is the alternator wire on a 2007.5 LMM supposed to have a fusible link In line on the wire? Or is there just a fuse at the firewall?
Alternator wire fusible link 2007.5 LMM
- Thread starter Whiskyshark
- Start date
Okay thanks. I have been looking for a schematic like this. A mechanic told me he thought there was supposed to be an inline fuse. Would that mega fuse from the alternator break the circuit if it was over charging? I put on a new alternator, belt and two new batteries but when the truck sits overnight the battery reads 12.3 on the voltmeter. I wonder if thats okay or if that mega fuse cooks be bad? Thanks for your help!!
12.3 volts is not that far off from the batteries resting voltage. what do they read when the engine is running?
the fuses are not normally there to protect the alternator from over charging as they are self regulating to a degree and will limit current on their own. it's more for faults in the alternator that would allow current to back feed from the batteries into the alternator causing a short
the fuses are not normally there to protect the alternator from over charging as they are self regulating to a degree and will limit current on their own. it's more for faults in the alternator that would allow current to back feed from the batteries into the alternator causing a short
For the first 10 minutes when it’s running there in about 13.8 to 15.0. It fluxtuates a lot and then settles at around 14.4-14.5. Before I replaced the alternator the voltage was sometimes reading 9.5 before starting but it would start which makes no sense to me. I though it needed at least 12. So should I add an inline fuse at the alternator? I have read they have them to prevent fires
if it's not too cold out they can often start at around 10 volts if the engine and injectors are in good shape.
the voltage fluctuating is probably from the load management the ECM does with the alternator current and the turning on and off the grid heater and glow plugs. mine does the same thing
the alternator already connects to a fuse so I would not add or modify anything.
the voltage fluctuating is probably from the load management the ECM does with the alternator current and the turning on and off the grid heater and glow plugs. mine does the same thing
the alternator already connects to a fuse so I would not add or modify anything.
I definitely don't want to add or modify anything but it makes me par oid that the mechanic thinks it should have had an Inline fuse on it and someone removed it. The alternator wire was definitely cut and reattached before I bought it but not sure why
you may want to just replace the cable if it's been cut or altered.
the old systems generally ran the alternator right to the battery for charging and used a fusible link for protection. the newer setups will land the alternator wire to the fuse block
the old systems generally ran the alternator right to the battery for charging and used a fusible link for protection. the newer setups will land the alternator wire to the fuse block
I have been having trouble finding that wire. I called the dealer and they couldn't even give me a part number
When you say 'alternator wire' exactly which 'wire' do you mean? The cable that carries B+ power to the batteries? Connection to the ECM?
This one? The one that attaches to the back of the alternator that is red with a black stripe? There is no fusible link there. Part #20771932 https://www.gmpartsdirect.com/oem-parts/gm-battery-cable-20771932?c=Zz1lbGVjdHJpY2FsJnM9YmF0dGVyeSZsPTEwJm49QXNzZW1ibGllcyBQYWdlJmE9Y2hldnJvbGV0Jm89c2lsdmVyYWRvLTI1MDAtaGQmeT0yMDA4JnQ9bHQmZT02LTZsLXY4LWRpZXNlbA==
When you order the part, give them your vin# to make sure you are getting what you need.
When you order the part, give them your vin# to make sure you are getting what you need.
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Alright. Well thanks for the help. That makes me feel better. On a side note I just assumed a normal battery charge was closer to 12.6 and mine are 12.3 and seem to drop lower as it sits. I guess the last thing to replace is the mega fuse? I've replaced everything else and done a parasitic drain test
Batteries should be at 12.6 - 12.7 after charging and sitting for 24 hours or so. One way batteries can be bad is that they have shorting cell, and no amount of fuse pulling, wire testing, parasitic loss search, etc will tell you about that. If you fully charge your batteries, leave them disconnected and then check 24 hours later to see if both are at the voltage same level OR just take them to a shop (Walmart for instance) and ask them to test the batteries. Most of the Walmart people know that they have to disconnect the batteries prior to testing, but some don't. You may have to 'remind' them about that, assuming you don't remove the batteries yourself. You should not be at 12.3 and dropping. Something's wrong.
I put new batteries in my truck prior to driving from Kansas to Arizona and noticed on the trip that the alternator charge rate was always about 15 1/2 volts, and I knew that shouldn't happen based on the conditions at the time. I thought the problem was with one of the battery ground cables and I made a repair for that. Still had the constant charging problem. I would charge the batteries (both connected in the truck) overnight and the truck would start very quickly, alternator charge rate when running was 14 or so, which is where it should have been. . So I thought I was done. The next day, the charge rate was back to 15 1/2. So charged both batteries again, and then I disconnected one battery, started the truck, charging rate was 14, then disconnected 1st battery and the 2nd battery was very low, something like 10 volts. Turned out to be a shorted cell. So when the batteries were together, the bad battery dragged down the good one. When separated, you could tell which was bad. Replaced that battery and everything is A-OK, charging rate 14 or so.
I put new batteries in my truck prior to driving from Kansas to Arizona and noticed on the trip that the alternator charge rate was always about 15 1/2 volts, and I knew that shouldn't happen based on the conditions at the time. I thought the problem was with one of the battery ground cables and I made a repair for that. Still had the constant charging problem. I would charge the batteries (both connected in the truck) overnight and the truck would start very quickly, alternator charge rate when running was 14 or so, which is where it should have been. . So I thought I was done. The next day, the charge rate was back to 15 1/2. So charged both batteries again, and then I disconnected one battery, started the truck, charging rate was 14, then disconnected 1st battery and the 2nd battery was very low, something like 10 volts. Turned out to be a shorted cell. So when the batteries were together, the bad battery dragged down the good one. When separated, you could tell which was bad. Replaced that battery and everything is A-OK, charging rate 14 or so.
Oh wow okay. That sounds crazy. I wouldnt expect that but I will try it. I just bought these batteries a month ago so I assumed they were all good!
They MIGHT be, but you need to test them to see if they're the problem.
If they are good, the problem could be that they aren't getting charged properly; or they are getting charged, but are being discharged improperly (parasitic drain).
If they are good, the problem could be that they aren't getting charged properly; or they are getting charged, but are being discharged improperly (parasitic drain).