Starter relay and engine wiring

[Dino]

I am upgrading the alternator and bypassing the ammeter and I need to run a heavy wire from the alternator to the batt bolt on the starter relay.  Does anyone have a clear picture of the relay itself and maybe the rest of the under hood wiring?  Mine is all tangled and I would like to fix that.  Also, what size eyelet do I need on the starter relay?

[Pete in NH]

Hi Dino,

I can't help with a picture of wiring on a 69, but the starter battery bolt connection would be a 1/4" ring terminal. You can get them for various wire gauge sizes. What size alternator are you planning to run?

[Dino]

Hi Dino,

I can't help with a picture of wiring on a 69, but the starter battery bolt connection would be a 1/4" ring terminal. You can get them for various wire gauge sizes. What size alternator are you planning to run?

Thanks Pete! 

The alternator is a USA Industries model A1345.  It's basically a denso 90 amp meant for a late 80's and newer Dodge.

This is the one I got: 

http://www.ebay.com/itm/USA-A1345-Alternator-88-89-Chrysler-Fifth-Avenue-Dodge-Truck-/320918431932?viewitem=&sspagename=ADME%3AL%3AOU%3AUS%3A3160&item=320918431932&vxp=mtr&nma=true&si=kZ%252Fphvgjnp5OziZjG2lSAQU6DWo%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

I decided on that one after reading about DKN's, Myk's and 2Gunz's conversions here:

http://www.dodgecharger.com/forum/index.php/topic,19802.0.html

I would like to run a wire to the starter relay and I can either get a 6 gauge or double up a 10 gauge like 2Gunz did.  If I run it over the intake manifold I think a 6 gauge would work. 

I had this in mind but I guess the eyelet's too big.
http://www.ebay.com/itm/140938950521?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

[John_Kunkel]

but the starter battery bolt connection would be a 1/4" ring terminal.

Actually 5/16".

[Dino]

Is it okay to use a 3/8" eyelet or does it have to be 5/16" ?

[MaximRecoil]

Is it okay to use a 3/8" eyelet or does it have to be 5/16" ?

It is indeed a 5/16" stud on the starter relay (1/4" stud on the alternator though). You can use a 3/8" ring terminal if you want, especially since the starter relay stud has an oversized nut; mine does at least (9/16" instead of the usual 1/2" nut that accompanies a 5/16" stud), but it is better to just get a 5/16" ring terminal; they are common.

When running a heavy shunt wire from the alternator stud to the starter relay stud (which effectively is running it directly to the battery, because there is already a heavy factory wire from the starter relay stud to the battery), you should have a fusible link on it, placed at the starter relay stud. The fusible link should be about 3" long and 4 sizes smaller than the wire it is protecting. For example, if you are running an 8 gauge wire from the alternator to the starter relay stud (which is heavy enough for about a 60 amp alternator), use a 12 gauge fusible link.

With my 318, the most obvious path to take was in the valley between the passenger-side valve cover and the intake manifold (this is where a factory harness was already running, and there are flexible metal wire hold-downs already there), and then along the firewall (again following an existing bundle of wire using existing wire hold-downs) to the starter relay. It took 4 or 5 feet of wire, plus the fusible link.

[Pete in NH]

Hi Dino,

I stand corrected on the 5/16 " stud on the starter relay, so much for trusting my old eyes. When in doubt -actually measure!

When you parallel two wires of the same gauge you in effect drop two wire sizes. So, two #10's in parallel equal a #8. Two #8's would equal a #6. I think a single #6 would likely look a little neater. As Maximum said that would take a #10 fusible link section if you can find one but, I'm not sure what the melting point of that #10 link would be other than really high. As far as I know Maxi-Fuses only go to 80 amps, but I think I would feel more comfortable with the 80 amp Maxi-Fuse, than that #10 link. High current stuff really scares me in its potential for serious damage.

