More Alternator woes

Topic: More Alternator woes (Read 2009 times) previous topic - next topic

More Alternator woes

August 09, 2019, 10:12:37 pm

As my coach seems to like stressing me out. It of course decided to continue with almost no voltage from my new (not Reman) Delco-Remy 28si 180amp alternator. As this alternator doesn't need an excite wire. I terminated that one and insulated it. I left the old diode isolator in for now and will install the sterling zero loss later. I hooked up the start batt. Sense wire to the S terminal which is next to the Pos output. That showed battery Voltage like it should.

Upon starting the coach, I went to high idle (1000 RPM) and saw low volts at the gauge. Then I measured voltage at the center terminal of the isolator. 1.7V. Measured the voltage at the pos output to ground. It was 1.7V.

To summarize:
Batt voltage, 12V
Sense wire at Alt, 12V
Alt input wire at isolator, 1.7V
Alt. positive output terminal, 1.7V

Bad alternator?

Re: More Alternator woes

Reply #1 – August 09, 2019, 10:25:02 pm

Bad alternator.

Re: More Alternator woes

Reply #2 – August 09, 2019, 10:35:19 pm

Quote from: Tim – August 09, 2019, 10:25:02 pm

Bad alternator.

I hope so as that's an easy swap.
Need to find a shop that can test one. NAPA here is useless as it's not one of theirs so the computer has no data for it. Geez. You think they could just spin it up and measure voltage.

Re: More Alternator woes

Reply #3 – August 09, 2019, 10:39:25 pm

Had the same hassle at Auto Zone,Installed a 160 amp 28si 2 years ago along with a new isolator and everything new on the
mounting plate,haven't had a problem,charges much better at low rpm.

Re: More Alternator woes

Reply #4 – August 09, 2019, 10:50:07 pm

Well against my better judgement. I decided to save a few bucks and went big box truck parts place. Should have spent the coin and stayed local. A local truck shop that does my oily work has the 28si 160amp. I think I will go with that.

Re: More Alternator woes

Reply #5 – August 09, 2019, 10:55:26 pm

Nothing wrong with the alternator. Delco alternators won't work with a standard diode isolator, they need +12 volts on the B+ post to initialize the regulator chip. Either install a diode isolator with an ignition excite post, or wait until you get your Sterling. Connect the excite wire to either one, your Delco should then work fine.

Note: Do not connect ignition excite wire directly to a Delco alternator.

Re: More Alternator woes

Reply #6 – August 09, 2019, 11:00:24 pm

It will work fine with your Sterling as Peter says.

Re: More Alternator woes

Reply #7 – August 09, 2019, 11:20:30 pm

Quote from: prfleming – August 09, 2019, 10:55:26 pm

Nothing wrong with the alternator. Delco alternators won't work with a standard diode isolator, they need +12 volts on the B+ post to initialize the regulator chip. Either install a diode isolator with an ignition excite post, or wait until you get your Sterling. Connect the excite wire to either one, your Delco should then work fine.

Note: Do not connect ignition excite wire directly to a Delco alternator.

What? Wait now I'm totally confused.
There is a spot on the alt. for an ignition wire.

Re: More Alternator woes

Reply #8 – August 09, 2019, 11:32:45 pm

Jerry, you're not the first one...contrary to what you may have heard, Delcos are not a drop-in replacement alternator in a 2 battery isolator system. A diode isolator with excite post or the Sterling isolator with excite post will work with a Delco alternator to provide the B+ voltage needed at startup.

The "I" post is for indicator lamp. Connecting excite to this will permanently damage the alternator.

Re: More Alternator woes

Reply #9 – August 09, 2019, 11:36:52 pm

Hook up only the sense wire to the S post, nothing to the I or R posts, in addition to the big ground and the B+ output cable.

Re: More Alternator woes

Reply #10 – August 09, 2019, 11:43:47 pm

Quote from: Roger & Susan in Home2 – August 09, 2019, 11:36:52 pm

Hook up only the sense wire to the S post, nothing to the I or R posts, in addition to the big ground and the B+ output cable.

That's the way I have it hooked up now.

Re: More Alternator woes

Reply #11 – August 09, 2019, 11:45:37 pm

OK, So as i'm looking at the old diode isolator. The main thing that confuses me is that at both outputs. There are smaller wires on those terminal along with the big battery cables. What are those?

Re: More Alternator woes

Reply #12 – August 10, 2019, 12:04:39 am

This will get you going until you get the Sterling.

Delco compatible isolator

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Re: More Alternator woes

Reply #13 – August 10, 2019, 12:40:10 am

Quote from: prfleming – August 10, 2019, 12:04:39 am

This will get you going until you get the Sterling.

Delco compatible isolator

I already have the sterling. I was just going to use the old iso until it isn't 100 degrees out. As in this fall when we get ready to go south. However, As this issue has come up. I'm going to install the Sterling in the morning. It just won't be a pretty mounting.

The part I was confused about were the two small wires coming off of each battery bank output on the old isolator. I would think the one on the start batteries is the sense wire. But the small wire on the house bank is?

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Re: More Alternator woes

Reply #14 – August 10, 2019, 03:40:32 am

OK. After reading and re-reading Rogers old post on his switch to the Delco/Sterling combo.

