I recently installed a single wire gm and was wondering if all you guys use a fuse between the positive on the battery and the alternator output?
GM didn't put a fuse in between a single wire alternator and the battery in factory installations...I'd follow their lead.
Did GM even use a single wire alternator in OEM applications? I thought that was an aftermarket "innovation". Bob
I didn't, I think the output is somewhere around 80 anps. That's a big fuse. If you think you need to maybe a fusable link would do the trick.
My OT DD is a 2k model GM pickup with a 1 wire alternator for charging. There is a sense wite for reference voltage indication on the idiot gauge on the dash, but the sense wire is not required to make the alternator work. FYI - my 2k model gm pickup has a 105 amp alternator; sometime after then GM switched to put in 140 amp alternator. For on topic rides, 100-ish amps on the alternator should be way more than what's needed.
Autozone sells 100 ampere resettable circuit breakers. That's what I'm using in my 1-wire alternator circuit, and have had no problem so far.
Yeah I do!! I had "the sooo reliable " alternator shorted out inside and the heavy wire that goes to the battery immediately started smoking while moving in morning rush hour traffic. The engine quit and I lost PS. Every inch of the wire from the solenoid where it hooked to the battery system up through the cabin, through the ammeter and out to the shorted alternator was instantly smoking. It filled up the cab with smoke on my Willys P/U and scared the **** out of me. I was running an amp meter so the heavy wire ran through the cabin behind the dash board allowing me to reach under and break the circuit before the truck caught on fire. I lost a lot of skin from the burns in my palms but my truck was on the road in the afternoon. There is always a big argument about amp meters. If I had been running a volt meter I would not have been able to break the circuit and it could have burnt my truck down. (the wire would have been buried in a harness some place else) Mine was a 3 wire alternator so I don't blame the alternator **** breaks. It came stock on a 73 3/4 ton 4x4 Suburban with dual air. That experience convinced me to run a fuseable link in the line where it can be hidden in the harness. I even run one on my generator cars if I'm wiring it from scratch. I get the heaviest fueable link on the pegboard and use it. I have never had one burn out but if there is a problem as I described it will blow and save your car. A fuse or fuseable link is a safety device to protect the wiring and possibly the car and not there to save alternator. I don't know the rating of that alternator but it must have been pretty heavy duty. A replacement alternator and a replacement wire that included the fuseable link was replaced along with a replacement ammeter and AFAIK it is still going strong. You can get maxifuses but they are so ugly and hard to hide. (they are big) If you need to reset a fuse all the time you have a problem. I think Fords used fuseable links around the solenoid to protect the wiring. I get mine at the parts store. I think mine had a large terminal for connection to a bigger lug at the solenoid or battery. I'd run one on a generator or alternator with or with out an ammeter or volts gauge to protect the wire. I'm not paranoid enough to add them to a working system but if you are wiring from scratch it is a cheap addition that is worth the time and trouble. IMHO It probably won't happen to you but it could.
Nope, but I do run a volt meter on my dash. I don't think you can over amp your battery but you can over volt(over charge) it.
Yes- I'm using one of those big ugly maxis between my 1 wire and the starter post (which is then off to both the battery and the ignition switch bat terminal. Fire bad.
You can use a fusible link. Most all modern cars have one for the alternator. GM used fusible link wires in the charging system as well. Everything is your car should be fused except the main positive battery cable to the starter.
Fuses are installed to protect wires from an overload, meaning that the draw (amps) from the load (appliance) exceeds the capacity of the wire (the size or gauge). Under this premise, the only way an alternator needs a fuse is if either the battery or the alternator itself experiences a dead short. An alternator is not a load, actually the opposite is true, the battery is the load on the alternator. The only way a battery can get a dead short is a catastrophic failure like the battery getting crushed. It's true that if the alternator wire gets frayed and touches ground, a fuse would save the wire, but with such a short run how often would that happen?
