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Car Forum / Porsche / Porshe 944 / September 2006'84 944 Electrical Problem - New Clue?
I'm still trying to hunt down a short somewhere in my '84 944 that causes the battery to go dead in a matter of a few days if I don't disconnect it. Based on advice from a previous post I've already hooked up my meter and tried disconnecting all the fuses one by one in an attempt to isolate the problem but was unsuccessful. Apparently the short is not contained within one of these circuits. I also tried disconnecting the stereo but that didn't help either. A visual inspection of the vehicle's wiring showed no apparent fraying or shorts. I think I may have a new clue. When I was out for a drive last nite I noticed that the alternator idiot lite would glow dimly when I put my headlites on. This lite appeared to glow brighter as I turned on more electrical devices (i.e., the fan, high beams, lighter, etc.) and increased the load. Does this tell me anything to help isolate the problem? Can there actually be problems somewhere in the charging circuit / system that is causing this situation? I'm really having a problem shooting this one down. Any additional advice would be appreciated. Cheers! You could have a partial short through the voltage regulator. This is a solid state device on the back of the alternator. It can be replaced for twenty to thirty dollars. Could be the reason the fault light is coming on. Or you could take the wires off the alternator and see if you are still seeing a short from the battery to ground as a test. I once had the alternator fault light come on. I had the alternator rebuilt and replaced the voltage regulator. Still had the problem. Then I replaced the fault light board. Still had the light. Finally installed a volt meter in the clock hole and disconnected the alternator fault light. Everything OK for the last three years. I still do not know what was causing the problem. >I'm still trying to hunt down a short somewhere in my '84 944 that >causes the battery to go dead in a matter of a few days if I don't >disconnect it. Based on advice from a previous post I've already >hooked up my meter and tried disconnecting all the fuses one by one in >an attempt to isolate the problem but was unsuccessful. Just a few comments - 1. Your earlier post said you had a 100 ma drain measured at the battery. That's .1A , which with a 60 AH battery will last 600 hours or 25 days. Your battery might be larger than that and IIRC, the 60 AH spec is at C/10 rate, i.e. at 6 amps. Batteries will give up even more at the low drain rate you are seeing. Your drain rate looks high, but it shouldn't kill the battery in a few days. 2. You are seeing the alternator idiot light, and it gets brighter with more load. That's a sign that the alternator is not putting out sufficient current to meet the load, much less charge the battery. I'd be looking first at the charging/alternator system, not the 100 ma drain. Check your charging voltage. If you aren't charging properly the engine starts will kill the battery and the load will eat up the rest. After you're sure that the charging is up to spec, then you can decide if you really have an excess load. You could look at the current draw through the different wires connected to the positive battery terminal to help isolate it. I hope this helps.  SignatureT o d d P a t t i s t (Remove DONTSPAMME from address to email reply.) Just a guess - did you check if the glove box light is on? Signaturejoliett -------- >>I'm still trying to hunt down a short somewhere in my '84 944 that >>causes the battery to go dead in a matter of a few days if I don't [quoted text clipped - 27 lines] > > I hope this helps. Hey Todd! The 100 ma drain was just attributed to the radio. The actual total drain is much larger which causes the battery to go dead in a few days. Someone had suggestrd that the radio might actually be a bigger problem so I totally discoonected in just in case (with no luck). Cheers! > >I'm still trying to hunt down a short somewhere in my '84 944 that > >causes the battery to go dead in a matter of a few days if I don't [quoted text clipped - 31 lines] > T o d d P a t t i s t > (Remove DONTSPAMME from address to email reply.) I'm also sure it's not the glove box lite or, unfortunately, anything that simple. I had hoped that by pulling each fuse one by one and checking I could at least isolate the problem somewhat but no luck. I'll try disconnecting the alternator to see if that makes a difference. If not, does that mean the problem must be with a relay somewhere? Most everything else should be covered by a fuse, rite? Thanks again! >The 100 ma drain was just attributed to the radio. The actual total >drain is much larger which causes the battery to go dead in a few days. What is the actual drain then? Just pull off the battery plus cable and stick your ammeter between the cable and battery. I think I saw that you have multiple wires going to +, so measure each one to find out which one has the big load, then check again with all fuses pulled. I know you've done some of that, but I'm not sure of your numbers. Also, what is your charging voltage and what voltage is the battery at when dead? If you truly have an excess load when turned off, it's easy to measure. Another thought - are you sure your starter motor is OK? It can look like a bad battery when it's just hard starting. The starter can be so bad that it looks OK at fully charged, but will fail to start with the battery even slightly discharged. SignatureT o d d P a t t i s t (Remove DONTSPAMME from address to email reply.) Why not remove the alternator and take it to a specialist and be sure it is working OK,if you have high mileage it could simply be a need for new brushes. When charging the voltage should be 13.5 to 14.volts. Alec >>The 100 ma drain was just attributed