[MaximRecoil]

When you parallel two wires of the same gauge you in effect drop two wire sizes.

Three wire sizes actually, but wires are most commonly available in even sizes, so that rule of thumb tends to get rounded in practice. Two 10 gauge wires in parallel = the same total cross sectional area as a single 7 gauge wire, which calls for an 11 gauge fusible link (which is probably impossible to find). Of course, that's all on paper, which assumes wires are manufactured perfectly to spec. In reality wires vary in size from manufacturer to manufacturer, sometimes by quite a bit, especially when you get into the larger sizes like 4 gauge and bigger. For example:



Those are both supposed to be 4 gauge wires; the one on the left is battery cable from my local autoparts store, and the one on the right is power cable from KnuKonceptz, a car audio company. If you want to see something really drastic, look at the comparison photos in this thread.

[Dino]

Holy cow look at the difference in those!      The 4g wires in that link are so far off it's not even funny.

Since I would have to change the eyelet anyway I may as well just find a 6g wire and get some 5/16 eyelets.  Pair that with the maxi fuse? Oh darn, I don't know the size of the one on the alternator.  I'll have to measure the stud tonight.  I don't have a rubber boot to protect the alternator eyelet, are those alt specific or pretty generic?

Will the 80 amps maxi fuse do the job with a 90 amp alternator?  I know they sell 100 amp fuses but the inline holders only go up to 80. 

Thanks for the help gents.

[MaximRecoil]

The alternator stud size is 1/4". You don't need a rubber boot, though it won't hurt anything if you want to use one. There are already exposed high current terminals in your car, such as the positive battery terminal and the starter relay stud.

If you want to use a fuse, and you want bigger than 80 amps, you can get ANL fuses, and the sky is pretty much the limit on amperage for those. They are pretty expensive though, as are decent holders for them.

The easiest thing to do is use a fusible link; you would want 10 gauge to protect a 6 gauge wire. You may be able to find a roll of 10 gauge fusible link wire at your local autoparts store, enough to make lots of 3" fusible links, and if not, it can be found online easily enough. The idea is to protect the 6 gauge wire from melting and causing a fire in the event of a dead short that pulls full battery amperage through that wire. It is pretty much fail-proof; i.e., if the current being pulled through your 6 gauge wire isn't enough to blow your 10 gauge fusible link, then it certainly isn't enough to melt your 6 gauge wire, thus no fire. 

Aside from accidental miswiring (user error), this is extremely unlikely to ever happen, provided you route the 6 gauge wire properly so that it is not chafing on something metal that will eventually scrape through the insulation. Car accidents are the most likely cause of a fusible link coming into play, because the crumpling steel chassis can easily pierce a heavy hot wire, and clamp it to ground tightly, suddenly pulling ~900 amps from your battery. If the wire isn't protected and it catches on fire, it could be very dangerous if there is leaking fuel nearby. 

The easiest way (as well as the proper way) to connect a fusible link to your 6 gauge wire is to get a 6-to-10 gauge step-down butt connector or a parallel splice connector (use a ring terminal on the other end of the fusible link of course). Use an indent crimp for either type of connector. If you don't have a proper crimp tool for firmly indenting a 6 gauge connector, soldering is an acceptable alternative.

[Pete in NH]

Dino,

My choice would be to use the 80 amp Maxi-fuse. I think it's better to be over protected- 80 amp fuse on a 90 amp alternator. Remember it's not like at 81 amps the fuse will melt. These types of fuses are generally specified at carrying a 200% overload for some number of seconds before melting. Fusible links do offer a level of protection but I think real fuses are a more refined and controlled type of protection. I like the Maxi-Fuse because they are readily available. Some other types of high current fuses I'm sure would be as good or perhaps better but not as readily available.

Also, on the covering for terminal connections, You can use various sizes of heat shrink tubing. The unshrunk tubing should not be over twice the size of the final diameter you want. Those low cost electric heat guns used for striping paint make good heat sources for shrinking the tubing.