I terminate the old sense wire, Then run a new sense wire from the Delco S post to the Sterling Sense post.

Then I need to run a wire from the old FT excite wire to the Ign wire on the Sterling.

All the Battery cables from the old Diode iso are just pushed over to the new Sterling. I take it the two small wires that are confusing me on the old diode iso at the Battery cables are the two Solenoid trigger wires?
And yes it is a stupid question. Do those small wires also just get swapped over just as they are on the old Iso? I would think so.

Re: More Alternator woes

Reply #15 – August 10, 2019, 10:26:56 am

Hi Jerry,
It is pretty straight forward. The Sterling sense to the Delco S post is right. The Sterling ign post needs an ignition powered wire to turn on so the excite wire will work. Often times these old wires have corroded connectors. I just ran new wires.

As built (on my coach) there were no other wires connected to the three isolator posts other than the alternator to the center post and a start post cable to the start battery side if the boost solenoid and the house (B2 I think they called it on the Sterling) post cable to the opposite side of the boost solenoid. Other wires may have been added over time. My Progressive EMS is powered off the house post.

There are many now with an added solar charger, battery charger and more stuff. When you make changes to your coach keep good notes, draw a new wiring diagram and save it and probably most important label the wires. Lots of variations on these but however label them.
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There was a mislabeled drawing in my old post but it is too old to edit.

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Re: More Alternator woes

Reply #16 – August 10, 2019, 11:21:38 am

Thanks Roger. I will look at the wiring chart before I get started. Not supposed to be as hot today & Sunday. So that will help. 100 degrees like it has been and parked on a sticker infested patch of dead grass with no shade is not a good motivator.

Thought a new efficient iso would be a nice option, Almost didn't buy it. I had ZERO idea that a new iso was mandatory with a Delco.

Guess I missed that memo.

Re: More Alternator woes

Reply #17 – August 10, 2019, 11:25:53 am

Peter was also a big help when I installed mine,good to see your still out there.

Re: More Alternator woes

Reply #18 – August 10, 2019, 02:02:46 pm

Quote from: prfleming – August 09, 2019, 11:32:45 pm

The "I" post is for indicator lamp. Connecting excite to this will permanently damage the alternator.

I only work on old stuff and only for my pleasure, but Delco used to use the "generator" light to provide the exciter voltage to the alternator. Bad light bulb means no alternator output.

Re: More Alternator woes

Reply #19 – August 10, 2019, 07:22:29 pm

Quote from: Old Toolmaker – August 10, 2019, 02:02:46 pm

I only work on old stuff and only for my pleasure, but Delco used to use the "generator" light to provide the exciter voltage to the alternator. Bad light bulb means no alternator output.

You're right I think the old Delcos (before digital regulators) worked this way, the new Delcos have output with nothing connected to the "I" post.

Re: More Alternator woes

Reply #20 – August 10, 2019, 07:31:06 pm

Quote from: prfleming – August 10, 2019, 07:22:29 pm

You're right I think the old Delcos (before Sense technology) worked this way, the new Delcos have output with nothing connected to the "I" post.

On the flat bottoms we put a resister between the two male spade connectors to be able to just use one wire. No idiot lights on the boats.

Re: More Alternator woes

Reply #21 – August 10, 2019, 08:03:52 pm

Maybe the 2 small wires at the isolator go to a battery maintainer for the chassis battery, like a battery tender or heart echo charger.

Re: More Alternator woes

Reply #22 – August 10, 2019, 09:11:42 pm

Quote from: red tractor – August 10, 2019, 08:03:52 pm

Maybe the 2 small wires at the isolator go to a battery maintainer for the chassis battery, like a battery tender or heart echo charger.

I did see one wire on the wiring diagram that goes to a solenoid on the start battery side. I have the standard Heart interface 2500 and the Xantrex panel on the china cupboard. The interface doesn't have a trickle charger.

When I go back to the coach tomorrow. I will pull that second wire and see what changes. I suspect that perhaps it is the second Battery voltage readout on the panel in the coach? I didn't look at that section of the diagram. However if it was factory. It certainly should have been noted on the main wiring page that shows the Isolator.

Didn't get much done today though. Had a sleepless night. Then got out later than I wanted. Got out of the house without having drank any water. 2 hours later I was feeling the sun and unwell and so called it a day.

Re: More Alternator woes

Reply #23 – August 11, 2019, 04:30:35 am

Quote from: bigdog – August 10, 2019, 11:21:38 am

Guess I missed that memo.

Here is the Delco bulletin on using the 24SI with isolator, this also applies to the 28SI, 40SI.

Re: More Alternator woes

Reply #24 – August 11, 2019, 09:52:53 am

Quote from: bigdog – August 09, 2019, 10:12:37 pm

Upon starting the coach, I went to high idle (1000 RPM) and saw low volts at the gauge. Then I measured voltage at the center terminal of the isolator. 1.7V. Measured the voltage at the pos output to ground. It was 1.7V.

To summarize:
Batt voltage, 12V
Sense wire at Alt, 12V
Alt input wire at isolator, 1.7V
Alt. positive output terminal, 1.7V

Bad alternator?

"I think" that you can use your still good diode isolator by adding a wire to terminal #1 from the ignition switch through one of the listed options, a 5W Diode, a resistor or a 3 candle power bulb.
Tell me why I'm wrong.

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