swankstar
SILVER Star
Recently setup a dual battery system and had some trouble getting the solenoid to work correctly. Shorted a couple things since I was trying to get things done too quickly (as usual). This led to replacing a couple parts (the solenoid that connects batteries and the alternator) and trying again, this time with the charge battery positive DISCONNECTED while working on the system -_-
So, with replaced alternator and solenoid, I fired up the truck expecting to be a happy camper with two charging batteries while the rig was running, and two separate batteries when it's not running. That is not what I had at all.
With all these new parts, the system STILL wasn't charging completely/correctly. I was getting about 13.2V from the charging system, which didn't make much sense to me. It's kinda charging, but not really. How does that even happen?? And I was getting about 0.9V from the "charge lamp" circuit @george_tlc clued me into for actuating the dual battery solenoid. This also didn't make sense (why not 12+ volts??).
Well, off to the internet to learn a little about the charge system and if there are any fuses or relays I could investigate. Sure enough, there is a "charge relay" or something located here (FJ, not sure if FZJ is the same?):
Also, I may as well note at this point that the wire used for actuating my second battery solenoid came from terminal 2 of the 7.5A "CHARGE" fuse. This is supposed to energize shortly after the engine is running, once an actual charge is being produced by the alternator. I'm still not clear on the benefits of NOT having both batteries turn over the starter, but many of the threads/posts/articles I found before doing this claim connecting the batteries before engine fire up is less than ideal.
Anyway, back to the relay.
Mine was a gray plastic cube. I pulled it out and like any good non-electrical person does, shook it. Didn't hear anything. But look, it has little tabs holding a lid on, I'll check that out.
What I found inside was this:
ALL FOUR of the solder joints in the red oval were broken. All the copper legs were free to move as they saw fit.
I checked for resistance between all of the legs, and found that from blue to blue it would go from a couple megaohms to open when I would move the relay around a little (don't ask me why I thought of trying this, I don't really even now what that means, I just saw somebody on tv do it once), and the same thing from red to red:
I figured that can't be good and decided to try re-soldering the joints. First attempt was just re-melting the existing solder but I didn't really like how that ended up so I did it again and added a little solder. Turned out looking ok. I think a big factor in it working out is the circuit board pads are nice and big, hard to mess that up
:
After jiggling the legs and feeling confident they will at least last another day, I decided to put the guts back in the housing and test out.
Snapped everything together and went to turn on the truck. A NEW DASH LIGHT APPEARED. I have not seen this light since owning the truck (July of this year)!! It's a little red square above the voltmeter in the dash. Hmmmmmm. Anyway, started up the rig and that light promptly went away. Went under the hood to check the system and sure enough, now I was getting full charge (14.4V) to main battery, the dual battery solenoid was getting energized so now both batteries were getting charged (first time since installing the second battery), and nothing smelled like o3.
The one thread I found about replacing this charge relay was from years ago and talked about it being a discontinued part then, and since it was long after hours anyway, I figured I better try fixing it.
Turns out if you aren't getting a red light above your dash voltmeter, you better check this thing out!
So, with replaced alternator and solenoid, I fired up the truck expecting to be a happy camper with two charging batteries while the rig was running, and two separate batteries when it's not running. That is not what I had at all.
With all these new parts, the system STILL wasn't charging completely/correctly. I was getting about 13.2V from the charging system, which didn't make much sense to me. It's kinda charging, but not really. How does that even happen?? And I was getting about 0.9V from the "charge lamp" circuit @george_tlc clued me into for actuating the dual battery solenoid. This also didn't make sense (why not 12+ volts??).
Well, off to the internet to learn a little about the charge system and if there are any fuses or relays I could investigate. Sure enough, there is a "charge relay" or something located here (FJ, not sure if FZJ is the same?):
Also, I may as well note at this point that the wire used for actuating my second battery solenoid came from terminal 2 of the 7.5A "CHARGE" fuse. This is supposed to energize shortly after the engine is running, once an actual charge is being produced by the alternator. I'm still not clear on the benefits of NOT having both batteries turn over the starter, but many of the threads/posts/articles I found before doing this claim connecting the batteries before engine fire up is less than ideal.
Anyway, back to the relay.
Mine was a gray plastic cube. I pulled it out and like any good non-electrical person does, shook it. Didn't hear anything. But look, it has little tabs holding a lid on, I'll check that out.
What I found inside was this:
ALL FOUR of the solder joints in the red oval were broken. All the copper legs were free to move as they saw fit.
I checked for resistance between all of the legs, and found that from blue to blue it would go from a couple megaohms to open when I would move the relay around a little (don't ask me why I thought of trying this, I don't really even now what that means, I just saw somebody on tv do it once), and the same thing from red to red:
I figured that can't be good and decided to try re-soldering the joints. First attempt was just re-melting the existing solder but I didn't really like how that ended up so I did it again and added a little solder. Turned out looking ok. I think a big factor in it working out is the circuit board pads are nice and big, hard to mess that up
:
After jiggling the legs and feeling confident they will at least last another day, I decided to put the guts back in the housing and test out.
Snapped everything together and went to turn on the truck. A NEW DASH LIGHT APPEARED. I have not seen this light since owning the truck (July of this year)!! It's a little red square above the voltmeter in the dash. Hmmmmmm. Anyway, started up the rig and that light promptly went away. Went under the hood to check the system and sure enough, now I was getting full charge (14.4V) to main battery, the dual battery solenoid was getting energized so now both batteries were getting charged (first time since installing the second battery), and nothing smelled like o3.
The one thread I found about replacing this charge relay was from years ago and talked about it being a discontinued part then, and since it was long after hours anyway, I figured I better try fixing it.
Turns out if you aren't getting a red light above your dash voltmeter, you better check this thing out!
