Ok guys, I need some electrical gurus in here. My car for the past few weeks, has just been blowing fuse after fuse. This is the ignition fuse. It's a 40amp fuse, and I do have a 3800 supercharged. The fuse is pretty hot usually if it doesn't blow, and when I pull it out it's pretty toasty. Well tonight it blew it again, and I am just clueless. Anyways, it doesn't seem like it's shorting out, because if it's getting hot obviously something is causing it to just heat up and then just blow finally. I have a 2 gauge power wire for the car now, so I fixed all that. Then again, do you think I somehow just have too many things hooked up on the ignition fuse, and it's just finally giving out after so much usage. Would it hurt to run a 50amp fuse in place of the 40amp one, since I have the proper 2 gauge power wire running to it? Let me know what you guys think, because it's not like I'm hitting a bump and it's dying, it's a gradual process usually after the car warms up and I drive for a bit, so I think it's just heat soaked and gives out. Give me your thoughts as electrical stuff is just so hard to diagnose.

Thanks!
Amir

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1 of 2: Factory Maroon/Gray 87 GT 5 spd: 2.8L (Best 1/4 mile: 15.57@87mph, 2.0 60ft)
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You could have the circuit overload and as the electronic parts heat up they'll draw more power and blow the fuse. Or there could be a wire or something that short out as your car bounces around on the road. Either way the fuse will be hot if you get to it soon enough after it blows.

If its in a stock fuse box then the 40 amp fuse is in there because the stock wiring on that circuit can't handle a current draw of more then 40 amps. But if you'd changed the wiring around then it hard to say how unsafe it would be to run a 50 amp fuse.

I would take some of the item off that circuit and give them another connection to the battery, just make sure you have on that connection too.

Yeah but as far as overloading the circuit, if I am, the 50amp fuse should be perfect for it. And with my power wire upgraded to the 2 gauge wire, that should be more than safe enough to run that kind of a fuse. I could always take something off the circuit, but if this indeed the problem, I don't the difference. I guess what I am saying is, can't a 2 gauge wire handle quit a bit of amperage? That's why when I upgraded my power wire from a 10 gauge wire to a 2 gauge wire, I figured that should be more than hefty to handle any more draw and a larger fuse. Anymore input? I was going to test it in my garage by running the car to see if it was drawing anymore power and if that 50amp fuse was getting hot, I didn't plan on driving it just yet.

Thanks.
I am very frustrated with this problem, as I have my car running and now electrical!

Amir,
Why are you having so much trouble lately ???
I thought you had it in and running with a 5sp then put in a girlie tranny.

so what happened??? oh and the front end??

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88 GT, 3800SC, Getrag 5sp. 12" Vette Rotors,Custom stuff done

quote Originally posted by revin: Amir, Why are you having so much trouble lately ??? I thought you had it in and running with a 5sp then put in a girlie tranny. so what happened??? oh and the front end??

Because I have bad luck I guess. There is no such thing as a bolt on product anymore. The rotors, that was a nightmare. Bought a whole new set of front rotors after warping them thanks to grinding on the lower control arm. Then having to replace my tubular uppers with stockers so it would clear the caliper. Then having to smack my lower tubular control arm after grinding the crap out of it. Now I have big brakes, wow what an ordeal. Now this fuse popping thing. Car is all ready to rock, getting ready to put my TOG headers on, and true dual exhaust and I should be on my way to high 11's. When's the next show, cause I'm coming damnit!

If your running a 50amp fuse in the stock fuse box I'd say your always gonna have trouble. The connections will deteriorate faster in the fuse box the more amps used. Most stock boxes I've been around never have more than a 30amp fuse in them.

quote Originally posted by Butter: If your running a 50amp fuse in the stock fuse box I'd say your always gonna have trouble. The connections will deteriorate faster in the fuse box the more amps used. Most stock boxes I've been around never have more than a 30amp fuse in them.

Beside for point above, the 2 gauge wire should be able to handle the 50 amp fuse. So you might want to consider using a better fuse holder, like the ones sold for car audio.

Exactly which fuse keeps blowing , the one marked ECM IGN. The 10 amp fuse in position #1?

You have 2 gauge wire running directly into the fuse box, and more 2 gauge out of the fuse box into circuits elsewhere? If not, it's probably not safe to swap the fuse.

A fuse is designed to be the weak link in the system. Things get overloaded and it blows safely and protects the rest of the system. DONT put in the 50 amp...........its asking for trouble. You can either find and fix the problem by checking individual branches of the circuits downstream, or take some load off that fuse. If you used 40 amp and a 10 amp you would have all the capacity of the 50 amp plus all the protection of the 40.