to the radio. The actual total >>drain is much larger which causes the battery to go dead in a few days. [quoted text clipped - 14 lines] > at fully charged, but will fail to start with the battery > even slightly discharged. New brushes are attached to the voltage regulator. If you put a new regulator in I would suggest you clean the surface of the armature with a fine fine. No abrasive paper please. I have checked the ambient current flow on my battery in 84 944 and it is zero milliamperes and zero microamperes with engine off.. All circuits are NOT fuse protected on this automobile. >Why not remove the alternator and take it to a specialist and be sure it is >working OK,if you have high mileage it could simply be a need for new >brushes. If he's really got a high drain that's killing the battery, that's the easiest to detect with a quick measurement. I reread his first post in light of his comment that the 100ma was the radio draw and see that the radio draw was only a small component of the drain, If "small" is 5%, then he's seeing a couple of amps! At 12 volts, that's going to get something really hot and will kill the battery in a day or two. It should be pretty easy to find. It's about what a tail light bulb would draw. SignatureT o d d P a t t i s t (Remove DONTSPAMME from address to email reply.) I agree with everything except the "easy to find" part.. =^) I can't remember the exact figure, but last time I checked I think I was drawing over an amp. Most of the lamps are fused so I don't think they are the culprits judging by my prior tests... Cheers! > >Why not remove the alternator and take it to a specialist and be sure it is > >working OK,if you have high mileage it could simply be a need for new [quoted text clipped - 13 lines] > T o d d P a t t i s t > (Remove DONTSPAMME from address to email reply.) ok, let's start over. 1. if your 944 is like most, you have a large wire and several small wires connected to battery +. Start by separating these wires and tell us which wire has the current flow through it. 2. if it is the large wire, inspect starter and solenoid if it is one of the small wires, tell us what it goes to. you can use the schematic in the manual to match against the color codes. it could be as simple as gunk on the solenoid (conductive gunk, but gunk nonetheless) also, a 1 amp drain is 12 watts - that's enough to make whatever is drawing it get hot. are you sure none of the lights are left on? or a fan motor? >I agree with everything except the "easy to find" part.. =^) > [quoted text clipped - 22 lines] >> T o d d P a t t i s t >> (Remove DONTSPAMME from address to email reply.) SignaturePosted via a free Usenet account from http://www.teranews.com Will do. Let me check these things out and report back... Finding this short has become somewhat of a personal quest... Thanks for all the help and support! > ok, let's start over. > 1. if your 944 is like most, you have a large wire and several small wires [quoted text clipped - 35 lines] > >> T o d d P a t t i s t > >> (Remove DONTSPAMME from address to email reply.) >I agree with everything except the "easy to find" part.. =^) I meant only that it was easy to verify that you have an excessively high drain, not that you could immediately find out what that drain is. I agree with the post by William Nob, next step is to find out which of the wires going to the battery has the 1+ amp draw on it. That will eliminate lots of suspects. This 12+ watt drain is almost certain to make something hot - probably hot enough to smell if you are close. SignatureT o d d P a t t i s t (Remove DONTSPAMME from address to email reply.) > I'm still trying to hunt down a short somewhere in my '84 944 that > causes the battery to go dead in a matter of a few days if I don't [quoted text clipped - 18 lines] > > Cheers! Not sure if this will help, although I am leaning like some of the others that your alternator may be going bad and not charging your battery to the fullest. When I got my 924 I was told the battery would die after a couple of days, and measured a 7 amp pull at the battery. Someone had removed the AC equipment, and tried to wire in a volt meter. They had royaly screwed up the grounds, attaching two of them to the clock, and the clock wire to the voltmeter, with the ground of the voltmeter going through the lights. I rewired it properly and the problem went away. HTH, Paul. SignatureEmail is bogus. Email to: p Sorah circle at mutual data period com(ercial) no spaces, and the usual punctuation where indicated. I think the best clue is the alternator light coming on dim or brighter. That tells you right there that the alternator cannot keep up with the demand. Either the Alternator is weak or you have a high resistance (short) somewhere pulling down the alternator. Keep this in mind. A slightly loose belt will cause the output to be reduced. Grab the pulley on the alternator and try to turn it. If you can spin the pulley with the belt attached it is to loose. The battery might never be getting a full charge. You could also have a bad shorted cell in the battery. I think you are ready for a new alternator. Anytime you see the idiot light, even if it is dim, you are discharging the battery. > > I'm still trying to hunt down a short somewhere in my '84 944 that > > causes the battery to go dead in a matter of a few days if I don't [quoted text clipped - 31 lines] > HTH, > Paul. disagree - it is common for the alt light to come on dimly - it could be indicative of a weak ground, but if the alt is charging the battery, which can be measured with a clip on ammeter, then the light doesn't mean anything. Your suggestion to check belt tension is good though - but don't overtighten either - >I think the best clue is the alternator light coming on dim or brighter. > That tells you right there that the alternator cannot keep up with the [quoted text clipped - 11 lines] > alternator. Anytime you see the idiot light, even if it is dim, you are > discharging the battery. SignaturePosted via a free Usenet account from http://www.teranews.com 100 milliamperes is one tenth of an ampere. 