Electrical Failure

[Xavier]

Before I begin diagnosing this problem I would like to get other peoples opinions, see how other people would go about it.

On a beautiful Sunday afternoon which was only about 75 degrees, I went cuising in the Cobra. Suddenly the engine goes dead and I pull over to the side. At this time my fans are off, but when switched to on they both work (just wanted to see if it had current). I hit the hazard light button and nothing happens.

I get out of the car and immediately check the fuses, the following fuses are blown;

Main 50 amp
Gauges
Headlights

I replace the fuses, try to start the car. Nothing. This time nothing in the car will turn on - I have no electric any where. Thinking that what ever happened made my battery cut-off fail, I jumped the battery cut-off. Again, still no signs of electricity. I checked the fuses again - all fuses are good except the one for the gauges. It blows each time.

I noticed a couple other things as well (you always do when things don't work the way they should). The wire terminal going to the alternator from the main fuse look burnt, not bad, but definitely with a tad bit of black on the terminal to the main 50a fuse and to the alternator. Defnitely not what you would expect an 8 gauge wire to look like. The copper wire peaking out looks more like aluminum.

I finally had it towed home (2 miles) and begin to look at it again; all grounds are good, I checked all of them. Fuse for the gauges keeps blowing. Alternator is very hot, not boiling hot, but hot. I never touch it after running the engine so maybe this is typical? I noticed that the alternator was still very warm 4 hours after running the engine and running into this problem. I was surprised to see how warm it remained.

Tonight i start taking apart the dash and the steering column looking for a short somewhere. The gauge fuse seems to be a simple diagnostic of a loose or broken wire, but what has me more concerned is the alternator and the 50a fuse blowing.

Specs ar as follows;
Tuff Stuff Alternator 100amp
Painless Harness
Car has less than 4k miles on it
Ididit Steering column which has had had internal wire issues within it in the past (this is to no fault of the manufacturer). Major suspect...

[joyridin']

Are you sure the alternator doesn't have an internal short? Like maybe int he voltage regulator? This would cause it to stay hot, and might cause other stuff to blow fuses.

[Z-linkCobra]

Im with Joyridin' on that one. The alt. should be hot after you have been driving. The temp will depend on how much load you have on it i.e. stereo, fans etc. Staying hot after being shut off sounds like an internal short to me as well.Make sure your alt. is grounded well. Just because its grounded to the motor does not mean its grounded internlay to the case...Ive had that happen in the past.

As far as having no power at anything after you replaced that main fuse...thats interesting. Start at the begining...at the battery and work your way out from there.

If you didnt live so far away i would offer to help...lol. I like wiring.

[Xavier]

Thank you to both of you. My thoughts are this, and only after the 3 day weekend I will know for sure;

The Alternator blue the 50amp fuse and the others, such a surge went through the lines fast, and while it did not do damage, a bunch of fuses blew.

When I hit the switch for the hazard lights to go on, that brought on an existing problem in my steering harness I did not know I had. Which consequently blew the fuse for the gauges.

So I will disconnet the the steering harness from the curcuit and see if I get switch ignition without the fuse blowing. If I do, the steering harness is one culprit.

In regards to the alternator, I will pull it and send it off to the manufacturer for a test and/or rebuild. I know local guys can do the testing, but so many of those guys are clueless, and if it needs rebuilt it is already there.

The alternator is a 100amp, I have it grounded to the frame from the case, heavy wire, great ground - it is always the first thing I look at. I do not trust a alt. bracket for a ground. It was powering nothing at the time other than the engine and an MSD ignition. (no radio, no wipers, fans were not running).

Thanks again...

[Scoober]

You might have a couple of things going on here. I have a boat that had the alternator get so hot that it melted the boot around the power wire, it was because the connection was very corroded and acted like a resistor. New connector and worked great. The boat is not very old and only had 200 hours on it.

[Xavier]

Update--

Pulled the alternator, its a 75amp, not 100amp as stated. Anyhow, went to Autozone (against my better judgement) and they put it on their tester and it passed with flying colors. No issues they assure me.

The battery, a two year old Optima, was reconnected to find out I could not simulate any of the above scenarios....hmmmmm? Took a volt meter to it to find it only had 6volts dc coming from it. So bad coil in the battery? Again, I took the battery to Autozone and they will test it, but it must be fully charged first. Funny thing is I recognized the battery was dead last week, reading 3v. I put it on my Harbor Freight battery charger and charged it for 4 days, not only reading 36v after 4 days of charging?

