Stick in the Fan

[Charlie_Iliff]

I finally got around to a "permanent" fix for my alternator. After I got the bad diodes fixed, on advice of the repair shop I wired it only as a one-wire alternator. It worked two or three times, just revving it until the regulator kicked it in and the voltage went to 14+. Then, it stopped doing that. I could get it to charge fine by touching a 12V lead to the pole that was originally wired by PT with continuous 12V from the accessories circuit. Since my guru opined that straight 12V would fry the diodes if left on without the engine running, I wired in a momentary contact button, with a neon panel light across it. The post on the alternator is the idiot light post, so I could have made it automatic with a low resistance panel light between the positive and the alternator. I couldn't find such a panel light with a quick look, and the pushbutton and neon were easily available.
So, now I start the machine and the panel light turns on. I press the button and the light goes out and the voltage meter goes to 14+. Gives me a great feeling of satisfaction whenever I do it.
But I will never know for sure how the stick in the fan caused the fried alternator, or even if it did. Nor will I know for sure if there is anything at all wrong with putting 12V constantly to that post as PT did it originally. I do not plan any controlled tests to see if I can cost myself an alternator.

 

[SnowRidge]

Alternators either have to have some inherent residual magnetism to excite them or an external excitation voltage has to be applied.

I'm not sure what the neon is doing. Neons usually require 65+ volts to fire. However, if it works, it works, and that's what counts.

New motto: Push for satisfaction! It could have all kinds of meanings.

 

[MossRoad]

The motto we're hearing around our company a lot lately is "Not the best, but good enough." Unfortunately, it makes sense when scraping for every penny. For example, you spends a hundred million dollars to make the best product and some clown spends just a million and gets something that's 90% as good and costs less than yours.... you get bragging rights but he gets the sales.

 

[J_J]

Snowridge is right about the excitation voltage. If an alternator is not a permanent magnet alternator, it has to have an exciting voltage to start generating volts and amps. This is normally done via the ignition switch. Manual operation is OK I guess unless you forget to hit the switch.

 

[Charlie_Iliff]

Alternators either have to have some inherent residual magnetism to excite them or an external excitation voltage has to be applied.

I'm not sure what the neon is doing. Neons usually require 65+ volts to fire. However, if it works, it works, and that's what counts.

New motto: Push for satisfaction! It could have all kinds of meanings.

The "neon" panel light was so designated on the package. I no nothing of its actual character except it is very high resistance, so doesn't pass through enough to excite the alternator. I put it directly across the switch, so it reminds me to push the button.

 

[Charlie_Iliff]

Snowridge is right about the excitation voltage. If an alternator is not a permanent magnet alternator, it has to have an exciting voltage to start generating volts and amps. This is normally done via the ignition switch. Manual operation is OK I guess unless you forget to hit the switch.

Correct, of course. That's why after I had excited it a few times it had enough residual magnetism to work as a one-wire, but after I left it a while there wasn't enough magnetism left to do the trick.
My alternator repair shop guy told me that it may damage the alternator to excite it with continuous 12V from the ignition circuit, if the key is left on without the engine running. With a high-watt panel light or a resistor in series, the voltage can be set to excite the alternator, but not enough current to damage anything if the key is left on with the engine stopped. I don't know any numbers, and I'm not sure if he's correct about all alternators, or if his concern is applicable to this particular Valeo, but my rig avoids the possible problem.

 

[Charlie_Iliff]

The motto we're hearing around our company a lot lately is "Not the best, but good enough." Unfortunately, it makes sense when scraping for every penny. For example, you spends a hundred million dollars to make the best product and some clown spends just a million and gets something that's 90% as good and costs less than yours.... you get bragging rights but he gets the sales.

Corrollary: "The perfect is the enemy of the good."

 

[Marks481]

With a high-watt panel light or a resistor in series, the voltage can be set to excite the alternator, but not enough current to damage anything if the key is left on with the engine stopped.

How about wiring the alternator excitation connection to the "START" position on the ignition switch? That way, excitation voltage is applied only while you are cranking the engine with the starter motor.

 

[J_J]

Charlie, Does your system have an internal regulator, or external regulator.

The IGN switch voltage goes to the regulator via the IGN terminal on the regulator, which then excites the field windings by sending the correct amount of voltage to excite the field. If the regulator doesn't have any feed back from the alternator, then I don't think it will supply any voltage to the field windings. On your setup, you need some way to vary the field voltage so as not to overcharge the battery. It seems like I had seen an old timer touch the battery voltage to the field terminal to test the alternators he was rebuilding. By doing that, he forced the alternator to put out max amps. This guy was good, he could take a bad alternator and rebuild it in about 20 min. He had a test stand with an AC motor that turned a belt to the alternator. It's hard to find those guys anymore. Most people just take it in to Autozone or Napa, and get a replacement.

 

[J_J]

How about wiring the alternator excitation connection to the "START" position on the ignition switch? That way, excitation voltage is applied only while you are cranking the engine with the starter motor.

Tim,

I believe the regulator has to have a voltage from the IGN switch at all times, meaning the on position, to energize the the regulator/alternator. The start position would only give a momentary connection, and then the alternator would lose the exciting voltage.