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| 1991 Metro LSi main fuse problem; Need help | |
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| Tweet Topic Started: Jul 8 2015, 07:39 AM (1,948 Views) | |
| eljones | Jul 8 2015, 07:39 AM Post #1 |
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Fresh Fish
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I have a 1991 Geo Metro LSi which I drive every day. I used the AC last year with no issues. This year I ran the AC for about 10-15 minutes and noticed that it was not very cool. I guess I have a coolant leak someplace. While driving the car for those 15 minutes with the AC on the car cut off completely. I pulled the main fuse box cover and noticed the 40A (#6 in pic) was blow so I replaced it. Thinking that the low coolant may have been stressing the compressor I turned the AC off and and have not used it since. Once I started the car it drove for about another 10 minutes and blew the 40A again, luckily I bought 2 of them so I replaced it and needless to say it blew again. (ac still off) I had to get the car home so I replaced the 40A (#6) with one of the 30A (#7) LOL of course that didn't work long and then the 60A (#5) blew but I did get it home. I had the alternator rebuilt after this happened. They replaced all of the worn and bad parts inside of it except for 1 thing which they said tested ok, I can't remember what part inside the alternator that was and their closed all this week so I won't be able to find out what that one part was that they said was good inside the alternator. After the rebuild I was able to drive the car about another 10 - 15 minutes and again the 40A (#6) blew, which, when I keep replacing it eventually blows the 60A (#5). I think the main problem may be the 40A which is causing the 60A to blow. Both of them cause the car to cut completely off. Here's are my questions: (1) For the 40A (#6) what is it wired to? Perhaps that part is causing a short someplace. (2) What is the 60A (#5) wired to? Again, I think it only blowing because of the 40A which I think may be the real issue. (3) What can I do to fix this problem?
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| Old Man | Jul 8 2015, 09:15 AM Post #2 |
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Here is MY question: How did you find and post the pic with all the fuses numbered without reading the numbers explanation below it? anyway. To answer your questions. The below fuse boxes With the explanation of where all the fuses go to listed below their pic is at the (referenced below) thread. Note that not only the fuse box on the fender but also the fuse box under the dash are referenced here. http://geometroforum.com/topic/5018841/1/ |
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| eljones | Jul 9 2015, 07:44 AM Post #3 |
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Fresh Fish
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Yes, I did see that chart. But what didn't make sense was that my 91 LSi fuse box cover says 40A but that chart says 50A. Also, I didn't understand why a fuse that controls the "horn" would cause the cars electrical system to shut down and the car shut to completely down as well. No electrical power anywhere, not just the horn. I've had cars before and when the horn fuse blew just the horn didn't work - not the entire car. Can anyone give me some ideas about that? My 91 Lsi fuse box cover reads as follow compared to that chart. 5 - (60 Amp) 6 - (40 Amp) not 50A 7 - (30 Amp) not (40A 8 - (30 Amp) Edited by eljones, Jul 9 2015, 07:54 AM.
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| myredvert | Jul 9 2015, 09:21 AM Post #4 |
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myredvert
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First of all, I get the impression that this issue is beyond your experience and comfort level with electrical system problems. Fusible links are some serious circuit protection, and it takes a potentially serious problem to blow one. And never ever EVER continue to replace one more than once without first identifying and correcting whatever is causing it to blow. Even though we realize you have nothing but good intentions, in reality what you have been doing is quite frankly the equivalent of trying to burn your car to the ground. Even if it doesn't start a fire it is very possible it is causing more and more damage to wiring each time you replace and blow it, and will increase your risk of a bigger problem sometime in the future. I would suggest you seriously consider having your car towed (yes, I said towed) to a professional to diagnose and correct the wiring problem that is causing this before you burn your car to the ground and possibly hurt someone in the process. Tracking down electrical problems like this can not be done by looking at pictures and replacing fuses. You need a Factory Service manual for your specific year, or at least have enough knowledge and experience to use one for similar year but have enough experience to recognize when a wiring color or circuit may be slightly different than yours. While the "horn" (or a particular component of the horn system) may be one item that particular fusible link protects, it is certainly not the only one. In any case no "picture" or chart or whatever should ever be used blindly by itself without considering it's particular applicability, in other words, what exactly does it apply to and "does it apply to mine?" And when a problem i serious as your is, it would be wise to verify for yourself the accuracy of the information you use to work on your car. And "pictures" are just not suitable tools for diagnosing a short or other problem that is causing a major fuse to repeatedly blow. It can some level of familiarity, but it should never be mistaken for a diagnostic tool. In my 91 and in the 1994 FSM that fusible link powers items such as the Fuel Injector fuse and the Ignition Switch, and from the Ignition Switch also powers various fuses in the junction block. It's just my opinion, but I think it would be wise for you to get the car to someone with much more experience with electrical systems - the risk reward associated with type of problem isn't very favorable for "beginners" to practice on diagnosing more serious problems. Best of luck!
