Guy at dealer says higher-amp alt. may screw up elec. system

Aftrbrnr · Aug 7, 2004

I was getting the door handle on my car fixed yesterday I was also trying to figure out why my car's electrical system was acting funny. It seemed like the battery wasn't holding its charge, but they tell me its the alt. Now I have an underdrive pulley on, and I do have some high-draining devices installed (PIAA headlights, hi-power car audio) so the stock alt. is not only not making enough power apparently, but it is also fubared. I asked the guy if they could get me a higher-amp alt., but he says that getting one may damage the car's system. I should probably also mention I have under-drive pulleys installed, so that's an even bigger strain. But anyways, the man says that I should consult a mechanic/technician before I do the job. Now I'm more then certain a 130 Amp alt will not screw up your car, I mean that's what the newer SN-95s have in them. Or am I wrong here. . . . . .

cardudeusa · Aug 7, 2004

I have a 160A 3G alternator. It will not mess up the electrical system, you just have to rewire the power wire. I had a picture of how to wire it properly, gimme a minute maby I can find it.

Michael Yount · Aug 7, 2004

Go here and read up on it - www.pa-performance.com. Installed correctly, there is nothing to worry about. If you have underdrives, and more electrical accessories - that will cause more strain on the electrical system than having enough alternator to power things properly.

jrichker · Aug 7, 2004

Here's the straight story...

Here's websites with pictures of the 3G installation...

See http://www.geocities.com/smithmonte/Auto/3G_130A_Alternator_Upgrade.htm - all the tech data you could ever want to know
OR
http://www.mustangcentral.net/tech/alternator.html - excellent pictures of installation

For the right way to do the wiring. Some people will tell you that you can skip the wiring upgrade, but it will catch up with you sooner or later. A fire in the wiring harness is ugly and expensive.

Under no circumstances connect the two 10 gauge black/white wires to the 3G alternator. If the fuse blows in the 4 gauge wire, the two 10 gauge wires will be overloaded to the point of catching fire and burning up the wiring harness.

A larger alternator properly installed is an excellent addition to the pre 94 model Mustangs. I am running one and have NO problems.

jwzg · Aug 7, 2004

Someone was trying to impress you with their "knowledge" of an electrical system.

Aftrbrnr · Aug 7, 2004

I talked to a guy (someone who knows about cars) at the dealer. He says that there shouldn't be any problem, and that I shouldn't need 4G wire either. He says the only slight problem maybe mounting it, as the new alt maybe designed differently on the outside then the stock alt.

jrichker · Aug 7, 2004

Aftrbrnr said:
I talked to a guy (someone who knows about cars) at the dealer. He says that there shouldn't be any problem, and that I shouldn't need 4G wire either. He says the only slight problem maybe mounting it, as the new alt maybe designed differently on the outside then the stock alt.

If the alternator puts 130 amps and the stock wiring is only good for 60, doesn't that tell you something? Can you say smoke and fire?

The stock wiring is two 10 gauge wires. The National Electrical Code rates 10 gauge wire at 30 amps at 72 degrees. As temperature goes up, the current rating goes down. Two 10 gauge wires would carry only 60 amps at 72 degrees, only 50% of the output of a 3G alternator.

If you still have any doubts, repost & I will find the wire current capacity tables and either post them or a link to them.

Daggar · Aug 7, 2004

One small footnote to add: Just because you have a 130 amp alternator doesn't mean that you're pumping 130 amps through the wires. The amps across a wire is determined by the power draw of the components that are fed from that wire. You can install any size (power output wise) alternator into your car that you like and see no real difference in how your acts (assuming that all the components are stock). Where you may run into trouble is when you start adding more components and attempt to feed those components through wiring that was not intended to supply the extra load. Example: attempting to supply power to an electric radiator fan by tapping from somehwere off of the stock harness. If you plan to place a larger demand on the power system in your car then upgrading JUST the alternator is not the answer. The stock wiring was designed to handle the load of factory components and very little more.

Michael Yount · Aug 7, 2004

aftrbrnr - you need to find a different dealer to hang around. Neither of your contacts there is helping you any with their 'advice'. Richker is spot on - you're already taxing the stock system with the accessories you've added. The larger 4 gauge cable from the alt. output to the hot side of the battery (or starter if you have a mini starter) is necessary to help handle the alternator output when your accessories are drawing more current than the stock wiring can safely handle. This is not a place to skimp, or to move forward if you're not certain of what you're doing. Car fires are something that usually total the car.

TRWXXA · Aug 9, 2004

DO THE WIRING UPGRADE! Even if you don't plan on adding high-draw accessories.

After you start your car, the battery needs to recharge off the alternator. The battery will take just about all the current it can get in order to recharge. If you have a deeply drained battery (from leaving on lights, playing the stereo, or multiple cranking attempts), it may initially take most of the 60 or 70 amps the 3G alternator is putting out at idle speed.

As previously posted, that may be more than the stock wiring can handle.

Don't chance it. The wiring upgrade kits are cheap insurance. If you do nothing else, at least get 4 ga wire to bypass the stock wiring. However, I'd recommend getting a kit with an in-line mega fuse for maximum protection.

Ozz · Oct 27, 2004

Definitely upgrade the wires!

HISSIN50 · Oct 28, 2004

the guy might have thought you wanted to bolt in a hi-po alt alone (no wiring upgrade). were that the case, as everyone has repeatedly said, you would have issues (but the HVAC fan-load would be reduced when the harness fire was keeping you warm).

wake · Oct 28, 2004

electric fires are not pretty!!! The upgrade is well worth it!!!

bmorrisj · Oct 28, 2004

i used the 4awg wire and 200amp ANL fuse i already had inplace hooked up to my sub amp (jbl 1200.1) since i have no subs, i yanked the wire out of the car and put connectors on each end, on to the hot side of the starter solenoid and the other to the back of the alt....

Guy at dealer says higher-amp alt. may screw up elec. system

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