Well I tried the 50amp fuse, and it didn't blow. I probably put 75 miles on my car today with it. No problems at all. The fuse is a little warm, but it seems to be just fine. Everyone keeps saying I'm stupid for running a 50amp fuse in the 40amp slot. The 2 gauge wire should be perfectly handled to run that fuse. I mean it's not like I jumped from a 40 to a 80. If that was the case I'd be a bit worried. And upgrading my 10gauge wire to the 2 gauge wire, I think it is pretty safe to run the 50amp fuse. Let me know your guys thoughts, as it seems that the circuit just seems overloaded I guess you could say. Is there a way to test the amount of amperage draw from the fuse block, so I know if it is over 40amps to that fuse? Let me know.

Later.

Well, it's over 40 amps since the 40 amp fuse blew, you know that. If I were you I'd run some of the circuits off that 40A through another fuse to offload some of the current. Where are you finding these 50A fuses anyway?

I'm confused - where in the heck does a Fiero have a 40 amp fuse?

quote Originally posted by Rare87GT: Well I tried the 50amp fuse, and it didn't blow. I probably put 75 miles on my car today with it. No problems at all. The fuse is a little warm, but it seems to be just fine. Everyone keeps saying I'm stupid for running a 50amp fuse in the 40amp slot. The 2 gauge wire should be perfectly handled to run that fuse. I mean it's not like I jumped from a 40 to a 80. If that was the case I'd be a bit worried. And upgrading my 10gauge wire to the 2 gauge wire, I think it is pretty safe to run the 50amp fuse. Let me know your guys thoughts, as it seems that the circuit just seems overloaded I guess you could say. Is there a way to test the amount of amperage draw from the fuse block, so I know if it is over 40amps to that fuse? Let me know. Later.

Im not sure you have solved the problem. If the 50amp fuse is now warm you still have a problem. Will the fuse blow just by having the key on for awhile? Does it need to be running? What to you have on the circuit?

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" DRIVE IT LIKE YOU LOVE IT"

quote Originally posted by Phil: I'm confused - where in the heck does a Fiero have a 40 amp fuse?

Phil, I have the Grand Prix Fuse block. It has a couple of 60amp fuses, 40amp fuses, so forth. It seems it must be over 40amps. The thing is, is it going to hurt with the type of wiring I have now? If I was running 10 gauge wire, then I think it would be unsafe. But how can a 50amp fuse be unsafe with 2 gauge wiring? I have my HIDs, Fuel pump, fan, electric water pump, stereo, so forth. I have been trying to work on seeing how many amps I have. As I asked before, how do you check to see how many amperages I'm pulling with the car running. It is blowing the fuses after driving, not just sitting it seems.

Beg, borrow or steal an amp meter ( most small volt/ohm/amp meter will have a 10 amp testing mode) Check each one of the major users of that fused circuit and see how much each one draws

quote Originally posted by Rare87GT: But how can a 50amp fuse be unsafe with 2 gauge wiring? I have my HIDs, Fuel pump, fan, electric water pump, stereo, so forth.

I'm having a hard time understanding exactly how your car is wired, but I think you are setting yourself up for trouble ... as in FIRE trouble.

A fuse must be sized according to the smallest gauge wire that it supplies. I find it hard to believe that you actually have 2 gauge wire running all the way to your fuel pump, your fan, your water pump, your HID lights, and your stereo. (2 gauge wire is heavier than the OEM battery cables!) For example, if the wire connected to the fuel pump is 14 gauge, then you must use a fuse appropriate for 14 gauge (not 2 gauge) wire for that entire branch.

You can begin an engineering review of your problem by adding up the rated current consumption of all the devices connected through your "problem" fuse. A circuit must be designed for the "worst case" condition, with all devices operating at the same time and all drawing their maximum rated current. Then both the wire gauge and fuse must be selected to support that maximum total load.

At the very least, you probably need to split some of your high-current devices (e.g. the water pump) onto their own separately-fused circuits.

