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foxacoon
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Joined: February 11, 2023
Posts: 22
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 Posted: Mon Apr 03, 2023 9:01 pm Post subject: Alt Light Flicker at Idle - Goes out when RPMs go above idle |
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Asking the experts out there…
I Just had a new 1600cc DP motor installed in my 1975 Bus. I’m very happy with it.
1. I’ve put about 400 miles on the new motor. No major issues and break-in is going well.. until… I heard a flapping noise in the engine compartment.
2. Opened the hatch and noticed the belt was super loose.
3. As I was adjusting the belt, I found that it was using 5 shims . I took 3 out and left 2 and that seemed to be the right tension (not positive b/c this is my first time gauging tension on the belt)
4. Started my bus and drove it around and noticed the alternator idiot light started to come on at idle (flickering), but disappears when I start to accelerate.
Any ideas? Could have I tightened the belt too tight? Should I add a shim? Is this a serious issue?
Thanks!
Fox  |
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henk
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Joined: June 28, 2006
Posts: 158
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| Posted: Mon Apr 03, 2023 11:56 pm Post subject: Re: Alt Light Flicker at Idle - Goes out when RPMs go above idle |
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Search here on the forum and yoy will see this happens.
And are you sure it is the alternator light and not the oil pressure light?
How much is your RPM when you idle,might be a bit low?
Henk!!! |
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Cusser
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Joined: October 02, 2006
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Location: Hot Arizona
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busdaddy
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Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Tue Apr 04, 2023 8:09 am Post subject: Re: Alt Light Flicker at Idle - Goes out when RPMs go above idle |
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| henk wrote: |
.............And are you sure it is the alternator light and not the oil pressure light?
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That's what I'd look at first, when you disconnect the oil pressure sensor's wire (key on, engine stopped) does the light you think is oil go out?
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foxacoon
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Joined: February 11, 2023
Posts: 22
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| Posted: Tue Apr 04, 2023 8:27 am Post subject: Re: Alt Light Flicker at Idle - Goes out when RPMs go above idle |
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| busdaddy wrote: |
| henk wrote: |
.............And are you sure it is the alternator light and not the oil pressure light?
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That's what I'd look at first, when you disconnect the oil pressure sensor's wire (key on, engine stopped) does the light you think is oil go out? |
There are two lights on my instrument panel (spedometer). A red light to the left of the turn signal indicator and a green light to the right of the turn signal indicator.
The one that's flickering at idle is the Red Light to the Left of the Turn Signal.
I've tried searching on the forums here, but I might be missing the correct search terms to help me find a related topic and solution.
Any thoughts? |
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mukluk
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Joined: October 18, 2012
Posts: 7452
Location: Clyde, TX
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| Posted: Tue Apr 04, 2023 8:41 am Post subject: Re: Alt Light Flicker at Idle - Goes out when RPMs go above idle |
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| foxacoon wrote: |
| 3. As I was adjusting the belt, I found that it was using 5 shims . I took 3 out and left 2 and that seemed to be the right tension (not positive b/c this is my first time gauging tension on the belt) |
Hopefully you're just talking about the number of shims between the pulley halves and not the total number of shims installed, including those between the spacer and rear pulley half. You need to have eight to ten shims in total, otherwise the two pulley halves won't be properly clamped in place which can lead to belt slippage and damage/destruction of the pulley.
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There are two lights on my instrument panel (spedometer). A red light to the left of the turn signal indicator and a green light to the right of the turn signal indicator.
The one that's flickering at idle is the Red Light to the Left of the Turn Signal. |
It's very easy to accidentally swap the two warning lamps or their wires. To verify the lamps are properly located in the speedometer, disconnect the wire at the oil pressure switch and switch on the ignition -- if the lamps are correct, only the red one will light up.
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kreemoweet
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Joined: March 13, 2008
Posts: 4091
Location: Seattle, WA
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| Posted: Tue Apr 04, 2023 10:43 am Post subject: Re: Alt Light Flicker at Idle - Goes out when RPMs go above idle |
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A flickering alt light, and one that doesn't turn off until throttle is blipped, is very common with the Bosch AL82 alternators, and its imitations. The warning light is a tiny 1.2 Watt thing, and some sources suggest the AL82 was designed for use with a 2 watt bulb (which would pass a little more current). That's what the AL82 I had in my bus did, and I fixed it my wiring a resistor (200 ohms as I recall) in parallel with the warning light.
I've also heard there may be higher-wattage bulbs of the same sort used in the bus dash, I suppose using one of those might also work.
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foxacoon
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Joined: February 11, 2023
Posts: 22
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| Posted: Tue Apr 04, 2023 12:11 pm Post subject: Re: Alt Light Flicker at Idle - Goes out when RPMs go above idle |
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| mukluk wrote: |
| Hopefully you're just talking about the number of shims between the pulley halves and not the total number of shims installed, including those between the spacer and rear pulley half. You need to have eight to ten shims in total, otherwise the two pulley halves won't be properly clamped in place which can lead to belt slippage and damage/destruction of the pulley. |
There were 5 or 6 shims between the top two pulley halves (the ones that create tension on the belt) on the front of the alternator.
After putting about 500 miles on the new motor, the belt lost its tension. So I removed a few shims (stored them behind the nut that keeps the pulley together) and kept about 3 shims between the two halves on the front of the alternator.
Is this what you're asking? |
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mikedjames
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Joined: July 02, 2012
Posts: 3310
Location: Hamble, Hampshire, UK
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| Posted: Thu Apr 06, 2023 1:42 pm Post subject: Re: Alt Light Flicker at Idle - Goes out when RPMs go above idle |
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The flickering Bosch alternator light and needing more RPM can be a sign of worn alternator brushes. Or a loose wire from the alternator B+ to the starter motor. I have had both issues over the years.
Recently I upgraded to a modern aftermarket 75A alternator.. on that the warning light wire is used in different ways talking to a silicon chip.
The alternator goes into a timed soft start when the engine is spinning and power appears on D+ through the warning lamp. If the wire through the warning lamp is loose then the alternator stays in start mode forever.
The lamp then comes on solid during startup and then stays solid on until the RPM increases past a threshold. It comes on solid again if there is a problem..
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