the voltage regulator so replacing it will fix the post. Look for an Automotive electrical rebuilder in your area and take it to them.

Do you happen to know the amps for that particular fuse? Can't seem to find it in the Service Manual.

 

[biglady112]

80-100amps. Anything you can find in that range is fine.

 

[steve]

Yep, on a DSM it's either depending on the alternator output. If you have the Galant's high output alternator use the 100A.

If you have the FSM try looking in the electrical manual for Power Distribution.

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[sebas-1024]

Thanks guys, guess I'll look for a 100 Amp to be safe. Will update if I can fix the alternator problem as well.

 

[We're on Boost]

Thanks guys, guess I'll look for a 100 Amp to be safe. Will update if I can fix the alternator problem as well.

The Bussmann FLM100 (100 amp) that Steve showed is what I bought for a spare, for my 1990.
I found it by looking at fuse listings for 2g Talon or Eclipse turbo models in Rock Auto. The 1g listings showed the 80 amp.
Here's a link to their "more info" page for the FLM100:

More Information for BUSSMANN FLM100

 

[sebas-1024]

Any way I can verify the kind of alternator I have? No idea if it's the high output alternator or not.

 

[TerminalTalon]

Clean the case and find any number on it then search that. Usually on the connector side.

 

[sebas-1024]

Yep, on a DSM it's either depending on the alternator output. If you have the Galant's high output alternator use the 100A.

If you have the FSM try looking in the electrical manual for Power Distribution.

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Hi, still have not gotten around to fixing this but was looking at the diagram and it shows 2 wires (the 5F-W) that go from the 80/100 Amp fuse to the B-terminal in the Alternator. My car only has a single thick wire going to the B post, there a few smaller gauge wires that go to what I believe is the S port of the Alternator, for the voltage regulator, am I crazy or are those 2 wires shown in the diagram too small for the current that the alternator is supposed to be able to output? Maybe that was modified in my car as well, but I still find it odd that it shows small wires.

 

[steve]

The two wires are a pair of 5mm^2 wires each about 11awg. Galant's might have a single 8mm^2 white wire in their place or someone might have replaced them. The bigger the wire between the alternator B+ and the battery the better since 80-100A of current passes through it but the factory also has bean counters that want to save money and don't care if you loose voltage and heat up as long as it doesn't melt and start a fire.

 

[sebas-1024]

The two wires are a pair of 5mm^2 wires each about 11awg. Galant's might have a single 8mm^2 white wire in their place or someone might have replaced them. The bigger the wire between the alternator B+ and the battery the better since 80-100A of current passes through it but the factory also has bean counters that want to save money and don't care if you loose voltage and heat up as long as it doesn't melt and start a fire.

Ok, so if not modified it should be something like 3.2 mm in diameter without insulation for a Galant. Guess I'll check if that's the case or not, but you're right, a bigger wire should be better to avoid heating issues. Thanks!

 

[We're on Boost]

Ok, so if not modified it should be something like 3.2 mm in diameter without insulation for a Galant.

Well that 3.2mm diameter would be right if it was solid core wire, 8mm^2, which is about 8 gauge in AWG gauges.
But stranded wire, you can't really measure the diameter very well and it will be bigger.
It's stranded wire there isn't it?

Look at this table (below) and read the note at the top about the diameter info and equivalent cross-sectional area.
I really don't know how you'd measure the gauge of a stranded wire, but maybe you could count how many strands and measure the diameter of a few individual strands with a micrometer and add it up. Wire manufacturers show it as number of strands and gauge per strand. Allied Wire and Cable says "19 strands" and "strand size is 21" for their 8 gauge SXL wire.
21 must the the strand gauge I guess.

Yeah I'd be all in favor of putting 4 gauge or 6 gauge cable in there if you wanted to upgrade.
Like SGX-4 or SGX-6. I notice that these automotive engine compartment wires, the good stuff, always meets SAE J-1127 and they have 125 deg C temp rating.

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Link to the page where that chart came from - and it shows gauges all the way down to 40:

American wire gauge - Wikipedia

en.wikipedia.org

 

[sebas-1024]

Well that 3.2mm diameter would be right if it was solid core wire, 8mm^2, which is about 8 gauge in AWG gauges.
But stranded wire, you can't really measure the diameter very well and it will be bigger.
It's stranded wire there isn't it?

Look at this table (below) and read the note at the top about the diameter info and equivalent cross-sectional area.
I really don't know how you'd measure the gauge of a stranded wire, but maybe you could count how many strands and measure the diameter of a few individual strands with a micrometer and add it up. Wire manufacturers show it as number of strands and gauge per strand. Allied Wire and Cable says "19 strands" and "strand size is 21" for their 8 gauge SXL wire.
21 must the the strand gauge I guess.

Yeah I'd be all in favor of putting 4 gauge or 6 gauge cable in there if you wanted to upgrade.
Like SGX-4 or SGX-6. I notice that these automotive engine compartment wires, the good stuff, always meets SAE J-1127 and they have 125 deg C temp rating.

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Link to the page where that chart came from - and it shows gauges all the way down to 40:

American wire gauge - Wikipedia

en.wikipedia.org

Yeah, makes sense. But I'm ok with the wire the car has, was more curious than anything else. Thanks!

 

[sebas-1024]

I kept investigating on the issue today, checked continuity on some wires and fuses, and I basically have 2 things left to check (or so I think) before going to the alternator itself:

1. Generator Relay: this is a special 3-pin relay, don't really know how to test it to see if it's working or not. Anybody know exactly what it does and how to check that it's working properly? I read the function in the Service Manual but I have to admit i did not get it.

