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08-10-2018, 06:11 AM
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#1
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4 Rivet Member
1984 27' Airstream 270
West Chester
, Ohio
Join Date: Jun 2018
Posts: 498
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Alternator belt
Ok...1984 270 with a now new alternator, new pulley 2.5in, new belt, and cleaned drive pulleys. The belt has broken 2x after non-stop squeaking and significant heat. Silent belt when alternator harness is unplugged (no load). Checked pulley alignment and looks perfect. Regularly checking belt tension and is tight but not too tight...I am using NAPA belts. What am I missing here?
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08-10-2018, 07:51 AM
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#2
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Half a Rivet Short
2017 30' Classic
2022 Interstate 24X
Carlisle
, Pennsylvania
Join Date: May 2017
Posts: 15,684
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Hi
Do you have an electrical short on the output of the alternator? One way that could happen is you have one or more dead batteries .....
Bob
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08-10-2018, 08:49 AM
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#3
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Rivet Master
1972 31' Sovereign
1975 31' Excella 500
Currently Looking...
Benton
, Arkansas
Join Date: Mar 2013
Posts: 5,868
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Does the belt you’re using fit the drive pulley? If the belt is too narrow it will drop onto the bottom of the pulley instead of riding on the shoulders of the “V”. This will cause slippage = heat = damage = breakage.
Just throwing that out there.
__________________
The fact that I am opinionated does not presuppose that I am wrong......
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08-10-2018, 09:32 AM
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#4
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4 Rivet Member
1984 27' Airstream 270
West Chester
, Ohio
Join Date: Jun 2018
Posts: 498
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Using Napa part xl 7465. Top of belt is flush with edge of all pulleys. Part look up says this is right part number...
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08-10-2018, 09:44 AM
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#5
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3 Rivet Member
2016 28' International
2015 28' International
2013 28' International
Las Vegas
, Nevada
Join Date: Nov 2016
Posts: 234
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Recheck your electrical connections, disconnect and then see if Alt spins smoothly, sounds like the Alt is "locked" when energized.
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08-10-2018, 12:17 PM
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#6
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4 Rivet Member
1984 27' Airstream 270
West Chester
, Ohio
Join Date: Jun 2018
Posts: 498
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When disconnected, it does spin smoothly with no belt squeak. It’s only squeaking when it’s under a load trying to charge
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08-10-2018, 12:36 PM
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#7
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4 Rivet Member
1984 27' Airstream 270
West Chester
, Ohio
Join Date: Jun 2018
Posts: 498
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What mechanism regulates the Amps that the alternator produces? Maybe I should check that for proper function? I have a newish red top battery for chassis and checked out good
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08-10-2018, 01:42 PM
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#8
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Half a Rivet Short
2017 30' Classic
2022 Interstate 24X
Carlisle
, Pennsylvania
Join Date: May 2017
Posts: 15,684
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Quote:
Originally Posted by Kvsterling
What mechanism regulates the Amps that the alternator produces? Maybe I should check that for proper function? I have a newish red top battery for chassis and checked out good
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Hi
An alternator has a voltage regulator on it that limits the voltage it puts out. The current is limited by the resistance of the windings. If you try to run one into a short ... it'll put out a lot of current .. A multimeter will tell you if the alternator is putting out the right voltage. It also will tell you if your batteries are at some crazy low voltage.
Bob
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08-10-2018, 02:31 PM
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#9
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Rivet Master
1972 31' Sovereign
1975 31' Excella 500
Currently Looking...
Benton
, Arkansas
Join Date: Mar 2013
Posts: 5,868
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Quote:
Originally Posted by J. Morgan
Does the belt you’re using fit the drive pulley? If the belt is too narrow it will drop onto the bottom of the pulley instead of riding on the shoulders of the “V”. This will cause slippage = heat = damage = breakage.
Just throwing that out there.
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V belt pulleys CAN wear out, but it takes a LOT of use to do that, usually hundreds of thousands of miles.