Edited by myredvert, Jul 9 2015, 09:23 AM.
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| eljones | Jul 9 2015, 01:31 PM Post #5 |
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Fresh Fish
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Thanks, yes I know a picture in this case "is not" worth 1000 words. What I wanted to avoid was the expense you advised of having someone track down the "short". I figured someone in the forum may have had this problem and could tell me exactly which circuits (part) this 40A goes to. That way it would narrow down the search process tremendously. Let's say for instance someone said it actually controls the compressor and the alternator. Then I would know to check those wires from the fuse to those parts and to also check those parts. Instead of checking every wire in the car or paying someone to do it. I do appreciate the advice. Perhaps I just didn't ask my question clear enough or gave maybe way too much information when I put up the initial post. I guess what I should have asked was this. Does anybody know what the #6 (40A) controls in a 91 LSi ? Because it has to be more than just the horn.
Edited by eljones, Jul 9 2015, 01:35 PM.
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| Old Man | Jul 9 2015, 02:21 PM Post #6 |
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Get a Factory Service Manual and start tracing out the wiring. No one here can trace out your wiring by watching our computer monitors. You gotta help yourself sometimes. |
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| myredvert | Jul 9 2015, 02:29 PM Post #7 |
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myredvert
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No, no problems whatsoever with either of those things actually. I think you painted a very clear picture of your symptoms and your electrical system experience. The fact that you were asking the questions you were asking, and didn't fully comprehend the actually complexity of what you were asking and think there is some simple one word forum answer that will make you instantly understand what all draws it's power from that fusible link tells us you are in further over your head than you realize. That fusible link along with the others supply power throughout the car, and not just to "the horn" or "the wipers" as you apparently believe it does. Not to be too blunt, but if you were capable of doing what you believe you could do in the manner you believe you could do it... ...you would know enough to have found the answers to your own questions already. Good luck to you! I do hope you realize we are really trying to help you, and would hate to see you burn your car to the ground becasue you tried to do something yourself that you just don't seem experienced enough to do, that's all. If you think you can handle it, get the correct wiring diagrams for your car, and like Old Man said, trace through your system until you find the short/problem. Edited by myredvert, Jul 9 2015, 02:39 PM.
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| myredvert | Jul 9 2015, 03:12 PM Post #8 |
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myredvert
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Here, I'll give it my best to answer your question... Something that you don't seem to understand is that the Fusible links in the fuse box are "major" distributors of powered throughout the electrical system. For example, the fusible link you seem to be having problems with in particular feeds: The radiator fan fuse and fuel injector fuse. Then it has a power feed connecting to the ignition circuit and depending on the key position then feeds as many as six individual fuses in the junction block - the ACC, WIP, BACK, IG, DEF, and HTR fuses which in turn power anywhere from one to more than a dozen individual components EACH, for a total of something like 20 or more circuits/components/systems throughout the entire vehicle from front to back receiving power from this fusible link - depending on how your particular car is equipped. And the fact that the fusible link was repeatedly blown without correcting the cause of the problem to the point where it also started causing additional problems with the main fusible link suggests you may have experienced damage to additional circuits in the process. I hope that you don't take this the wrong way, but the irony is that you don't yet seem to know enough about what you don't know to know that by the way you describe what you think you know that we probably know what you don't know better than you know. And we would all hate to see something really bad and extremely expensive happen to your car in the process... that's all. Edited by myredvert, Jul 9 2015, 03:22 PM.
