My original Hitachi 35 amp alternator on my 2qm15 finally died. A local alternator shop couldn't repair it so I purchased a remanufactured Hitachi 35 amp. This one has the (B) battery (E) earth and a (T) connector. From the archives I read that the vertical connector is for the charge light on the panel and the horizontal is for a 12v to the alternator for the regulator. My question is should this 12v come off the ignition switch ? I assume the old style alternator got power for the regulator from the (B) connection since it only had three connections. Kevin
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Believe that you are correct.
The 'T' connection is the exciter voltage. I have the detail on the boat and am headed there now. If only I can remember!
The 'T' connection is the exciter voltage. I have the detail on the boat and am headed there now. If only I can remember!
More info.
In front of me is a Hunter wiring diagram from a boat with the Hitachi 55Amp alternator. I bought a 55-A to replace my 35-A. The alternator posts are 'E'-ground, 'B'-battery, 'L'-lamp, and 'R'-??. The 'R' post is the one closest to the edge of the alternator, the one we are calling the 'T' connection. The diagram shows that wire going to the tachometer AND to a pushbutton for momentary 12 volts when starting. If you have a fax I can send you the diagram. I thought I had a scanned copy but cannot find it. My used alternator came with the plugs and short pieces of wire that I can splice onto. Right now it is sitting in the bottom of a locker awaiting the end of sailing season.
In front of me is a Hunter wiring diagram from a boat with the Hitachi 55Amp alternator. I bought a 55-A to replace my 35-A. The alternator posts are 'E'-ground, 'B'-battery, 'L'-lamp, and 'R'-??. The 'R' post is the one closest to the edge of the alternator, the one we are calling the 'T' connection. The diagram shows that wire going to the tachometer AND to a pushbutton for momentary 12 volts when starting. If you have a fax I can send you the diagram. I thought I had a scanned copy but cannot find it. My used alternator came with the plugs and short pieces of wire that I can splice onto. Right now it is sitting in the bottom of a locker awaiting the end of sailing season.
Thanks Ed
Thanks for the info Ed. I also did some research and am pretty sure that the top of the (T) connector is for voltage sensing and should run to the battery source so the internal regulator can adjust current to the field. My old alternator didnt have this .I guess it got its voltage sensing from the light wire. Kevin
Thanks for the info Ed. I also did some research and am pretty sure that the top of the (T) connector is for voltage sensing and should run to the battery source so the internal regulator can adjust current to the field. My old alternator didnt have this .I guess it got its voltage sensing from the light wire. Kevin
Hitachi internally regulated alternator
I did the same job as you are describing last year. I had to go through a battery to find out you absolutely need wiring on BOTH of those connections you are describing as a T. You can't get the alternator to begin charging without one of them and it won't regulate to 14.5v without the other one. The one that turns the alternator on can be the neg. wire from the "charge" lamp. After switching the alternator on this circuit is opened internal to the alternator and the lamp goes out. The other is the "sense" wire which it needs to regulate the voltage to under 14.6 volts. As I found, the 16v it maxes out at without this wire connected will boil/kill/make cheese of a battery over time. I was told by the shop where I bought the alternator that this "sense" terninal could be permanently wired to positive, but I ran it through my ignition switch anyway. I was suspect of leaving the sense wire powered permanently after the bad advice they gave me that lead me to leaving the sense wire off completely. I'd like to hear from any "experts" on this because I don't like the idea of the extra connections and contact point in the "sense" circuit I have that may not be necessary. Sorry, I didn't write down which one was which. Trial and error was my method. Take the charge light wire and hook it up to one of them, leave the other one empty. Start the engine and check the voltage. If it's on the wrong one, the voltage will stay at battery voltage, if it's on the right one you'll see over 15 volts. Get it on the right one and then hook up the "sense" wire to the other one. Start the motor and read voltage and you should see 14-14.6 volts. BTW, after installing the alternator, I did some reading and most people advise against these internally regulated alternators in boats, I forget why.
I did the same job as you are describing last year. I had to go through a battery to find out you absolutely need wiring on BOTH of those connections you are describing as a T. You can't get the alternator to begin charging without one of them and it won't regulate to 14.5v without the other one. The one that turns the alternator on can be the neg. wire from the "charge" lamp. After switching the alternator on this circuit is opened internal to the alternator and the lamp goes out. The other is the "sense" wire which it needs to regulate the voltage to under 14.6 volts. As I found, the 16v it maxes out at without this wire connected will boil/kill/make cheese of a battery over time. I was told by the shop where I bought the alternator that this "sense" terninal could be permanently wired to positive, but I ran it through my ignition switch anyway. I was suspect of leaving the sense wire powered permanently after the bad advice they gave me that lead me to leaving the sense wire off completely. I'd like to hear from any "experts" on this because I don't like the idea of the extra connections and contact point in the "sense" circuit I have that may not be necessary. Sorry, I didn't write down which one was which. Trial and error was my method. Take the charge light wire and hook it up to one of them, leave the other one empty. Start the engine and check the voltage. If it's on the wrong one, the voltage will stay at battery voltage, if it's on the right one you'll see over 15 volts. Get it on the right one and then hook up the "sense" wire to the other one. Start the motor and read voltage and you should see 14-14.6 volts. BTW, after installing the alternator, I did some reading and most people advise against these internally regulated alternators in boats, I forget why.
To Jim S.
You are absolutly correct. The top of the "T" connection should go to the batt for sensing. I read up on this quite a bit . The internal regulator draws very nominal current so you can go to a batt terminal if you like. But with multible batteries I think its better to go to a hot terminal which represents the selected batteries so you are sensing the batteries that you are charging. Some alternators wont put out any voltage unless there is power to the regulator. Aparently the Hitachies we have put out max voltage without sensing . Mine put out close to 16 volts with no sensing. 14.2 as soon as I put power to the regulator. Thanks for the reply. Kevin
You are absolutly correct. The top of the "T" connection should go to the batt for sensing. I read up on this quite a bit . The internal regulator draws very nominal current so you can go to a batt terminal if you like. But with multible batteries I think its better to go to a hot terminal which represents the selected batteries so you are sensing the batteries that you are charging. Some alternators wont put out any voltage unless there is power to the regulator. Aparently the Hitachies we have put out max voltage without sensing . Mine put out close to 16 volts with no sensing. 14.2 as soon as I put power to the regulator. Thanks for the reply. Kevin
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