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Image 1. Generator Relay function according to Service Manual

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Image 2. Generator Relay (doesn't look particularly melted or anything to me)

2. Connection to the Generator Relay in the fusebox: I noticed that one of the 3 female connectors in the fusebox seems to be below the intended position, like it was pushed in or something, maybe the corresponding pin in the relay is not getting a good connection because of that. Would that make the alternator stop outputting charging voltage and current?

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Image 3. Generator Relay connection port in Fusebox (the one in blue is the one that looks pushed in)

I know you recommended going to an electrician, but I'm trying to go as far as I can with the diagnostic before doing so. Thanks for the help!

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[We're on Boost]

1. Generator Relay: this is a special 3-pin relay, don't really know how to test it to see if it's working or not. Anybody know exactly what it does and how to check that it's working properly? I read the function in the Service Manual but I have to admit i did not get it.

In 2018 I had been reading that the Alternator relay in these cars is actually not a relay at all. It is a diode. Maybe with a resistor in series (as shown by circuit diagram).
So I did some checking on mine with my multimeter, which has a diode scale on it. The diode scale will read the Forward Voltage of a diode, which will normally be somewhere around half a volt for diodes in general except for Schottky diodes.
Here are my pics and notes from then. The pic is taken to show how the "relay" pins are numbered 1, 2, 3, 4.

I confirmed with the diode scale on the Innova multi-meter that there is a diode between legs marked #1 and #3 on the “relay”. Meter diode reading was 0.575 volts. Reading is “OL” with the probes swapped. The other 2 pins aren’t connected to anything, not even ground.
The positions for legs 2 and 4 in the fuse box are empty – no connectors there. So the whole thing is made OEM to not use positions 2 and 4.
There might also be a resistor in series with the diode – it is shown in the circuit diagrams.

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Circuit diagram showing a resistor in series with the diode, from page 6-57 of the Chilton manual. Alternator circuits:

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So test between pins 1 and 3 on the relay with the Diode scale on a multimeter. You should get about 0.6 volts with the probes one way and "OL" or something similar the other way.
If the resistor is blown you should get "OL" both ways.


More pics, MD113566 is the correct part number for the OEM relay in the 1g DSM:

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Looking into the socket with a bright light, you can see that only 2 of the positions have metal contacts in them:

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[sebas-1024]

In 2018 I had been reading that the Alternator relay in these cars is actually not a relay at all. It is a diode. Maybe with a resistor in series (as shown by circuit diagram).
So I did some checking on mine with my multimeter, which has a diode scale on it. The diode scale will read the Forward Voltage of a diode, which will normally be somewhere around half a volt for diodes in general except for Schottky diodes.
Here are my pics and notes from then. The pic is taken to show how the "relay" pins are numbered 1, 2, 3, 4.

I confirmed with the diode scale on the Innova multi-meter that there is a diode between legs marked #1 and #3 on the “relay”. Meter diode reading was 0.575 volts. Reading is “OL” with the probes swapped. The other 2 pins aren’t connected to anything, not even ground.
The positions for legs 2 and 4 in the fuse box are empty – no connectors there. So the whole thing is made OEM to not use positions 2 and 4.
There might also be a resistor in series with the diode – it is shown in the circuit diagrams.

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Circuit diagram showing a resistor in series with the diode, from page 6-57 of the Chilton manual. Alternator circuits:

You must be logged in to view this image or video.

So test between pins 1 and 3 on the relay with the Diode scale on a multimeter. You should get about 0.6 volts with the probes one way and "OL" or something similar the other way.
If the resistor is blown you should get "OL" both ways.


More pics, MD113566 is the correct part number for the OEM relay in the 1g DSM:

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Looking into the socket with a bright light, you can see that only 2 of the positions have metal contacts in them:

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Damn, you know your relay-looking diodes. So I should then get ~ 0.5 V in one direction and OL in the other, that's with the "relay" disconnected, you can get a voltage drop without any charge on it?

I'm looking at the circuit diagram and the relay is just in case the charging light bulb or fuse 9 is blown and current can't get to the field coil in the alternator, right? My charging light does turn on so even if the relay is not working, it shouldn't matter as long as that circuit is intact, but I'll check anyway.
Thanks a lot for the detailed reply

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[We're on Boost]

Damn, you know your relay-looking diodes.

I do think it's pretty funny. Diode called a relay, even disguised as a relay, in a relay case with 4 pins, in a relay socket. Oh well!

So I should then get ~ 0.5 V in one direction and OL in the other, that's with the "relay" disconnected, you can get a voltage drop without any charge on it?

Yes, you do this measurement with the "relay" disconnected. The way this works is, the multimeter has a small battery in it of course to power things in the meter that need power. A couple of multimeter functions that need to have power from the meter put into the circuit are the ohmmeter function and the Diode function. That voltage drop across the diode is coming from a voltage that is applied by the meter. So there is actually a voltage on the diode while you are measuring it. The voltage you measure with the meter this way is called the Forward Voltage of the diode. That's standard terminology so you can google it and read about it all day long if you want !

I'm looking at the circuit diagram and the relay is just in case the charging light bulb or fuse 9 is blown and current can't get to the field coil in the alternator, right? My charging light does turn on so even if the relay is not working, it shouldn't matter as long as that circuit is intact, but I'll check anyway.

I think that's right, yes, and that's what it says in some documentation, somewhere.
It's a pretty important backup because having the whole thing depending on a light bulb and a fuse in series is kind of not very good.

 

[sebas-1024]

Hi, want to thank you guys for your help and close this thread up. I decided to just re-connect everything and see if the alternator was working by any chance, turns out it was, the only thing I did was changing the terminal that connects to the +B post in the alternator, guess the wire was corroded enough that it was preventing the alternator to charge the battery before I swapped it. I have a 100 A fuse on the way so I can replace those awful looking wires in the fuse-box soon, but everything else seems to be in working order. Thanks again!