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| eljones | Jul 22 2015, 10:22 AM Post #9 |
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Fresh Fish
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Thanks myredvert. Your July 9th, 4:22pm answer was exactly what I was looking for with my subsequent and follow-up questions. Now I "know" what I asked and definitely do not what to spend the time tracking the problem myself. Oh well, guess its time to sell the baby. Too bad, just put a motor and trans in her a few years ago . Thanks again. |
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| myredvert | Jul 22 2015, 11:35 AM Post #10 |
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myredvert
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If your engine and trans are good and you are otherwise happy with the car, why not take it to a professional to track down your wiring issue? |
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| freegeo | Jul 22 2015, 12:24 PM Post #11 |
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It is a shame you want to give up! There maybe a way to try and track it down. At the very least you should call around and see what it would cost to have it checked at a electrical shop. The fusible link blows but no other fuses blow? That's interesting. |
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| t3ragtop | Jul 22 2015, 01:17 PM Post #12 |
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Turbo3 and Twincam Tweaker
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to answer your original questions, the 60 amp fuse protects against a charging system error where the alternator output goes high. the stock alternator is rated for a 55 amp output, the fuse keeps the 6 gauge charging wire from melting. the 40 amp fuse is the main fuse for the car's electrical system and largely serves to protect the fuse and relay rack's buss. i have seen many failures of the fuse and relay rack where the steel buss bars crack and corrode causing resistance to go high enough that it produces heating of the buss system to the point where the plastic housing melts. pull the 2 mounting screws out of the relay rack and flip it over for inspection. the 6 gauge wire from the alternator has a quick connect on the fuse and relay rack end which snaps into the bottom of the rack. that connection point corrodes and causes a high resistance that can cause system errors. and lastly, any of the relays mounted on the rack (or in front of it in the little auxiliary mount) can fail causing bits of the coil pole shading to short the relay out. if you don't want to troubleshoot the problem you can use the shotgun approach and replace the entire fuse and relay rack including all the relays and fuses with another complete unit. that would be plug and chug. the relay racks come in 2 flavors, a/c and no a/c so get the one that is appropriate for your car. those are like picking blueberries at any junkyard that has metros. another known failure point for the electrical system is under the left front fender where the wiring harness passes through the "a" pillar/ door post into the cabin of the car. there is a big rubber gromett that isolates the wiring. if it fails the wiring harness can chafe and short out against the body. after the harness passes through to the inside it terminates at the interior fuse block. i have seen some of the interior fuse blocks short out, too. that is typically the case when the 40 amp fuse keeps clearing like it does in your case. any of this repair shouldn't be hard or expensive with available junk yard parts. you will have some time in it but i could fix something like that for under $100. the thing is that you need to get on it before your car just burns down. when you are dealing with 60 and 40 amps, bad things can happen very fast. your repair time and cost will skyrocket if you melt the wiring harness into a blob.
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| freegeo | Aug 1 2015, 01:31 AM Post #13 |
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to answer your original questions, the 60 amp fuse protects against a charging system error where the alternator output goes high. the stock alternator is rated for a 55 amp output, the fuse keeps the 6 gauge charging wire from melting. So if someone puts a higher amp output alternator in, do they need to upgrade the wiring and fuse then? I'm not an expert at wiring upgrades and would like to learn more. Edited by freegeo, Aug 1 2015, 01:32 AM.
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| t3ragtop | Aug 1 2015, 02:05 PM Post #14 |
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Turbo3 and Twincam Tweaker
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definitely, if you increase the alternator's output you need to run a cable that will handle the increased current. you also need to install a fuse that will protect the new cable. in general, you use a wire which has a ampacity that exceeds the output of the alternator and then install a fuse holder with a fuse that is rated for the current output from the alternator. as long as the wire ampacity is capable of handling the output of the alternator and the fuse size is under the wire's ampacity there's no danger of melting the cable. ![]() if you look at the oem alternator output cable you will see that is a rather coarse twisted wire arrangement. it's also not guite a 6 gauge wire diameter. the fewer strands of copper wire allow the cable to work harden pretty quickly which makes the cable prone to conductor breakage under the insulation. sometimes an oem cable isn't able to carry the 60 amps of the factory alternator and the increased wire resistance causes the cable to heat up. then at the fuse block there's that white nylon snap in connector. those turn green with corrosion which makes it one more high resistance connection. i've seen many, many cables with those white connectors blackened and burnt. when i upgrade to the 105 amp cs130 alternator i use a 4 gauge cable that has a bunch of very fine copper wires spun together that is fused for 100 amps. that cable is connected directly to the positive battery post. that gets the big current directly to the battery. then i connect the factory 6 gauge cable from the fuse and relay rack to the positive terminal of the battery and let the original 60 amp fuse in the rack provide the protection for it. that way the car's chassis wiring and fusing operates unmodified and as designed by the factory. you also need to provide a ground circuit cable that can handle the total output of the alternator so i run another 4 gauge cable from the negative post on the battery to the lug on the transmission replacing the original ground wire with a larger diameter wire. |
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| freegeo | Aug 2 2015, 12:54 AM Post #15 |
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Thanks for the reply. That explains a lot. |
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