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I just replaced my alternator because my amp gage was showing discharge when I turned on the headlights. My new alternator is doing the same thing. It shows a discharge when the lights are engaged. I have a new battery and a somewhat new external voltage regulator. The alternator is only showing a little over 12 volts when running, and I would think it should show around 14 volts. When I turn the light on, the voltage drops to 11 volts. I could use some advise please. I have a 1968 TR-250. Nose wants to know what to try next.
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TR5/TR250 amp gage shows discharge when lights are on
- Thread starter Nose
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What kind of alternator? Most alternator do not have a regulator because they are internally regulated.
David
This is a sketch of my wiring diagram on my TR3A. The alternator is a 3 wire alternator with 1 wire going from the No. 2 post to the alternator output. The wire from the No.1 post goes to the ignition switch via the warning light. If that bulb is blown it will not charge.
David
Madflyer
Jedi Knight
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Question? One - did you replace with LUCAS OEM ? When I had my 250 to many years ago ( 1970 ) auto parts houses sold most all elect. When my Alt failed they said buy both or no warranty. Out put is low you are looking for 13 1/2 volts. Quick note on how it works. our cars are 12 volt DC your Alt puts out Alternating volts pos & neg .The reg. diode bridge blocks neg volts and because Alt send pulses it goes to two diodes this makes for solid DC volts. If one diode is bad you get low voltage because you only get half cycle to battery. If you wish to stay OEM replace Reg before you damage Alt. As OEM is only 43 AMP's you may look into a bigger Alt. at 63 Amps for ex lights ,fans Radio system. They bolt right up plugs can match and you can replace them from any auto parts houses for less that LUCAS and REG is built in. Madflyer
Got_All_4
Luke Skywalker
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Guess I was jinx reading and replying to your post. Couple of days later my TR250 did the same thing. Power at the exciter wire all other connections were clean. Took it off and went to the parts store to test it and it was junk. Now when I rebuilt the car I did an up grade to 55amps and a Bosch internal regulator alternator. I used the Moss conversion chart to make my wiring crossovers however to keep some original appearance I used a bad voltage regulator, cut it open and made my wire jumping in there. Just ordered replacement alternator from Rock Auto tonight.
Talking to a mechanic about it he thinks I should have upgrade the charging wire or add another wire to be able to carry the extra current. I didn't think about it but over the years I added H4 headlights and Lucas Re-pops driving lights and I could have cooked the alt with the original wires being too small. I will probably add a extra wire to the voltage gauge and one larger wire from the gauge to the starter solenoid.
Talking to a mechanic about it he thinks I should have upgrade the charging wire or add another wire to be able to carry the extra current. I didn't think about it but over the years I added H4 headlights and Lucas Re-pops driving lights and I could have cooked the alt with the original wires being too small. I will probably add a extra wire to the voltage gauge and one larger wire from the gauge to the starter solenoid.
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What size wiring are you using?
If the wiring to the alternator is too small, it won't damage the alternator but it might damage the wiring. Maybe not even that. My greatest concern would be the drop in voltage between the alternator and the rest of the electrical system. Per my handbook, a 3' run of #14 will have a drop of about half a volt at 55 amps (0.0026 ohms per foot). Of course, most of the time, the alternator will be putting out much less than that.
I think I'd use #10 or, if that's too much trouble to work with, #12 for a 55-amp alternator. Stranded, of course.
If the wiring to the alternator is too small, it won't damage the alternator but it might damage the wiring. Maybe not even that. My greatest concern would be the drop in voltage between the alternator and the rest of the electrical system. Per my handbook, a 3' run of #14 will have a drop of about half a volt at 55 amps (0.0026 ohms per foot). Of course, most of the time, the alternator will be putting out much less than that.
I think I'd use #10 or, if that's too much trouble to work with, #12 for a 55-amp alternator. Stranded, of course.
I just replaced my voltage regulator, and have a new alternator, and had to switch some of the wires on the voltage regulator harness because the F and - on the new volt. reg. are not in the same order as my old Tr- 250 harness plug. I started it up and checked the voltage from the B+ and + terminals and they showed a little over 12 volts. I checked the F terminal ( which I assume is the terminal that charges the battery) only showed .56 volts. I just don't get it. When I turn my lights on my amp gage shows discharge and my battery volts drops below 12v. Help please if you can
charleyf
Luke Skywalker
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I have been waiting for somebody to either ask at what RPM you are getting your electrical measurements from or for you to say what RPM you are using as your base. I would guess that you should have at least 1500 RPM to give you the reasonable voltage from your alternator.
I had the alternator tested and it's pulling 14.5 volts. I have a new voltage regulator. Could my amp gauge be the problem. The heavy gauge wire from the alternator runs directly to the amp gauge, and then from the amp gauge to the starter solenoid, and the battery cable connects to the same terminal on the solenoid. Is it possible that the issue is the amp gauge.?????
TexasKnucklehead
Jedi Knight
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It is highly unlikely the issue is with the ammeter.
As you should know, the TR250 uses an alternator with an external regulator. Since you stated the alternator is putting out over 14 volts, I assume you had it tested. When they tested it, they must have also used an appropriate external regulator that allowed the alternator to produce the appropriate output. They may also be able to test your regulator by attaching both your regulator and your alternator at the same time, and spinning the alternator with a 12 volt source to excite the system. Then you could be sure both those units are functioning as expected.
The connections (wires and terminals) between the alternator and regulator are critical to the operation of both. The alternator relies on the regulator to control the field (F input) of the alternator which in turn affects the output of the alternator. Any addition resistance in those connections will effect the entire system. This is the reason modern alternators have the regulator built in to the alternator -not to be confused with the 3-phase diode (6 diodes) bridge which is internal to the alternator used to convert the AC to DC. Also, the regulator is designed specifically for the alternator and substitutions of either may effect the output.
I would carefully check the wires and connections between the alternator and the regulator. Be sure the regulator is connected properly as well as grounded well.
Good luck, be careful and let us know what you find.
Jer
As you should know, the TR250 uses an alternator with an external regulator. Since you stated the alternator is putting out over 14 volts, I assume you had it tested. When they tested it, they must have also used an appropriate external regulator that allowed the alternator to produce the appropriate output. They may also be able to test your regulator by attaching both your regulator and your alternator at the same time, and spinning the alternator with a 12 volt source to excite the system. Then you could be sure both those units are functioning as expected.
The connections (wires and terminals) between the alternator and regulator are critical to the operation of both. The alternator relies on the regulator to control the field (F input) of the alternator which in turn affects the output of the alternator. Any addition resistance in those connections will effect the entire system. This is the reason modern alternators have the regulator built in to the alternator -not to be confused with the 3-phase diode (6 diodes) bridge which is internal to the alternator used to convert the AC to DC. Also, the regulator is designed specifically for the alternator and substitutions of either may effect the output.
I would carefully check the wires and connections between the alternator and the regulator. Be sure the regulator is connected properly as well as grounded well.
Good luck, be careful and let us know what you find.
Jer
I did have to change several wires coming out of the alternator to the regulator., the negative and the F terminals are switched on the new voltage regulators. I will take your advise and have my (even though it's new) voltage regulator checked with the alternator before I try anything else. I have already checked the voltage at the regulator, the battery and the solenoid, and they all have the same reading with the engine running, a little over 12volts...the regulator is not sending the signal to the alternator to charge.