[SNFU Mobile]

I have this in the heating/cooling forum as well, but I think it's a post in error - this should be the correct place for it.

Is it okay to run large loads, i.e. electric water pump and fan relays right off the output lug of the alternator? To me, this makes sense, and would prevent me from having to run more wire than necessary to complete this job.

Electrically, it's all the same, right?

 

[John_Muha]

As long as the lines are protected. Trying to see how one would put a fuseblock or circuit breaker in the line without bringing it over to the firewall, fender, or core support. Problem with trying to hang it in the air unsecured is vibration. Vibration can cause the wire to break off an unsupported fuse block.

 

[SNFU Mobile]

True - I see the point there. I guess I can just run it right off of the battery post - the water pump relay, that is, and just attach the assembly to the radiator support somewhere. As long as it's out of the way, I don't really care. I just don't know if I want a wire running from the engine to the radiator support - but I guess I already have one with the alternator.

Thanks John!

 

[Cecil]

Why not use a positive battery cable with the pigtail already wired? Comes straight off the battery with no additional work, and it'll look clean.

 

[SNFU Mobile]

It might be a little of an overkill for me, but it's not a bad idea. I can do it that way, use an isolating mount on the rad support, and pull power for the relays off of that - that would look clean! Thanks for the idea!

 

[JimN]

One of the reasons NOT to run things right off the battery post is that it messes up the ammeter gauge readings (I don't know what happens with an idiot light setup). The ammeter uses a wire that runs between the battery and the horn relay to measure the charge state of the battery. Running high loads from the battery terminal sometimes pins the ammeter and always gives unreliable readings about charge and discharge. A better way might be to use the horn relay lug to wire your high load stuff, and use a heavier guage wire (or double up the wire)from the alternator to the horn relay.

 

[SNFU Mobile]

True - but I'm not using an ammeter. I have just a straight voltage meter. I haven't found an ammeter that goes high enough for me yet, or I might slap one on there. Thanks though!

 

[JimN]

True - but I'm not using an ammeter. I have just a straight voltage meter. I haven't found an ammeter that goes high enough for me yet, or I might slap one on there. Thanks though!

Well another problem that I thought of is that when you run high loads directly from the battery post, you are still charging the battery through some wiring that wasn't designed to recharge at high load. So you may be overworking that wiring between the horn relay and the battery.

 

[SNFU Mobile]

Jim - I just looked at your post, and you bring up an interesting situation for me.

I don't have a horn relay, per say. I have re-wired my car with a painless 18 circuit kit, and added in the high amperage alternator kit. The horn relay is actually now part of the main fuse block - kind of a waste to have it all the way in the passenger compartment, but hey - it works great, and the Hella horns I added are incredibly loud - no problems there.

Anyhow - the way I have it set up now is there is the main wire run from the battery to the starter, it's about a 6 gauge, as far as I can tell. Then, there's another thick wire that runs from the battery, through a 50 amp "maxi" fuse, and into the fuse block. The alternator output is connected to the starter post where the battery is landed. So, I almost have to take it off the battery post, right? Or, I can put a relay kit with a thermal breaker in-line and run it right off the output of the alternator, and not have to utilize the wiring going to the battery. I believe this is probably my best bet, and just now, going out and looking at it, I think I really need to upgrade the size of the wire leading from my alternator to the starter post. I believe it's about an 8-10 gauge wire, and it's a 170 amp alternator. I don't think that's going to cut it.

Anyhow - sheesh, I'll stop rambling now.

 

[Peter F.]

Can you cut the wire coming from the alternator and put a bolt type terminal block into the wire somewhere where it's usable? You'd cut the wire and put ring terminals onto the cut ends to attach to the terminal block. I hope you know what I mean, the terminal block is a plastic base with a stud sticking out of it to bolt the wires onto. Should be available at a parts store.

The loads could be run off the alternator directly anyways by just running another wire. No big deal either way. Running another wire from the alternator splits the current to 2 wires instead of having all the current going through the one wire. However, you have to be careful operating the accessories with the engine off because you could overload the starter to alternator wire.

If you've got a 170A alternator I hope you've got about 4 guage running from the alternator. It's possible you could melt 6 gauge with that much current. Remember that the alternator only produces the current that's necessary so it could be fine with even a 10 guage as long as you don't try to draw too much current with an extra load or a short.

I've been thinking and looking at wiring in a car and I think 10 guage is good for about 60A, 8 guage is good for about 100A and 6 guage is good for about 140A. This is the wire with the good high temperature insulation. Cheap wire with 75 degree C insulation probably wouldn't cut it for these currents.

In all cases, make sure all of the wiring is protected with fusible links or fuses. Especially a fusible link at the starter because the wires are more likely to melt down around the starter.

Peter

 

[rb69]

I used MAD kit and they run from the alt. over to a junction on the rad. core support. From that point I power my relays for trans. brake, fans,elec. water pump.
That sounds like what you are looking to do.

 

[SNFU Mobile]

Yeah man, that's it! Do they have a kit that has the correct connector for the back of the alternator?