Testing a Voltage Regulator

GarageTimeTV

GarageTimeTV

Garage Time TV
Quick question. (1968 850 Spider)

I think my voltage regular is bad. When I start the engine, I let it run for a second. (Note: I have to start the engine with a jumper button in the engine bay as the ignition switch won't turn the starter. It lights up a test light, but wont engage the starter) Nothing on the dash moves (Except the tach). I manually test my oil pressure switch and it does open from a cold to running, but the gauge says nothing. Same for my water temperature. Same for my fuel level, the red warning "low fuel" light is on even though its well over half full. (I have a brand new sending unit installed) I go to my manual and see that all these things are on the fuse with the voltage regulator. The thick pink wire is hot. Reads 12v on the multi meter, the other two posts read 0v.

The manual has instructions on testing it, but requires them to be at 47-53 degrees Celsius. It never gets that hot to the touch. I look at my wiring diagram and each years shows an alternator, not the generator that I have. The diagrams show a "field circuit relay" and I do not have that (probably because I have a generator, not an alternator).

So my question is, where should I start? Maybe it just needs the terminals cleaned? Can it be bench tested? Any direction is much appreciated.
 
If your battery is sitting at 12V with the engine off, something must have kept it charged. If the battery is charged and all those switches and gauges don't work, it may be something else like a wiring problem. The voltage regulator for either a generator or an alternator controls the output voltage by adjusting the current in the field winding (usually via varying the duty cycle). If you can get the engine to run, check the voltage at the generator output. If it is working, the output will likely be in the 14V - 15V range.
 
I should have clarified. The engine was off when I got that reading. I should probably do that with the engine running and report back. I keep a trickle charger on also, so that is why it is full.
 
Thank you! I might as well do the same. Would you mind showing how yours is in the car? Since the factory has 3 terminals and this one has two, I’m assuming the thick pink wire is not needed.
 
Here is mine in the car. On the alternator cars, it appears that there are only two wires.
F5884D3E-DA4F-4A8C-A5B3-78C0711795E5.png
 
The regulator for an alternator has 2 terminals and for a generator it has 3 terminals so that Lazorlite regulator won't work. An alternator needs a relay to cut out the field coil circuit when the engine isn't running (to prevent discharging the battery). A generator does not have a relay in the circuit. A new 3-wire regulator is something like $150 if you were to replace the old one, but it may not even be a regulator problem. First thing I would try is opening up the regulator and cleaning the relay contact surfaces. Bench testing a regulator is not straightforward.

The issue may not be the regulator and might be the generator. I'd take the generator apart and clean the armature and brush surfaces. Could also be a bad connection at a terminal(s) somewhere. I'd try cleaning all contact surfaces in the positive battery, generator, regulator & negative chassis connections. Crimp connections on ground and positive cables can sometimes also eventually go bad.

What is the battery voltage when engine is off? A fully charged battery should be around 12.7 volts. 12.0 volts would be about 50% discharged. What does the voltage read when you rev up the engine? The generator needs to put out 14+ volts to charge a lead-acid battery. If the battery is indeed down to 50%, the starter solenoid may not work. But if the battery is near or at fully charged and the solenoid won't work, it could be dirty contact surfaces inside and you can take it apart and clean the contacts. If you have a battery charger, can you get the batter up to 100% charge and have it stay at 12.7 volts? Maybe the battery is no good? A slipping fan belt can cause a generator to not charge properly but you'd likely notice overheating (unless temp. gauge not working properly). You definitely don't want an overheated engine.

If gauges also aren't working, that suggests a bad ground somewhere, especially if the battery isn't charging up properly. You could try measuring the voltage at pos. connections under the dash and see if it reads the same at the battery. Fixing electrical problems can be one of the hardest things to do because you can't see where the electrons are going. :(
 
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There’s no relay in the alternator cct of my x1/9 or Alfasud, at all. Also 2.2v / cell is more typical of a good battery IE <13.2v
D10B36A2-2B47-421F-980C-5545F62239EB.png
 
NEG said:
There’s no relay in the alternator cct of my x1/9 or Alfasud, at all. Also 2.2v / cell is more typical of a good battery IE <13.2vView attachment 45424
Click to expand...
Early X’s did have an external regulator though no field relays or relays to light the alternator light. Early 124s had a very similar charging system to the system on an 850.
 
850EV said:
Quick question. (1968 850 Spider)

I think my voltage regular is bad. When I start the engine, I let it run for a second. (Note: I have to start the engine with a jumper button in the engine bay as the ignition switch won't turn the starter. It lights up a test light, but wont engage the starter) Nothing on the dash moves (Except the tach). I manually test my oil pressure switch and it does open from a cold to running, but the gauge says nothing. Same for my water temperature. Same for my fuel level, the red warning "low fuel" light is on even though its well over half full. (I have a brand new sending unit installed) I go to my manual and see that all these things are on the fuse with the voltage regulator. The thick pink wire is hot. Reads 12v on the multi meter, the other two posts read 0v.

The manual has instructions on testing it, but requires them to be at 47-53 degrees Celsius. It never gets that hot to the touch. I look at my wiring diagram and each years shows an alternator, not the generator that I have. The diagrams show a "field circuit relay" and I do not have that (probably because I have a generator, not an alternator).

So my question is, where should I start? Maybe it just needs the terminals cleaned? Can it be bench tested? Any direction is much appreciated.
Click to expand...
did you resolve your regulator issues if not let me know i might be able to help you acquire one for a good price depending of Where your located
 
Peppi said:
did you resolve your regulator issues if not let me know i might be able to help you acquire one for a good price depending of Where your located
Click to expand...
Thanks! I haven't had a chance to get back to the car yet to test it. My house was flooded in the Texas freeze so I am away from the house during the rebuild. I will be checking tomorrow when I get there and PM you if I needed it.
 
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