[This message has been edited by Marvin McInnis (edited 03-10-2006).]

quote Originally posted by Marvin McInnis: I'm having a hard time understanding exactly how your car is wired, but I think you are setting yourself up for trouble ... as in FIRE trouble. A fuse must be sized according to the smallest gauge wire that it supplies. I find it hard to believe that you actually have 2 gauge wire running all the way to your fuel pump, your fan, your water pump, your HID lights, and your stereo. (2 gauge wire is heavier than the OEM battery cables!) For example, if the wire connected to the fuel pump is 14 gauge, then you must use a fuse appropriate for 14 gauge (not 2 gauge) wire for that entire branch. You can begin an engineering review of your problem by adding up the rated current consumption of all the devices connected through your "problem" fuse. A circuit must be designed for the "worst case" condition, with all devices operating at the same time and all drawing their maximum rated current. Then both the wire gauge and fuse must be selected to support that maximum total load. At the very least, you probably need to split some of your high-current devices (e.g. the water pump) onto their own separately-fused circuits.

Just my main wire going from the battery to the fuse block is 2 gauge. Everything else is normal gauged wire. We will take the water pump and put it on it's own circuit. I just didn't think running a 50amp fuse could possibly cause a problem. But I guess everyone has different views on that.

Well everyone can have their opinion, but Marvin is absolutely correct. Let's say you have 14 gauge going to your fuel pump for example, which branches off that 50A fuse. Somewhere along the line you hit a bump and the 14 gauge gets pinched and goes to ground while the fuel pump is running. Let's say 50A of current are going through that wire to get to ground. The fuse won't blow, but the wire will get hot enough to melt the insulation and start your car on fire. If there were a separate accordingly-sized fuse for that branch, the fuse would blow.

Since our cars always start on fire anyway, it may not be a big deal, but I try to avoid electrical fires as a rule of thumb.

quote Originally posted by Rare87GT: But how can a 50amp fuse be unsafe with 2 gauge wiring?

quote Originally posted by Rare87GT: Just my main wire going from the battery to the fuse block is 2 gauge. Everything else is normal gauged wire.

Aha! Then your 50 amp fuse and your 2 gauge wire have nothing whatsoever to do with each other. The only purpose of a fuse is to protect the wiring "downstream" of the fuse ... between the fuse and the device(s) at the end of the wire(s). Of particular note, a fuse is never properly used to protect the downstream devices ... just the wires themselves.

quote Originally posted by Rare87GT: I just didn't think running a 50amp fuse could possibly cause a problem. But I guess everyone has different views on that.

It's not about different views, and it's not about you or me being right. It's about helping you with your wiring problem, and it's about leaving correct information in this thread for people who may visit it in the future.

[This message has been edited by Marvin McInnis (edited 03-10-2006).]

At a minimum I would be concerned that the terminals and cross connects used to "wire" the inner workings of the fuse box would not be happy with that kind of draw. If the slot says 40, then 40 it is. Without specs you have no way of knowing when you will over fuse the box and burn it up. I would assume there is some head room worked in but, again, without specs it’s a guess.

Don't take this the wrong way but to me you are "moving" your fuse. The fuse, as stated by another poster, is the weak link in the circuit. It’s designed to fail when the circuit shorts to ground or draws to much current powering devices. Pulling that much sort of "moves" your "fuse" out to what ever link is weaker than your 50A (true) fuse. The shame is, as also previously stated, that if the new weak link fails you have good chance of a fire.

I have seen it happen. I once watched a buddy (of LONG ago) burn all the insulation off a run of 14G wire that he decided to use when he connected in an electric radiator fan. Worked great, for like 15 seconds. The fan’s current draw overpowered he ability of the wire, it started to get hot, and the insulation flashed away. It was kind of cool watching the smoke trace along the length of the wire. He also overused it so much that it continued to draw power, and burn off insulation, even after the bit zip tied to a metal roll cage burned up and provided a direct path the ground. I guess the paint on the bar helped prevent a “direct”, all out, connection ground.

Here is an alternative and rare situation which I have encountered a few times. If the crimping on the wire/fuse connection in the fuse block leading to the fuse is developing high resistance, it will generate heat. If the heat generated is high enough it will cause the fuse to blow. Additionally, once a crimped connection develops heating from resistance, it is an escalating situtation where the heat causes more oxidation in the joint, increasing the resistance, increasing the heat and so on. Evidence of this will be improvement when uprating the fuse but then a gradual return to the same fuse-blowing behavior.

Two ways to check. First, look at the connections in the fuse block - if you see evidence of heating (discoloration,saggy insulation, etc.) you have found a problem. Second, if you use an ammeter and it shows the fuse blowing at lower thant he fuse rating you probably have found a heating problem.

repeat, this is rare, but it has driven me crazy a few times.

This is a rather confusing problem. Not being just a government employee I was, and still am a qualified electrician for over 34 years.

