Lil Gypsy Posted August 30, 2009 Share Posted August 30, 2009 I went out to start my 1990 Odyssee and found the battery to be dead. I jumped it and left it running and then it died about 30 minutes later. I jumped it again and took it to my neighborhood mechanic to check it to see if it was the alternator...which after he put a meter to it ... it indicated the alternator wasn't charging the engine battery. The coach lights were working during this time. The mechanic replaced the alternator with another new one and said the same thing was happening. Has anyone else had this problem? and can you maybe give me some insight into what the problem might be. Quote Link to comment Share on other sites More sharing options...
Lil Gypsy Posted August 30, 2009 Author Share Posted August 30, 2009 I went out to start my 1990 Odyssee and found the battery to be dead. I jumped it and left it running and then it died about 30 minutes later. I jumped it again and took it to my neighborhood mechanic to check it to see if it was the alternator...which after he put a meter to it ... it indicated the alternator wasn't charging the engine battery. The coach lights were working during this time. The mechanic replaced the alternator with another new one and said the same thing was happening. Has anyone else had this problem? and can you maybe give me some insight into what the problem might be. also, as I drove it to the shop the battery light and the brake light remained on. The mechanic said that at 15 apms the alternator works fine but when it gets up to 16 is when the alternator shuts down. Any help or assistance with this would be gratefully accepted! Quote Link to comment Share on other sites More sharing options...
Bodybagger Posted August 31, 2009 Share Posted August 31, 2009 Yes I have had that problem. And nothing was wrong with my alternator. Follow the thick wire from the alternator and you will find it does not go to the battery, but rather goes to a charging splitter called a battery isolator. There are leads on this isolator for the alternator, the truck battery, and the coach battery (some have a 4th lead for the ignition). The alternator will shut off when it does not see battery voltage! What is happening is the isolator is cutting out and the alternator's open circuit protection is kicking in. Find the wire that connects the isolator to the main fuse buss next to the battery. This wire originally went to the alternator. If you disconnect it from the isolator and connect it to the alternator, the alternator will once again see battery voltage and it will charge (if everything else is working). If not, check the 80 amp fuse on the main fuse buss under the hood. Also, check the 10 amp engine fuse. If everything works as it should when the alternator is connected to the original charging wire, it means you need a new battery isolator. Shame on your mechanic! Not only did he forgo a proper diagnosis and jump right to the "replace parts til it works" technique, but instead of starting by replacing the cheapest part in the charging system and working his way up, he started with the most expensive part in the charging system and is working his way down. Quote Link to comment Share on other sites More sharing options...
Lil Gypsy Posted August 31, 2009 Author Share Posted August 31, 2009 Yes I have had that problem. And nothing was wrong with my alternator. Follow the thick wire from the alternator and you will find it does not go to the battery, but rather goes to a charging splitter called a battery isolator. There are leads on this isolator for the alternator, the truck battery, and the coach battery (some have a 4th lead for the ignition). The alternator will shut off when it does not see battery voltage! What is happening is the isolator is cutting out and the alternator's open circuit protection is kicking in. Find the wire that connects the isolator to the main fuse buss next to the battery. This wire originally went to the alternator. If you disconnect it from the isolator and connect it to the alternator, the alternator will once again see battery voltage and it will charge (if everything else is working). If not, check the 80 amp fuse on the main fuse buss under the hood. Also, check the 10 amp engine fuse. If everything works as it should when the alternator is connected to the original charging wire, it means you need a new battery isolator. Shame on your mechanic! Not only did he forgo a proper diagnosis and jump right to the "replace parts til it works" technique, but instead of starting by replacing the cheapest part in the charging system and working his way up, he started with the most expensive part in the charging system and is working his way down. Quote Link to comment Share on other sites More sharing options...
Lil Gypsy Posted August 31, 2009 Author Share Posted August 31, 2009 Thanks for the input, I really appreciate your help. Well, the alternator has been replaced along with a breaker and wire. I brought her home and as I rounded the corner the brake and battery light came back on. Before taking it in to check out the alternator, the cabin lights and all the switches on my hood ( tank levels, battery level pump and hood fan and light) were functioning properly. No I have no power to the tank level indicator or the battery indicator. The mechanic said he checked the isolator but it was fine. He tried to sell me 2 new batteries, and charged me to trouble shoot on top of the labor and the alternator. I'm soooooo frustrated. I feel assaulted and now it's taken my last bit of saving. What can I do now without it costing my first born maile child. Quote Link to comment Share on other sites More sharing options...
