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Topic: 1991 U300-- bought it! (Read 9365 times) previous topic - next topic

Re: 1991 U300-- bought it!

Reply #140
My sense wire came from the fuel run solonoid  . About 12 in from the alt.

Re: 1991 U300-- bought it!

Reply #141
My sense wire came from the fuel run solonoid  . About 12 in from the alt.

I would probably choose a location less "distant" from the chassis  battery-- you really want it to accurately telegraph voltage.  If it has run through the ignition circuit up front and back to the engine, it may certainly be adequate to hold open the run solenoid, but may be several tenths of a volt lower than actual battery voltage.  This can lead to high voltage/overcharging of the batteries. And, even if perfect when new, a little resistance in all those yards of wire and many connections can give lower than actual readings to the alternator.

I like chassis battery lug of the battery isolator or other source directly connected to the chassis battery by large-gauge wires.

Re: 1991 U300-- bought it!

Reply #142
Mine was Oe that way.  I'm happy with the charge rate and voltage.  13.7 ish.
The duvac charges in cycles. Drops to 12.4 , engages until 13.7    . Sorta like the air system.
 I also have a 100 amp delco running the house side.  The boost combines them of course as does the OE charge controller.

Re: 1991 U300-- bought it!

Reply #143
The powerline alternator was a knock off of a Leece Neville. It was a little cheaper. Foretravel used them for a while. I would have it rebuilt and it is a DUVAC.

Re: 1991 U300-- bought it!

Reply #144
Hehr Powerline is out of Ft Worth, TX.  You can check with them for dealers they trust to rebuild their alternators.

There is one in Pearland where I had one rebuilt a couple of years ago: Alternators and Starters Pearland Alternator Co., Inc. Alternator, alternator...

But, please completely troubleshoot your charging system before doing anything.  A bad battery isolator and bad alternator can have very similar symptoms.

Re: 1991 U300-- bought it!

Reply #145
It is a little bit slow for me to work on the coach since it is in storage now. But I am still working on it.

Follow your guys suggestion and @stump guidance, I did some clean up on the all battery terminals.
Alternator Positive/Negative, Isolator all three posts. Starter solenoid, basically everywhere the battery cable is connected, I used metal wire brush to clean the rust and dirty away. Use some circuit board cleaner to remove grease, then put it back.

After all the cleaning, the voltage is still low on the front voltmeter.  So most likely the alternator is not functioning well.

I called the Hehr powerline manufacture, they said they can certainly rebuild this model 25-15. But it is at least $500. They can sell me a new one Model No. 25-26 for $900, plus tax and shipping, total about $1000. That is a lot of money.

Called the company recommended by @wolfe10 , they said they are able to rebuilt it, but I am not very sure since this one is so old.

One of the HEHR powerline technician told me a trick to test if the alternator is good and just the regulator is bad.
There is a small hole between the two small post. Using a paper clip in stick into the hole and connect with the sense wire, this way, the voltage regulator will be by passed. If the voltage increase with engine RPM increase, then the alternator is good, regulator is bad.

I haven't tried yet. but thought this is good to share to you guys.

When I clean up the connections, I measured the voltage on my battery isolator, I noticed that the three post of the isolator will always hot regardless of the engine running or not. When engine is off, All three post on the isolator show the same voltage. I don't think that is correct based on my understanding on how it works. I think when engine is off, the post connect to the alternator shouldn't have any voltage.

Do I have a bad battery isolator too?


Re: 1991 U300-- bought it!

Reply #146
When I clean up the connections, I measured the voltage on my battery isolator, I noticed that the three post of the isolator will always hot regardless of the engine running or not. When engine is off, All three post on the isolator show the same voltage. I don't think that is correct based on my understanding on how it works. I think when engine is off, the post connect to the alternator shouldn't have any voltage.

Do I have a bad battery isolator too?
Six years ago, not long after we purchased our coach, I encountered this exact same situation with our OEM diode isolator.

I posed the same question to the Forum, and we ended up having a lively discussion about this subject.  See link below:

Bad Isolator?

Note:  The thread linked above does not include my final decision concerning the health of my OEM isolator.  In Reply #22, Peter Fleming (a very sharp Forum member) suggested several tests that required DC current measurement.  I purchased the meter he recommended, and performed the tests.  I came to the conclusion that my OEM isolator was working fine.  I ended up leaving it in place, and it performed exactly as designed for the next 4 years.  Then, two years ago, I removed the (still functioning) OEM isolator during a complete rebuild/upgrade of my isolator panel.

But that's another story:

'93 U280 Isolator Panel Upgrade

Re: 1991 U300-- bought it!

Reply #147
Just  found this topic. Really enjoying it. I have to admire and respect the work your putting into your coach. I have no suggestions from what I've read except that when cleaning the electrical connections, I would be sure to use die electric grease to help prevent future corrosion. Keep the posts coming.

Larry

Re: 1991 U300-- bought it!