You are right when you say that 2 gauge wire can easily handle the 50 amps of current. 2 gauge in the household wiring is rated at 100 amps and that is inextremely long cable runs, usually from the street to inside your fuse box which runs upwards of over 200 feet. In your short run and if you are using automotive cable then this wire is rated upwards up to 200 amps continiously.

Now someone mentioned that you removed the 40 amp fuse and replaced it with a 50 amp fuse. This part is troublesome because if the holder is only rated for 40 amps then you have increased the current by upwards of 25% by putting a 50 amp fuse in. The wire is capable of it however the actual fuse holder is not.

I see this a lot when people upgrade there kitchen by replacing the 14 gauge with 12 gauge. They then up grade the circuit breaker from 15 to 20 amps. In thinking they have changed the wire to handle 20 amps as 12 gauge is rated for 20 amps, they have also replaced the circuit breaker, however they always forget to replace the plug itself which is not rated for the 20 amp circuit. They are unable to strip the wire and use the slide in connector so they wind the wire around the terminals and think nothing is going to happen. Wrong number one cause of electrical fires. They should have replaced and upgraded the plug for 20 amps.

In your case this might be part of your problem for the fuse being warm. I doubt that you have a short as any short that is capable of blowing a 40 amp fuse will also blow a 50 amp fuse or burn the wire which is causing the short.

If we think about welding steel it is basically 17-30 volts dc current with upwards of 40-50 amps. You then keep the arc going by allowing the dc current to flow to ground with the welding rod super heating the steel and burning up. If you had a short the 50 amp fuse would have allowed enough current to arc and literally weld itself by burning up the shorting circuit.

Now saying this, there is a lot of good advice in these postings, that you should follow.

I would get or borrow a clamp on amp meter with everything running, it will tell you how much current is going through the fuse protected wire. Clamp on meters are like the jaws of a lobster and accurately measure the current flow going through your wire with all the usual accessories on.

If when you do this, and turn on and off accesories on your vehicle and get proper readings then you are ok. remember volts times amps equals watts. Thus inversely if you turn on your headlights at 55 watts each plus 24 watts worth of parking lights then we add the two times 55 plus 24 and divide by 12 to see a current draw of a little over 11 amps. I would always calculate your voltage as 12 volts. In determing draw we add up wattage and divide by 12 (volts) to get current draw in amps.

In thinking, I would guess that the lights draw 11 amps when on. Brake lights draw 3 amps each and you have either 4 or 6 of them for about 12-18 amps. Lets now add the air blower for another 10-12 amps depending on speed. Ignition when running takes about 15 amps with 2-3 amps for the computer alone. Radio depending on type is 10-15 amps. And lets never forget the rear window defogger which is about 30 amps. Wipers about 10 amps, cruise at about 3 amps, oh i forgot the fuel pump 8-10 amps and the fuel injectors at 3 amps per bank.

To just turn and run the ignition we are using 15 amps for the coil and computer, another 5 amps for the fuel injectors plus 8-10 amps for the fuel pump. If the front fan comes on we use 5-8 amps for the rear fan and 15-20 amps for the front fan. As you can see we have easily exceeded the 40 amps for which you placed the fuse in for. With the fan on we are running a little under 50 amps.

When you look at it this way you see that we really use a lot of current in our vehicles. This also explains why the alternators are rated for 97 amps in order to replace the current which we consume depending on running conditions, braking and temperature.

Now with out getting off topic, borrow, buy,steal, buy and return, a clamp on amp meter, if your current ratings are normal then you are OK, if not then check each circuit one by one until you locate the shorting or overloading wire. I should point out that as motors etc get old they get worn, out of round sticky and thus require upwards of 50% more current to do the same thing. We really see this in our power windows, replace the motor and clean up all the connections and you will be amazed at how fast they actually go up and down.

The previous posts are correct in regards to a cheap amp meter, however I have never seen these in line meters ever go over 20 amps and the majority are only 10 amps. My really good fluke is only 20 amps and I use the clamp on meter for simplicity and ease of use. If you use a regular amp meter you must disconnect the circuit and place the amp meter in line or in series with the load wire in which you are testing.

Good luck and at least you are using fuses and not automotive circuit breakers which are rated upwards to 60 amps and reset after cooling down.

tim

Is there an amp meter that can measure how much amperage is going throughout the ignition fuse slot? I'd like to be able to test it with something that can handle that much and know for sure which wire is sending my car over the limit. As most in the stores only go up to 10 or 20amps? Do you just check how much amperage with everything on, and how does it work, as I've never tested it before. Thanks guys, I appreciate the help.

