Charging issues.

[Industrial Toys]

If the pickup is before the voltage regulator, I don't see how you can get loss of signal.

Is there an adjustment on the tach to calibrate the tach for given pulley size/speed?

 

[Winmac]

An oem tach may not have an adjustment but most aftermarket will have a calibration pot, or be programable.

If the alternator dose not excite the field windings there is no signal for tach.

We encounter a similar issue as the op when the gauge clusters were upgraded to led bulbs, the led did not provide enough current to excite the field but blipping the throttle would self excite the alternator. We had to install a resistor kit in the harness to overcome the issue.

 

[Steave]

Don't know anything about them but reading about the tach itself (which is pricey) they do have a calibrator in them and the tach actually operates off a built in step motor that receives the AC signal.

Lot of old ford gassers around that have been changed to an alternator now have no tach. Might be a good fix for them. Mine still has the generator and tach as I depend on my tach when operating any of my junk.

 

[Steave]

An oem tach may not have an adjustment but most aftermarket will have a calibration pot, or be programable.

If the alternator dose not excite the field windings there is no signal for tach.

We encounter a similar issue as the op when the gauge clusters were upgraded to led bulbs, the led did not provide enough current to excite the field but blipping the throttle would self excite the alternator. We had to install a resistor kit in the harness to overcome the issue.

Does the tach just have the one wire from the alternator and then grounded? Just curious. The aftermarket ones I looked at had a wiring harness with it looked like several wires in it.?

 

[Industrial Toys]

Could one not just turn on a light to provide some load?

 

[Steave]

Could one not just turn on a light to provide some load?

No the load has to be in series with the terminal that goes to the indicator bulb.

 

[Winmac]

Does the tach just have the one wire from the alternator and then grounded? Just curious. The aftermarket ones I looked at had a wiring harness with it looked like several wires in it.?

There are several connections, a switched power supply, ground, dash light and there are extra connectors because they are designed to accept three different signal types, alternator, tacho generator or flywheel magnetic pick up.

 

[Steave]

Oh, so the tach can be used under several applications. I noticed some of them are pricey but I suppose they would be since you'd be able to calibrate them. If I ever had to change my ford to an alternator would check in on this type of Tach but finding a place to mount a new Tach might be fun.

Well we've managed to keep this post alive for the OP until he posts back after the weekend. I'm sure curious now what he finds. For me thanks for the info and I'm sure some of it will help the OP with his troubles.

 

[kc5dlo]

Figured out most of the issues. The warning light for the alternator was burnt out. A new bulb did not fix it. In fact after changing all the bulbs, the oil pressure warning light that was working before was no longer working. Had to fiddle with the bulb holders to get them to make contact. Ordered half a dozen new holders online as the local auto parts only had 2. The alternator warning light does work correctly now and the tach instantly fires to life now when started at idle and no revving required to start charging.

I still think the new alternator is probably good. Like someone mentioned, the diodes in the old alternator were probably leaking enough to self excite it. Are the diodes part of the regulator? If so, I might swap in the new alternator and tag the old one that it needs a new regulator and hang on the wall.

Oh, and someone asked if the new one was the same as the old one. The castings looked the same and connections were the same.

Thanks for the help and insight everyone!!
Steve

 

[Winmac]

I've not had a chance to take apart a Bosch alt but typically dieodes are not part of the regulator, I believe with the Bosch they are soldered in place and not easily changed.