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12 volt alternator question?
There’s always been about a 10 min delay between the time I start the DD60s engine and when the 12 volt alternator comes online. Anybody know why? The 24v alternator comes online immediately.
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23 Replies
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That issue has been discussed on a great number of forums and the responses (I did not say reasons) range from bad batteries, to bad diodes, to bad regulator, to a need for higher RPM to trigger the charging.
I have a truck alternator that will not begin charging until I put it in fast idle or increase the RPM. Then it charges and maintains the charge rate as long as the engine is running. I’m not saying it is right, but as long as it charges reliably I am not going to chase the cause. Have you increased the RPM to see if that brings it on line?
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My delco SI series alternator takes more than high idle. mine will not start until about 1300 rpm.
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Hi idle has no effect. It always waits till I’m down the road a little ways then it comes online and stays online?
I changed all the belts on the engine yesterday. The only belt that looked old and/or tired was the the only belt that was a little difficult to change, the 12v alternator belt. There’s a 2 bolt bracket for a 90 degree gearbox airbag
that needs to be loosened to get the 12v alternator belt on and off.
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From the NAPA parts days it was a common question. Nothing at all to worry about according to the alternator rebuilders.
Has to do with the type of regulator which needs to be excited around 1200 RPM at which time it kicks in. Most of the questions have disappeared over time as the tech-knowledge and regulators have changed.
Our Country Coach Affinity with a C-12 had a Leece-Neville alternator which was not excited until around 1200 rpm.
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I have a question….
How do you know if the alternator is ‘alive’ or not? We have four alternators and I don’t recall a gauge on the dash for the alternator (not at the coach at the moment).
You can see that I’m in desparate need of Jeff’s class in Vonore.
Mark
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All our coaches should have a gauge somewhere for the various electrical system voltage and loads. 24 volt coaches likely use a single large alternator on all older coaches and Prevost has a dash gauge. Usually the converter adds a gauge to show house DC voltage.
The problem in giving a blanket answer to the question is there are different ways Prevost and the converters display the information so the answers are likely not only converter specific, but might also be specific to certain model years. I do not know about Mark’s question since he has multiple alternators to charge the same system(s) but I suspect there might be a tell tale light or some device to provide information that one of the alternators has failed.
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Our coach has a combination volt/amp gauge for each alternator. Pic was taken with key in the on position but the engine off
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Lonestarace,
We don’t have those gauges. I’ve noticed that they have been removed on later models. Ours must be in the center cluster, I’ll have to check it out.
Since my alternators are working fine, I’ve not really checked on the gauges. Still learning.
Mark
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Mark,
Does your coach have an annunciator light to warn of a failed alternator? Since all of your alternators have the same voltage output if one fails you just have less total amperage so voltage would not be an adequate indicator.
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Jon,
I’m away from the coach but will check on it tomorrow (Monday). I’m sure I have some type of light/warning as we have so much built into the center computer cluster.
My understanding is that we have four alternators so that we can power all four inverters while going down the road.
Mark
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But your alternators are not assigned or dedicated to any specific A/C unit, but each contributes the power necessary to keep pace with the load they impose on the batteries via the inverters.
FWIW I would crank up the generator and turn on all 4 A/C units, plus any other loads I wanted to lighten the loads imposed on the batteries and inverters and to give the generator the exrecise it needs.
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Looking at the owner’s manual, we have a ‘Battery voltage warning’ icon in the instrument cluster. It’s a picture of a battery with an exclamation point next to it. It will illuminate in the event of high/low voltage or if the 12 volt / 24 volt battery arrangement is not equalized.
In the normal instrument cluster, we have a battery icon showing the voltmeter for the 12 volt and 24 volt systems. It doesn’t mention individual alternators, just that the whole system is operating correctly.
Mark
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We have a question for Jeff then…………..
If you have 4 alternators how do you know one has quit? I cannot imagine owners have to check output with a meter.
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I *think* there is some message that the MCD displays when there is an alt. failure. I will have to see if I can find out for sure.
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Jon Wrote: “If you have 4 alternators how do you know one has quit? I cannot imagine owners have to check output with a meter.”
After the coach runs for a while and there is presumably a load on the alternators, put your hand on each one. Shouldn’t the “bad one” should be less hot than the other three?
Do the new coaches really have four alternators? That seems like quite a few. Are there four to provide the needed capacity? or for redundancy? or both?
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