Bodybagger Posted August 31, 2009 Share Posted August 31, 2009 What can I do now without it costing my first born maile child. First thing's first. Checking the isolator with a diode test while sitting still doesn't mean the isolator is good. It might be getting hot and opening up the circuit. You'll need the following: 10mm socket battery charger battery hydrometer ($7.19 and you really should have one) http://www.carparts.com/OTC-PROFESSIONAL-BATTERY-HYDROMETER/GP_2010637_N__10618.car?zmam=73771597&zmas=17&zmac=100&zmap=10618-2010637 Digital multimeter. I recommend one with a clamp-on DC ammeter. Sears sells one for 50-60 bucks that will measure DC amps. Take the isolator and 2nd battery out of the equation. But before doing any of the following, disconnect your truck battery. You'll need to clean the connections anyway just to be sure. *Disconnect the large wire that is currently connected to the alternator and wrap the end with electrical tape and secure it in a safe location. *Then find the large wire that goes between main fuse buss (next to the battery) and the isolator. Disconnect the end that is currently connected to the isolator and re-connect it to the alternator. *Test for continuity between the charging post of the alternator and the positive battery cable connector. If no continuity, stop. You've found the problem. *If you have continuity, clean the battery terminals and connectors with a small wire brush or battery terminal cleaning tool. *Check the voltage of the battery. It should be 12.3 volts DC or greater. If low, charge it after you do the following maintenance. *Pop the caps and check the electrolyte gravity with a battery hydrometer. Should be 1.27 *Top off the electrolyte with distilled water if it is low. Should be just below the caps. Not filtered water, not drinking water, not Evian or Perrier, but distilled water and only distilled water. *If voltage or specific gravity was low, charge at this time. Probably overnight. *Reconnect battery leads. *Start the truck. If the battery light will not go out, check 15A engine fuse, 7.5A charge fuse, and fusible links AM1 and AM2. *Run the truck for while like this, if this fixes your problem, you have a bad isolator. One thing that you can count on though is it's probably not your alternator. If you know ohms law, and you have a DC clamp on meter, you can do this yourself. Quote Link to comment Share on other sites More sharing options...
Maineah Posted August 31, 2009 Share Posted August 31, 2009 Sounds like you need to find some one that understands what they are doing. You may or may not have a solid state isolator if it is not solid state the alternator will charge the truck battery even if the isolator is bad. If it is solid state a simple jumper wire will bypass it for test purposes. The guy told you your alternator was bad, either he needs to put your old one back on, refund your money or fix it. This is not rocket science some one that understands electrical systems should have no problem with this. He had a lot of nerve charging you to try and find out what was wrong after he sold you a part you did not need. Quote Link to comment Share on other sites More sharing options...
Tony D. Posted September 5, 2009 Share Posted September 5, 2009 Yes I have had that problem. And nothing was wrong with my alternator. Follow the thick wire from the alternator and you will find it does not go to the battery, but rather goes to a charging splitter called a battery isolator. There are leads on this isolator for the alternator, the truck battery, and the coach battery (some have a 4th lead for the ignition). The alternator will shut off when it does not see battery voltage! What is happening is the isolator is cutting out and the alternator's open circuit protection is kicking in. Find the wire that connects the isolator to the main fuse buss next to the battery. This wire originally went to the alternator. If you disconnect it from the isolator and connect it to the alternator, the alternator will once again see battery voltage and it will charge (if everything else is working). If not, check the 80 amp fuse on the main fuse buss under the hood. Also, check the 10 amp engine fuse. If everything works as it should when the alternator is connected to the original charging wire, it means you need a new battery isolator. Shame on your mechanic! Not only did he forgo a proper diagnosis and jump right to the "replace parts til it works" technique, but instead of starting by replacing the cheapest part in the charging system and working his way up, he started with the most expensive part in the charging system and is working his way down. I have also had a similiar problem with one addition. It blew the EFI fuse under my dash. I stop and had a mechanic put a meter on it and he said my alternator was defective. We changed the alternator and the light continued to flicker along with brake light staying on and blowing the fuse. Since it continued to run we kept driving and about a hundred miles down the road in West Texas in the middle of a rain storm everything begin to work proper. About 300 miles later I blew the fuse again light flickers and brake light stays on. I changed the fuse and drove on to New Orleans and back to Shreveport without any further problem. What worries me is that it may blow the fuse again at any moment. I would rather fix it than just change the fuse I am not sure if the fuse is blowing as I turn it off or when it first starts. Once the fuse blows it will not start but if it is already running and the Alt light flickers and the brake stays on it will continue to run at least in the day light. Once at night when it happened it just shut down the motor completely. Not knowing the problem that time I had it tow in and cost a big bill. Any suggestion would be welcomed. Quote Link to comment Share on other sites More sharing options...
Maineah Posted September 5, 2009 Share Posted September 5, 2009 I have also had a similiar problem with one addition. It blew the EFI fuse under my dash. I stop and had a mechanic put a meter on it and he said my alternator was defective. We changed the alternator and the light continued to flicker along with brake light staying on and blowing the fuse. Since it continued to run we kept driving and about a hundred miles down the road in West Texas in the middle of a rain storm everything begin to work proper. About 300 miles later I blew the fuse again light flickers and brake light stays on. I changed the fuse and drove on to New Orleans and back to Shreveport without any further problem. What worries me is that it may blow the fuse again at any moment. I would rather fix it than just change the fuse I am not sure if the fuse is blowing as I turn it off or when it first starts. Once the fuse blows it will not start but if it is already running and the Alt light flickers and the brake stays on it will continue to run at least in the day light. Once at night when it happened it just shut down the motor completely. Not knowing the problem that time I had it tow in and cost a big bill. Any suggestion would be welcomed. I am pretty sure the ECM fuse is linked to the exciter for the alternator. There is a wire that feeds the alternator that is energized when the key is on. It wakes up the regulator that is inside of the alternator and turns off the regulator/alternator when the key is turned off I think it is white with a black tracer it goes to the alternator terminal marked "ign". Don't assume it is the alternator causing the problem there is other wiring that is under that fuse if that wire loses power it will quit charging and that is probably why it died at night. Quote Link to comment Share on other sites More sharing options...
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