100 divided by 1000. That works out to one point two watt. Not much but enough to run the battery down quickly. >100 milliamperes is one tenth of an ampere. 100 divided by 1000. That >works out to one point two watt. Not much but enough to run the >battery down quickly. A typical 12 volt starter battery can deliver from 60 - 80 amp hours. At 0.1 amp, that's 600 to 800 hours - about a month. The 0.1 amp drain seems high to me, but not enough to kill the battery real quickly. He's seeing more than 10 times that, which will kill the battery in a day or two. SignatureT o d d P a t t i s t (Remove DONTSPAMME from address to email reply.) The poster of this problem has measured the drain and it is by his authority 100 milliamperes. > The poster of this problem has measured the drain and it is by his > authority 100 milliamperes. Also, the battery is being discharged in several days. Opinions regarding the magnitude of the drain measured and its effect are interesting but do not solve this guys problem. He has a short somewhere. Hope he can find it. >Also, the battery is being discharged in several days. Opinions >regarding the magnitude of the drain measured and its effect are >interesting but do not solve this guys problem. >He has a short somewhere. Hope he can find it. I hope he can find it too. Like you, I thought at first that his drain was only about 100ma, but that didn't seem enough to me to be killing his battery. It made me think that perhaps his problem was poor charging, which would match the fact that he was seeing the idiot light on the charging system. When he said he was seeing 1+ amps of drain, however, I was convinced that he does have a short. SignatureT o d d P a t t i s t (Remove DONTSPAMME from address to email reply.) No problem....snow probably? Hi Again! I finally found some free time this past weekend and was able to work on my beloved 944 for a bit. The end result is that I have some good news! I left the battery connected overnite and went to check things first thing in the morning when it was still a bit chilly outside. Everything I touched felt cool under the dash and hood until I got to the Ungo alarm box which felt a bit warm. Hmmmm. The prior owner had assured me that he had disconnected the unit many years ago and I had no reason not to believe him up till now. In any event, I traced all the wires from it and found a hot lead which I immediately disconnected. I also permanently removed the radio (the display was burnt out anyway). To make a long story short, my drain in now down to about 180mA. I also got a new battery and checked my charging system. I adjusted the alternator belt and found about 13.8v at the battery terminals with the engine running. Unfortunately, even though my 944 is currently drawing less than two tenths of an amp (a vast improvement from before), I realize that this means I still must have another short somewhere. I tried disconnecting the individual wires from the positive battery post and found the thick starter wire was okay as well as the thinner middle wire with the blue strip. The other two remaining thin wires BOTH indicated a drain of about 180mA. I guess I'm back to checking components to try and isolate this remaining problem. It's still good to know that I wouldn't kill my battery if I forget to disconnect it one nite. Just curious, since I found a drain on two separate wires at the positive battery post, does this mean I have at least two shorts? Cheers! You could disconnect the two culprit wires and see if the car still operates OK. Then reconnect them one at a time etc. at 180 ma, I wouldn't call it a "short" - you have two loads you still need to find. Look at the schematic and see what is connected to those two wires (you do have the schematic for your car, right? don't proceed without one, it will save you days of work -- at around 180 ma, it is probably some piece of electronics with a leaky capacitor in it - maybe a noise suppression circuit for the radio, or maybe there is a power amp that goes with your stereo, or ??? > Hi Again! snip > Unfortunately, even though my 944 is currently drawing less than two > tenths of an amp (a vast improvement from before), I realize that this [quoted text clipped - 12 lines] > > Cheers! SignaturePosted via a free Usenet account from http://www.teranews.com The previous owner has already shown that he connected some piece of junk to the battery. I would guess those other wires have some foolish application as well. Or could have insulation worn off wires somewhere. > To make a long story short, my drain in now down to >about 180mA. [quoted text clipped - 3 lines] > Just curious, since I found a drain on two separate wires at the >positive battery post, does this mean I have at least two shorts? Disconnect the two wires from the battery, hold them connected together, but separated from the battery, and connect the ammeter between them and the battery. If you see 360 ma, you have two loads. If you see only 180 then you have one load and the two wires both supply the same 180 ma load. SignatureT o d d P a t t i s t (Remove DONTSPAMME from address to email reply.) >The poster of this problem has measured the drain and it is by his >authority 100 milliamperes. No, he's clarified that the drain of the *radio* was 100 ma, and that disconnecting the radio changed the drain by only a small amount. He can't recall the exact amount of the total drain, but it's more than an amp. It should be a lot easier to find a 1+ amp drain than a mere 100ma. SignatureT o d d P a t t i s t (Remove DONTSPAMME from address to email reply.) |
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