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Over charging with new 50 DN alternator
Wondering if anyone has had this issue.
Had new 4DL batteries ( Thanks Tom) and new 50 DN Alternator installed at Mira Loma Prevost in March 2022 on the way home my secondary battery light was flashing periodically.
When I got home checked voltage at 50DN alternator and regulator output 29 – 30 volts readings on inverter gauges inside reading same. Adjusted regulator made no difference. Installed new regulator same readings.
I live in Abbotsford B.C. so not feasible to go back to have them look at.
Any thoughts
Thanks
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8 Replies
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First, get a decent quality volt/ohm meter or multi-tester. Fluke is good but there are others.
Then whenever measuring electrical values rely in the tester. I have two identical gauges in my coach measuring alternator output and they are different by one volt. That does not sound like much but it is.
The Prevost service manual for our coaches provides the proper voltage value to a correctly adjusted regulator. It is around 27 volts give or take a few tenths (going by memory) and at the specified voltage level it will not damage batteries, house or chassis.
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Randy, a call to Mira Loma may be in order to find out if they adjusted the regulator after the 50DN and battery change. Those voltages won’t hurt your Lifelines in the short term, but the alternator needs to be adjusted for sure. As Jon mentioned, did you check the battery voltage with a good meter at the batteries while the bus was running?
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Mira Loma did not adjust regulator I did when I got home did not make any difference. Called Scott at Mira Loma suggested to install new regulator I installed new regulator made no difference tried adjusting new one no change. House batteries at low idle all read 14.8 – 15 Vanner house battery equalizer reading 29 30 . Techlink reading inside 29 -30 Inverter gauges inside 29 30
I have 2 Mac tool meters both same readings there were no issues prior to DN 50 and battery install
Prior voltage ranged 26.8 – 27.8 give or take a bit I will give Scott a call again I think they will be scratching there heads
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Randy, the actual voltage you stated will cook the batteries. It has to be closer to the 27 volts I mentioned and what you said it should be.
I agree if the voltage regulator cannot be adjusted it needs to be replaced, but what concerns me is you said even a new one cannot be adjusted. I’m not a believer in coincidences.
The regulator uses the field wire to energize the field and as the voltage is met it cycles the field wire on and off to maintain the set voltage. It is that constant on-off that limits the output voltage of the alternator The fact that the voltage is in the range you mention says it is cycling on-off as intended, but not as needed. If it maintained a constant voltage you would have runaway voltage, and if it did not provide any voltage to the field wire the alternator would not charge the batteries.
It sure sounds like a bad or non-adjustable regulator but it bothers me that two regulators fail to function as they should.
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The strange thing is that voltage was fine before new alternator and batteries installed Im thinking faulty alternator putting to much voltage out. Will call Scott next week.
Thanks for the input
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Recently I bought a New Old Stock Delco Remy 1118447 VR off ebay to carry as a spare. When I got it tried it to see if it worked. It didn’t. Once I started engine I didn’t see a rise or drop in voltage it just stayed put at about 25v, which is what it was before starting the engine. I tried to adjust it, put it just stayed at 25v. Installed my original VR, started the engine, and it jumped up to 28v where I have it adjusted to be. I let the seller know and was immediately given a refund.
My ole 24v 50DN is still good. I hope this gives you a clue?
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An alternator is a stupid device. If there was no voltage regulation you would see output voltages high enough to do substantial damage to your electrical system. Voltages would be well in excess of what you are seeing, and which likely will only damage your batteries.
Before you poke a finger at the 50DN you can quickly determine if the regulator is functioning to an extent.
Disconnect the field wire from the alternator. Connect a jumper at the alternator but leave the other end not connected to anything. Start the bus and measure voltage, which should be exactly the same voltage as the batteries with the engine off. Then contact the jumper to the positive post on the batteries (the post that corresponds to the normal output voltage of the coach. Some 50DN’s were set up for 12 volts, some for 24. Whatever yours is that is the post that corresponds to the 50DN.
Watch the voltage rise, but disconnect the wire from the battery as soon as you see it exceed the voltage you now see from the 50DN. The voltages you describe are too high to be tolerated, but do not approach the voltage level that can do serious damage.
If the unregulated voltage in your test does not exceed what you now see it is a good indication the regulator is no good, and that the 50DN needs a regulator that works.
On a 24V 50DN supplying unregulated field power the 50DN output can quickly hit and exceed as much as 33 volts.
2005 XL Thompson Coach
Rarely tow anything behind us.
Sold: 1993 Liberty that we loved for 12 years. -
What is your coach number? To many variations in how wiring was done in Marathon coaches from year to year. Here is diagram might help..
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