This is my second Optima battery in this car in 4 years and only a few thousand miles, first battery was leaking with a bad coil. If it is bad I am going to be pi$$ed. If it is good, I will have no idea why it lost its strength seeming that the alternator is good. And yes, the Optima battery is 2 months passed its warranty. Great...

I go to pick the battery back with its testing results in a few hours, I guess I will see what happens then.

Scoober - thanks for the feed back. When pulling the insulation and wire loom from the exciter wire, I can see a 1/2" patch where the outside of the wire just wore through, nut cut, nut broken, but wore right through the insulation. I am going to go from a 10awg to 8awg and replace both wires for insurance. Leads on the exciter wire were brown, not terrible, but the copper was turned grey. Thanks for the input.

[RICK LAKE]

Xavier Forgot to ask, What size cable goes from the ALT output to the starter soleniod or battery direct?? You also need a 4awg with a 125-150 amp mega fuse in the curcuit. Your wiring is not big enough and causing charging problem. 10 & 8 are not big enough for 100 amp setup. If the wires are real hot, the system is under size. Try paperformance and get one of there wiring kits for alt output. There about 25-40 dollars depending on length of cable. Rick L.

[Xavier]

Rick,

I just found out it was a 75 amp alternator, not a 100 as originally stated. I am replacing the wire with a 8awg from a 10awg. Neither got hot, but the ends did not look good. I love fooling with the electrical and need to take a look at what I have again, I have a 50 amp protecting my fuse block, but nothing within the line to the battery. That could be my problem?

[RICK LAKE]

Xavier Any chance of a first name? Anyway 2 thing are used for gauging charging cable, amps and length of wire from point "a" to point "b". Alot of rod rebuilder use this for wiring cars with extra power needs. for a 65amp alt and an 8' run to main connection, #6awg is safe, can run #8awg but depends on load. 80 amp and up would be #4awg. Again you can get away with a #6awg. A mega fuse is a slow blow fuse to protect the whole car from a grounding of the charging cable, over charging ALT, or short to ground. I have seen these save wiring harness. 125 would be perfect for a 100 amp setup. 100amp would be ok for a 75 amp ALT. One other quest is how thw wiring is setup in the car. If all the power goes through the amp meter first like ERA, this is why you want heavier cable to handle the load. By running a output cable directly to the pos of the battery the amp gauge will not work and you have no idea about what's going on. This is why a volt meter is better in some cases. Again it's not period correct but neither is my car.
Battery's I am not a fan of the overpriced Optima batterys. The thing with them is mounting them in any position. As far as maintainance, the one I had, use to have a trickle charger on it when the jeep was not in use. Red top 2 1/2 years and bad battery. I run Delco or interstate batterys now. I still have a small trickle charger on the car when not in use. I can buy 2 delcos for the price of a Optima and almost the same CCA rating. I have never tryed a gel cell battery. Any way, this info is to protect your car. You can run less and alot do but,------. Rick L.

[Xavier]

Rick Lake;

Names Allen. Thanks for all of the posts and comments. I know about leads, electrical, amperage and size of wire; which makes it all more than embarrassing that I would get caught up in this regarding my electrical system. Although I have worked on cars before the Cobra, they were mainly stock hotrods, replace a part with the same part and you are pretty much good to go.

In the early build days of the Cobra, over 5 years ago, I made a lot of mistakes by listening to people and trusting vendors/manufacturers. Taking their word for their instructions, be mechanical or otherwise. I have replaced a ton of parts that were not good for my application, or were cool, but unreliable. I read something, I did it, and later on I found out that really was not the way to do it - or was just flat out lied to. Some of this is inexperience building a performance vehicle, some of this is just impatience. When I build my next car, I will save thousands of dollars in redoing.

Any how, it looks as though from all calculations I need a new alternator of at least 100amps, which I have to save for. If I am careful, and do not do too much, I can use the 75amp until I get a new one as long as I control excessive electronics. I have a new battery, of course you read that post. And I just figured out why my gauge fuse was blowing within my gauge circuit - bad tachometer (MSD ignition is fine). I will send it in to Autometer to get rebuilt. All other gauges and steering harness is good to go...thank goodness.

I do not have any protection between the alternator and battery now, which of course as you bring it up is completely obvious as to why you need it. If something would happen to the Alternator, bam, could blow the battery. And of course there is the size of the wire which is also completely obvious and needs to be upgraded when the alternator gets upgraded.