You might try one size wider belt just for kicks. I have done that with worn pulleys with great success.
I just don’t believe that a typical alternator can be loaded up enough to snap belts.... something else is up in my opinion..... maybe your Napa got hold of a bad batch?
__________________
The fact that I am opinionated does not presuppose that I am wrong......
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08-10-2018, 02:32 PM
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#10
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3 Rivet Member
2016 28' International
2015 28' International
2013 28' International
Las Vegas
, Nevada
Join Date: Nov 2016
Posts: 234
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Quote:
Originally Posted by uncle_bob
Hi
An alternator has a voltage regulator on it that limits the voltage it puts out. The current is limited by the resistance of the windings. If you try to run one into a short ... it'll put out a lot of current .. A multimeter will tell you if the alternator is putting out the right voltage. It also will tell you if your batteries are at some crazy low voltage.
Bob
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and when the alternator dies, it usually takes the VR with it. Listen to Bob!
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08-10-2018, 02:41 PM
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#11
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4 Rivet Member
1984 27' Airstream 270
West Chester
, Ohio
Join Date: Jun 2018
Posts: 498
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Thanks bob, the alternator that was replaced tested putting out almost 15v. I have not checked the new one but maybe there is some electrical gremlins outside of my alternator hardware and there is nothing wrong with the belt...
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08-10-2018, 04:08 PM
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#12
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4 Rivet Member
1984 27' Airstream 270
West Chester
, Ohio
Join Date: Jun 2018
Posts: 498
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I’m going to try a larger belt and battery check. This week the belt broke with a new Napa belt on a new pulley mounted to a new alternator. It squeaked non stop for about 20 miles then failed with the heat build up. The rubber on sides of the belt was slick and partially melted
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08-10-2018, 04:10 PM
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#13
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Rivet Master
2005 34' Classic S/O
2006 39' Land Yacht 396 XL
north blenheim
, New York
Join Date: Sep 2012
Posts: 2,847
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Did you ever think that it maybe the water pump ???
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08-11-2018, 09:11 AM
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#14
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Half a Rivet Short
2017 30' Classic
2022 Interstate 24X
Carlisle
, Pennsylvania
Join Date: May 2017
Posts: 15,684
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Quote:
Originally Posted by Kvsterling
I’m going to try a larger belt and battery check. This week the belt broke with a new Napa belt on a new pulley mounted to a new alternator. It squeaked non stop for about 20 miles then failed with the heat build up. The rubber on sides of the belt was slick and partially melted
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Hi
Continuing to run into what likely is a fault in the electrical system is a very good way to do a *lot* of damage to the electrical system. The cheapest part of it would be burning out the new alternator. Frying this and that downstream in the system simply adds to the bill. Worst case is probably a fire. Having a fire in an RV is no fun at all. Having that when moving 60+ mph down the road .... yikes !!!
Bob
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08-12-2018, 07:30 AM
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#15
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4 Rivet Member
1984 27' Airstream 270
West Chester
, Ohio
Join Date: Jun 2018
Posts: 498
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So the voltage regulator was bad on the 2-week old alternator! Replaced it under warranty and upgraded to 94A alternator. So far the belt squeak is gone and voltage gauge reads normal. We had a full system check (coach) by RV shop and everything checked out. 2 fire extinguishers on board in case
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08-13-2018, 06:02 AM
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#16
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4 Rivet Member
1984 27' Airstream 270
West Chester
, Ohio
Join Date: Jun 2018
Posts: 498
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Regarding the well known 454 alternator belt issues, I was reading the chassis service manual. Found that the alternator is to have a higher belt tension than the ac or PS belts. It is also to be re-tensioned after 30 minutes/15 Miles of driving, 8 hrs/240mi, and re-tightened every 200 hr/6000mi. I confess I did not know this procedure and may have been part of my belt failure experience. I will be checking water pump bearing situation this week
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