[tan top]

  have a look at these pictures below  , these any good ? , its of a 69 coronet R/T  basically same under hood except for vacuum lines ,

can take  as many pictures as you need  of mine , but not much of the wiring & routing ,  is looking stock now under there .

[elacruze]

Don't use a ring terminal, use a proper wire lug with heavy duty shrink wrap.

http://www.delcity.net/store/Standard-Copper-Lugs/p_1015.h_92017.t_1

[Dino]

Did I mention you guys rock?      

TT those pics are perfect, it's exactly what I wanted to see.      I wonder why the owner mounted the tubes on the water valve upside down though??  Is this normal for coronets? 

I'll use the wire lug with a solder slug and shrink wrap.   

I think I'll go with the maxi fuse, seems to be a good solution.  Do you find that running a 6 gauge wire is sufficient or overkill?  I do plan on running it in the stock location.  My only concern with not having a rubber boot is the small distance between the alt stud and the engine block.  It may be fine I'm just paranoid about these things.  I do have shrink wrap so that's definitely an option.

Thanks again folks, your help is invaluable.

[Dino]

Almost forgot, any recommendations on an aftermarket wire loom?  I really don't like that corrugated plastic stuff I have now.  Anything out there that looks good, protects the wiring and is easily applied?  Yes I do like to have my cake and eat it.  At least I didn't ask for cheap.   

[elacruze]

http://www.powerstream.com/Wire_Size.htm

[WHITE AND RED 69]

As far as the wrap I like this stuff. Just slides right over the wiring and looks a lot better than the plastic tubing. They also offer a classic line that looks kinda like stock but costs a bit more.

http://www.summitracing.com/parts/prf-70902

[Pete in NH]

Dino,

That copper wire lug is just the thing you want. If you find a way to get it crimped on with the proper crimper it will be bullet proof. You might be able to find a local electrician, automotive electrical shop or electrical supply house who would crimp a few terminals on for you. Remember to put the shrink tubing on before you crimp on the final lug! When you start getting into the lower number wire gauges you'll find this size of wire in house service entrance systems and industrial wiring, so an electrician may be able to help you.

On the #6 gauge wire, it's about the right size for a 90 amp system. In a lower voltage system like a 12v system you want to minimize voltage drops in the wiring. a #8 gauge would handle the current but might get a little warm at times. Detroit would probably use the #8 and save money. #4 would have even lower losses but, that is a little bit of over kill. In a low voltage system it's not about how much current the wire can carry safely as much as how much energy do you want to lose along the way.

[John_Kunkel]

Running a heavier gauge wire from the alternator, down the valve cover to the starter relay, then to the starter and eventually to the battery involves multiple "connections" which our resident expert has proclaimed are problematic.

An alternate route would be directly from the alternator to the  battery terminal via the core support.

[MaximRecoil]

Running a heavier gauge wire from the alternator, down the valve cover to the starter relay, then to the starter and eventually to the battery

"Then to the starter and eventually to the battery"? No; directly to the battery from the starter relay stud, via the heavy wire that is already there from the factory - link.

By the way OP, that factory wire from the starter relay stud is only 8 gauge, so if you choose the route of alternator stud to starter relay stud, and you use 6 gauge wire, you might also consider replacing the aforementioned factory wire with a 6 gauge wire, else you will partially defeat the purpose of using 6 gauge wire from the alternator stud to the starter relay stud.

involves multiple "connections" which our resident expert has proclaimed are problematic.

Who is the "resident expert" who proclaimed that? In any event, the connections in this case are all ring terminals on studs, clamped tightly with a nut, which is the best type of connection there is. They are not "problematic".

An alternate route would be directly from the alternator to the  battery terminal via the core support.

This would work fine as well, but since it doesn't follow any factory wiring route, it would look odd / out of place. Appearance may or may not be a concern, depending on the preferences of the owner of the car.