While I am re-looking at everything, I will clean my 3 ground connections, inspect the wires and upgrade to better thermal protection on some wires in the engine bay. I am also thinking about rerouting my wires in the engine bay to a new more protective, attractive location.

Thanks for the feedback...

[RICK LAKE]

Xavier Allen we all have been in that boat of building or buying parts that will not work as they are told about. I have better than 30 years of this and still have gotten caught with issues of parts not being up to what I was told. My car is over build for a reason. I have some double systems as backup incase of a primary failure like 2 fuel pumps. I use one most of the time but have switch over to give the other one a work out too. Most cars had fusable links in the old days to protect wiring. Today they have mega fuses in the 100 to 200amp range. 3,000 rpms on most car is where the charging system is measured for max charging. No alt will put out 100% all the time unless either a battery cell issue or too small of a supply wire to the car. Startup you see high readings because the Alt is recharging the battery plus suppling power to the whole car. This is some of the reason batterys are getting smaller and starters are using less ampage to start a car. 175 to 225 on the old days. gear reduction was started and everything has changed, for the better. Saving weight. Rerouting wiring is a good idea, make sure you have them not rubbing against any parts of the car and have clamps or clips about every 12" to keep wires from moving, rubbing, or vibrating. Vibrations internally break the wire and you don't see it. The resistance goes up and so does the power load on the Alt. I will try and give the best info I have or direct you to someone more knowledgable in that subject. There are some great guys on this forum that have alot of years of building cars and knowing what works and what is questionable. The best thing I can tell you is do your homework and ask alot of questions any time you can to other builder and manufactures. They are like Doctors, I always get a second opinion.You are going in the right direction. Good luck. 75 amp will be OK without all the power ideams on at idle. It also depends on how hot it is out too. Rick L.

[IndyCobra]

Couple of points, maybe you've already thought of them:

• What accessories do you have that would require a 100 AMP alternator? Have you calculated on paper what your total load would be with everything turned on? Maybe there's a short somewhere and that's why your alternator is working so hard? Just guessing but 75 AMPs seems like more than enough for a typical cobra with minimal accessories.
• Yep, you need a master fuse on the feed wire from the alternator for the reason cited. Voltage regulators go bad quite frequently and you need the fuse to protect the wiring, your battery, and the main bus.
• Fuses protect the wire, not the device so size your main fuse accodingly. You don't really need to go much larger than 20% larger than your maximum alternator size.
• For a 100 AMP alternator, you may need a 2AWG or 4AWG wire depending on the length of the run. I like to use welding cable from a local source. They usually crimp the ends on for free. The fact that your insulation is discolored points to the wire getting hot. Maybe it was just from the alternator overload but maybe it contributed to it as well as resistance goes up with the temperature of the wire.
• Sealed batteries like the Optima require different kind of trickle charging to keep them fully charged for anything not used on a regular basis. Not keeping them charged and not trickle charging them properly results in shorter battery life. Unless you race, you may find the performance from a wet battery to be more cost effective the next time you have to replace that Optima.

Like all advice, it's worth what you paid for it. Hope you get things up and running quickly.

[Xavier]

Indy,

Thanks for the reply, I had several threads listed what you went over in your reply. Everything you say I agree with and will have to make those changes within my system to make it completely reliable. 75 amps is something I can get away with most of the time if I watch it, but I do not think it would be reliable when I have everything on, in hot weather, and crusing speeds. The alternator manufacturer confirmed, I am pulling 35 to 45 amps at cruising speeds and I commonly have at least 1 fan on and commonly drive with my headlights on during the day to avoid people not seeing me in a low profile car. I think the 75amps is the misleading part, and where I have gotten in trouble looking at this on paper - the fact is, it is rarely on 75 amps (if ever). If you add up my under-sized wiring, under-sized alternator, under charged battery you can see how this all leads to a problem. The 75 amp has been "getting me by" but I know, and could not live with, this being a unreliable system. I do not want to go down the road thinking what I can turn on, and what I cannot. Sure, it has been this way for a few years, and this is the first failure, so I do not want to make a mountain from a mole hill, but at the same time, I want it to be fun, reliable and safe. I am certain you know what I mean.

I will redo this part of the electrical system, make it completely over built and bullet proof so that not only can I drive the car, but I can be at peace when doing it (and acutally enjoy it).

Thanks for your reply Randy.