In this case wouldn't the fuse protect the diods in the alternator? GM used a fusable link on its older cars but not between the battery and the alternator, it was between the main power source and the firewall/fusebox.
A fuse or circuit breaker would break the circuit in case of a dead short on the alternator side. It would depend more on how your rig is wired. If the main feed from the alternator goes back directly to the battery and then a secondary lead runs off the battery as does on most 70 something GM pickups it would keep a direct short in the alternator isolated to the alternator. On my 71 the main feed from the alternator goes to the junction block on the inner fender where it connects to the feed wire to the battery and the main feed for the rest of the truck which has a fuseable link a few inches from the junction block. That keeps all power going to the rest of the truck fused. On the diode thing, they usually get blown up because someone mishandled jumper cables or caused a spark in the battery circuit such as connecting the battery when there was a load on the system.
On cars, it's common to use a fuse link between the alternator and the loads/battery, but not a fuse or breaker.
I put a master disconnect switch in the p***enger compartment of my roadster as I like the broad range of protection it offers. It isn't a subs***ute for fuses, but when the un-fused starter armature shorted to ground, the current load welded the contacts in the relay, and the starter kept trying to run. I reached over, hit the disconnect switch,*and saved the wiring. I still burned my fingers on the starter relay (it didn't look hot).
Simple answer. 175amp mega fuse between alt and primary buss or battery on every car I build. As stated above "fire BAD". Have one electrical fire and you look for every way to pervent one in the future.
No, I don't use a fuse or breaker between the alt. and batt., but I have a battery disconnect switch mounted on the floor and I can easily disconnect my battery in an emergency, or when I park the car. After having my solenoid stick in on my daily driver, and fry the starter before I could disconnect the battery, I'm going to add a battery switch to it too!
Ditto, BigChuck. A fusible link won't open, if there is a momentary power surge,....fuses are more prone to. I went with the recommendation included in my wiring kit,...and I carry some spare "link" along with spare lamps and fuses. Protection is like cubic inches, torque, ***, and firepower..."MORE'S BETTER " !!!! 4TTRUK
You might want to visit Mark Hamilton's M.A.D. web site http://www.madelectrical.com/electrical-tech.shtml for info on a very good way to fuse the entire system, especially when using a rear (or remote) battery location and Ford-type starter solenoid. It does require more wire, but I like the fact the heavy + battery starter cable is "cold" except when starting, and everything else is fed through a maxi fuse, fusable link, etc, from the solenoid. While on his site, spend some time learning why the very popular 10/12SI alternators work much better when 3-wired, as designed. (The "sense" wire, when run properly, allows the alternator output to stay at 14.3 or so throughout the system, not just at the rear of the alternator, because of voltage drop). The "one wire" model was never intended for vehicle production, only stationary/industrial use, where very low loads and battery recharging were the only requirements, JFYI.
If you do instal a fuze in the line between the batt. and alt., you will need two of them. One to protect the wire from the batt. current and one on the other end of the wire for the alt. that will still put out current.
Fuses are breakers are available with various degrees of delay and over-current tolerance, but those aren't what's generally available. A piece of fuse wire is also much cheaper than an equivalent fuse and fuse holder, or breaker and connector.
I put in a Mega fuse. Yes, that is the real Bussman trade name. Ford's been doing it since the mid '90s so the fuses are easily found. IIRC I found it in the wiring diagram for a '98 Contour. Remember that fuses protect the wire, so fuse it matched to the wire size which should be matched to the current draw. Also remember most fuses are meant to have no more than 80% of their rating as the maximum normal current draw. Go above that and you are into the time/current trip curve where it will eventually fail. Look to marine supply catalogs for lots of neat DC wiring items that are weatherproof. http://bluesea.com/ has lots of good tech info. If your alternator fails it can go to a dead short and make the battery cable smoke. I have seen it, engine was not running at the time.
Fuses are cheaper than replacing melted wires in a wiring harness. The re-settable circuit breakers also work well.
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