Reply #148

When I clean up the connections, I measured the voltage on my battery isolator, I noticed that the three post of the isolator will always hot regardless of the engine running or not. When engine is off, All three post on the isolator show the same voltage. I don't think that is correct based on my understanding on how it works. I think when engine is off, the post connect to the alternator shouldn't have any voltage.

Do I have a bad battery isolator too?


The output terminal on an alternator is always connected to the battery.  Unlike a generator that always has some residual magnetism and because of its design can boot strap that magnetism into full output, an alternator always requires an external source of voltage to start.

Re: 1991 U300-- bought it!

Reply #149
1.  The output terminal on an alternator is always connected to the battery.

2.  ...an alternator always requires an external source of voltage to start.
1.  In the case of the charging system being discussed here (dual batteries, diode isolator + duvac alternator) the output terminal is not connected to the battery.  It is connected to the center post on the diode isolator.

2.  This is correct.  Since, in this case, the output terminal is not connected to the battery, the alternator must receive the voltage by some other means.  Hence the requirement for a voltage SENSE wire which is connected (directly or indirectly) to the start battery positive terminal.

Re: 1991 U300-- bought it!

Reply #150
How's it going, LJ?

Re: 1991 U300-- bought it!

Reply #151

2.  This is correct.  Since, in this case, the output terminal is not connected to the battery, the alternator must receive the voltage by some other means.  Hence the requirement for a voltage SENSE wire which is connected (directly or indirectly) to the start battery positive terminal.

No IGN terminal?

Either way, I guess the gold standard test for the solid state isolator's condition is to lift the wire from the center terminal and measure the voltage present with a finger on the probe to dissipate any stray voltage.

Two lifetimes ago I walked into an auto parts store and asked for a pair of brushes for a Leece Neville.  No questions just some thumbing through a catalog until the question was returned "What kind of a car is a Leece Neville?"

Re: 1991 U300-- bought it!

Reply #152
Some DUVAC style alternators are "self exciting" and do not require a "hot with ignition" wire.  The model 25-15 being discussed above falls into that group.

Other models DO require a external excitation wire and they will have a IGN terminal.

The many variations in alternator wiring setups can cause much confusion.  HAS caused much confusion for our Forum members!

Important to read and understand the wiring instructions/requirements for any replacement alternator...preferably before purchase.

They are NOT "one size fits all".

Re: 1991 U300-- bought it!

Reply #153
Some DUVAC style alternators are "self exciting" and do not require a "hot with ignition" wire.  The model 25-15 being discussed above falls into that group.

Other models DO require a external excitation wire and they will have a IGN terminal.

The many variations in alternator wiring setups can cause much confusion.  HAS caused much confusion for our Forum members!

Important to read and understand the wiring instructions/requirements for any replacement alternator...preferably before purchase.

They are NOT "one size fits all".
Thank you Chuck.  I've enjoyed the discussion, and I think you've left a good trail of bread crumbs* for not only LJ but others.

Me?  I've a Snapper lawnmower clutch to adjust.  Part of the good deed I chose to do for my neighbor in honor of my late sister.

In for a penny, in for a pound.

*GM in their infinite frugality chose to wire the "gen" light to start the alternator, leading to the case where if the bulb burns out the alternator won't start.  The very definition of single point of failure design.

Re: 1991 U300-- bought it!

Reply #154
Just  found this topic. Really enjoying it. I have to admire and respect the work your putting into your coach. I have no suggestions from what I've read except that when cleaning the electrical connections, I would be sure to use die electric grease to help prevent future corrosion. Keep the posts coming.

Larry
I am humbled by the kindnesses here in the forum. I can get this far only because the member here.

The knowledge buried in this forum and the members of the forum is unbelievable. 

What I did so far is nothing compare to what others did to their bus. I still can't wrap my head around how @stump can fix the whole bulkhead by himself. That is serious DIY skill.

Re: 1991 U300-- bought it!

Reply #155
Many alt are exited by a diode and single bulb. Not just GM.  Most cars in the 60s. 

Re: 1991 U300-- bought it!

Reply #156

Alternator changed.

It has been a while since I report back. I am still working on the coach.

As you remember, I was trying to solve the problem of low voltage on the front voltage meter. After few tries, it is clear that the alternator is broken. So I took it out.

@stump mentioned how useful an impact wrench is. So I bought one of the Milwaukee medium torque impact wrench. 600 ft/lb of nut busting torque is enough to handle most scenarios. The big brother has over 1400 ft/lb of torque, but it is too expensive and too big and heavy. I don't think I will ever need that much torque.

With the help of the little impact wrench, taking the alternator out is piece of cake.

After alternator is out, I called to many shops to get a quota to rebuilt. The one @wolfe10 recommended is in Pearland. It is about a hour away from my house. I called them, they are super nice and seems very knowledgeable about power line alternator. They charge minimum $390 to rebuilt the alternator. I mentioned few people on the forum rebuilt their power line alternator for under $300. The owner said that is few years ago. Everything is more expensive now.

I went to another alternator shop that is about 30 minutes away from my house. They are pretty reputable too on alternator rebuild. They bench tested the alternator to confirm that the alternator is broken. The bearing is also need to be replaced. But it seems like they don't want to rebuild the alternator, so they start recommending new units. a KEI heavy duty alternator for $670. A Delco Romey 28SI alternator for $380.