[This message has been edited by Rare87GT (edited 03-10-2006).]

quote Originally posted by Rare87GT: Just my main wire going from the battery to the fuse block is 2 gauge. Everything else is normal gauged wire. We will take the water pump and put it on it's own circuit. I just didn't think running a 50amp fuse could possibly cause a problem. But I guess everyone has different views on that.

Well, try it for a while. If your car burns to the ground, we'll know for sure.
Personally, I wouldn't take that risk on my car.

As for testing it, if you don't have a 50 amp ammeter, you'll have to test each load individually. If any of them are more than 20 amps, though, even that may not work. You already know the load on the fuse is between 40A and 50A, so you really don't need to measure that. You've probably got a bad connection drawing power somewhere, or too much on that one circuit.

I don't understand how they work, but:
http://www.electronicstalk.com/news/exe/exe100.html
http://us.fluke.com/usen/products/LH2015.htm?catalog_name=FlukeUnitedStates&Category=CLMP(FlukeProducts)
Looks like they measure DC too. Sometimes I wish I had one; my Fluke 179 will only do 20 A.

quote Originally posted by Formula88: Correct me if I'm wrong but don't clamp on ammeters only work on AC current? They're inductive pickups, and there is no induction field around a DC wire because the voltage is constant.

I don't have any details, but I've seen Hall Effect clamp-on ammeters that are specifically designed to measure DC. I imagine that they are still quite a bit more expensive than conventional passive clamp-on AC ammeters.

Your second statement is only half correct. There actually is a magnetic field around a wire carrying a DC current (thus spoke Maxwell!), and its strength varies directly with the current through the wire, but it is constant ... so a simple passive clamp-on ammeter can't measure it. A Hall Effect sensor can directly measure the strength of a non-varying magnetic field.

[This message has been edited by Marvin McInnis (edited 03-11-2006).]

quote Originally posted by Marvin McInnis: I don't have any details, but I've seen Hall Effect clamp-on ammeters that are specifically designed to measure DC. I imagine that they are still quite a bit more expensive than conventional passive clamp-on AC ammeters. Your second statement is only half correct. There actually is a magnetic field around a wire carrying a DC current (thus spoke Maxwell!), and its strength varies directly with the current through the wire, but it is constant ... so a simple passive clamp-on ammeter can't measure it. A Hall Effect sensor can directly measure the strength of a non-varying magnetic field.

Yeah I guess I worded it wrong. There is a magnetic field, but no induction because the field is static, not continuously rising and falling as it does on AC current.

I'm not familiar with the Hall Effect ammeters, but then I've been out of that part of the industry for a while.

quote Originally posted by Marvin McInnis: I don't have any details, but I've seen Hall Effect clamp-on ammeters that are specifically designed to measure DC. I imagine that they are still quite a bit more expensive than conventional passive clamp-on AC ammeters. Your second statement is only half correct. There actually is a magnetic field around a wire carrying a DC current (thus spoke Maxwell!), and its strength varies directly with the current through the wire, but it is constant ... so a simple passive clamp-on ammeter can't measure it. A Hall Effect sensor can directly measure the strength of a non-varying magnetic field.

I have one. I don't have the brand name handy, BUT it was about $85, measures AC and DC current
and is more accurate than I thought possible. It is now a must have in my tool box.
Fluke has them (partial to Fluke). About everybody sells them now. Get one that has
good overload protection if you can swing it.
TG
BTW, ARE YOU SURE you don't have something running all the time, like a blower fan or something?
Something isn't right. Even if the fuse pops at 40, you shouldn't be running that close to the edge. That's overload territory. You aren't backfeeding another circuit somewhere are you?
Anyway,
GLuck.
tg

[This message has been edited by TennT (edited 03-11-2006).]

Partial to Fluke as well.. I don't think I will ever own any other brand of DMM. If you can borrow someone's that'd be your best bet. Without testing to see actually how much current is actually going through that wire it's just taking shots in the dark.
And Marvin's correct, the two links I posted are for Hall Effect clamp meters. The reason cheaper clamp meters can't measure DC is because they measure magnetic flux (probably just by inducing a current in a wire inside the clamp?), not the actual magnetic field.

Well we figured out what the problem was. The wiring harness going from the fuse block to the engine was riding on my exhaust manifolds back above the starter. I'm pretty happy we caught it before the wiring got completely disconnected. That was it though, 8 or so wires were shorting out. Thanks guys for all your help as we finally located it before I started driving it again!

I'm glad I have this forum to turn to!

Following wires and lookie what we found.

Thanks again,
Amir