Wait a minutes, If it cost at least $400 to rebuild the alternator, why not buy a new one? If buy a new one, why buy from a local retailer. There are definitely better place to buy online.

So I took my alternator home and start searching options for new alternator or if I can rebuild by myself.

The manufacture of powerline alternator is now HD Power Solutions. They are still in Fort-worth area. I called them few times. They are super nice people. Very helpful. But they said to rebuild the alternator by them, it will be at least $500. They can sell me a newer updated model 25-16 HD alternator for a discounted price of $900 plus tax. That is beyond my budget for a alternator. True it is nice for the alternator to last another 30 years. But I seriously doubt if I am still going to drive the same coach after 30 years. So it is not an economic way for me to invest another $1000 for a 30 years service life.

Their tech support guy is very friendly and helpful. The guy I talked to seems to know everything out of his mind. He has been there for over 25 years. I think he might be the one who build this particular alternator :)) . So he knows inside out the alternator. He even give me his cell phone number so that I can call him any time I want. Absolutely best tech support. With his help, I quickly determined the alternator is broken and it could be as simple as broken brush or a broken rectifier. With it out of the engine bay, I took the voltage regulator off to check the brush. It is pretty obvious that one of the brush has broken metal ribbon. See the picture. So the first step is to find a replacement brush. They seems still have parts available for this model.  Bearing $45 each needs two of them. Brush $15. I might take time to gradually rebuild the alternator by myself later.

So rebuilding alternator might now be an option for the near future. Buying a new one seems to be the better option. My requirement is clear a 200AMP alternator with J-180 mount. Oh boy, there are so many options for the alternator. Price range from $100 all to way to $1200. From 100 AMP to 500 Amp. It is confusing.

Since the alternator shop mentioned Delco Remy 28SI as a replacement, I start looking for this particular model. It seems like this model is very popular for 18 wheeler truck. Nothing too fancy, just a reliable alternator. But finding a geniune Delco Remy online seems to be challenging. There are so many website offering that model, and the price varies greatly.  I think those major auto parts store should have decent price. Autozone, AdvanceAutoParts, Oreilly and NAPA. After looking around on these store website, one particular model on AdvanceAutoParts stands out, it is carquest hd alternator 28SI. Judging form the model no, it is very likely a re-branded Delco Remy 28SI. And most importantly there is a 25% coupon for fathers day. So I places order on Advanced auto parts. It come out at $250 shipped to home. Not bad for a 200AMP alternator from a trusted store. I know I can return to AAP local shop if there is anything wrong.

While waiting for the parts to arrive, I needs to take the pulley out from the old alternator. Again the guy from manufacturer over the phone helped me hand by hand to get the pulley out of the old alternator. Great Tech support. He is surprised that I have an impact wrench. That little boy make things so much easier. As @stump said, it will totally worth the cost if you use it just once. I totally agree with that. With the pulley out, I took the body apart, as you can see from the picture, there are a lot of rust and greasy inside the body. Not sure if it is rebuild-able by DIY.

After few days, the alternator arrived. To my surprise, it is not a Delco Remy 28SI. Instead it is manufactured by WAI.  It seems like WAI is a big auto parts group, they might did the manufacture for or even own the brand of Delco Remy. So it is not a DR 28SI, but it is from the same manufacturer. It should have same quality.

Installed pulley follows Delco Remy 28SI manual. Then installed on the engine. The original cable is too short. I have to cut the zip tie to loose the case to reach the terminal. It pretty tight for the positive and sense wire. I have to pull the wire really hard to get enough to reach to the post. Hope this will not cause any issue in the long run.

Since the tachometer is not reporting accurately. I bought a cheap laser tachometer.. Put tiny reflective tape on the wheel that drives the alternator so that I can use the device to measure the RPM.

After everything is put back, I am super nervous to start the engine. I am afraid I might break something else. But I am glad to see that everything seems to work just fine. The voltage meter show 14V reading now. The tachometer shows 1173 RPM at idle. The Tachometer on the dashboard shows about 860RPM. I think the alternator drive wheel is different from the engine RPM. But both are pretty close. The tachometer might be working fine.

I know it is too long of a post just to change an alternator. Somebody might be able to change it within few minutes. But for people like me who are not very familiar with heavy duty truck, it took some time to get over the initial fear.

Thanks for your reading. Hope it can be helpful to somebody else.
Now I can proudly remove 1 items from my 933 to-do list 8) .









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Re: 1991 U300-- bought it!

Reply #157
The tachometer pulley is smaller than the crank pulley is why rpm reads different. Put the tape on the crank pulley if you want to compare the dash to what the digital reads.

Re: 1991 U300-- bought it!

Reply #158
The tachometer pulley is smaller than the crank pulley is why rpm reads different. Put the tape on the crank pulley if you want to compare the dash to what the digital reads.
Where is the crank pulley?

Edit: fix typo crack => crank