'78 bus alternator light flickers

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honeybus
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Location: Aldie VA
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'78 bus alternator light flickers

Post by honeybus » Mon Jan 21, 2019 4:30 pm

I fully charge the battery via battery charger.

I start the bus. I see reading of 13 volts charge. Alternator light @ dash goes from BRIGHT RED to OUT, So far, so good

About 60 - 80 seconds later, the alternator light comes on very DIM. I observed this 60 - 80 second 'waiting period' between startup (alt light OUT) to alt light DIM each time I started the engine.

Foot on gas, and alternator light goes from DIM to BRIGHT RED.

The 13 volts charge at startup drops to battery level (12.0) as alt light goes from OUT to DIM.

Volt regulator checked out OK (resistance checked) before the above test (don't know what resistance is when alternator light goes dim)

Ideas? What's happening? I just received a rebuilt alt last week, and intend to install it if current alt is tested and shown to be not good.

Barry sends
Thank you for all the fish . . .

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Amskeptic
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Re: '78 bus alternator light flickers

Post by Amskeptic » Mon Jan 21, 2019 9:27 pm

honeybus wrote:
Mon Jan 21, 2019 4:30 pm
I fully charge the battery via battery charger.

I start the bus. I see reading of 13 volts charge. Alternator light @ dash goes from BRIGHT RED to OUT, So far, so good

About 60 - 80 seconds later, the alternator light comes on very DIM. I observed this 60 - 80 second 'waiting period' between startup (alt light OUT) to alt light DIM each time I started the engine.

Foot on gas, and alternator light goes from DIM to BRIGHT RED.

The 13 volts charge at startup drops to battery level (12.0) as alt light goes from OUT to DIM.

Volt regulator checked out OK (resistance checked) before the above test (don't know what resistance is when alternator light goes dim)

Ideas? What's happening? I just received a rebuilt alt last week, and intend to install it if current alt is tested and shown to be not good.

Barry sends

Hey Barry,

Please do your due diligence first. Disconnect negative battery cable from battery. Clean all grounds, both ends on the battery ground cable and the transaxle ground strap. Clean all terminals on the battery and the starter solenoid while the negative cable is off the negative battery post. Look for the alternator charge wire (B+) that terminates at the starter solenoid post, and check very carefully for any corrosion between the wire strands and the eyelet terminal. Clean the eyelet shiny clean, and clean all the others too (especially the big red/white wire that goes directly to the fuse box!), then reconnect to solenoid post. Do NOT overtighten the 13mm nut.

Check the wiring harness from the alternator to the starter and the branch to the voltage regulator. The voltage regulator plug must be checked for any evidence of heat or loose connectors in the molex plug. Follow the blue wire off the voltage regulator plug to the single connector. Make sure spade terminals are securely crimped onto the wires. When you plug the voltage regulator plug back in, check that the wires are all fully seated on the regulator blade terminals.

When you are all clean and secure, reattch the positive battery cable first, then the negative. Then check again for the dim red idiot light. If it is still misbehaving,it is likely that you have a blown diode in the excitor circuit of the alternator.
Colin
BobD - 78 Bus . . . 112,660 miles
Chloe - 70 bus . . . 206,845 miles
Naranja - 77 Westy . . . 116,898 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 91 Lexus LS400 . . . 84,465 miles

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honeybus
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Re: '78 bus alternator light flickers

Post by honeybus » Tue Jan 22, 2019 11:24 am

Thanks, Colin.

Sadly, it is getting more difficult to do much with the bus anymore. 'Due diligence' is now only a 'concept'. Basic maintenance is challenging (oil changes; R&R alternator belt; adjust rear brakes or even toot the horn).

I was expecting to prepare the bus for its annual trip to Florida in March - April; spring break, you know - Key West and all. Four weeks ago I had thoughts of pulling the alternator and taking it to a shop for checking (Advance Auto -) Now, I expect to call on a mobile mechanic to come by the NEW house and help me with the alternator. He is an old school VW mechanic in Manassas Virginia. I would take it to a shop in Manassas Virginia (another old school VW air cooled, and his special interest is bay window buses) but the recent storms in Virginia have caused the roads to be salted, and this 'garage queen' aint about to get her belly salted!

I believe my VW adventures are about to come to a close. I still have a bunch of nuts & bolts and niceties that need a new home, but I figure my wife can handle that if I just mark the boxes 'VW'. Probably about fifty boxes, plus various non-VW hand tools.

So, I cannot do your check list because of my physical limitations. Last March 2018 in Key West, I was able to fix my right rear tire (flat) by jacking up the bus, (no jack stands available), remove the tire, remove the embedded dry wall screw from the tire, plug the hole, swap the tire with the spare off the front, lower the bus and drive to a compressed air pump. Then I . . . , re-exchanging the two tires. Today, the hub cap would be challenging.

Again, thank you for your professional comradeship. I was thinking the 60 - -80 second delay (a repeatable event) would give insight. Possibly/probably a diode.

I expect I cannot test the alternator without the pulley (sic), which needs to be moved to the rebuilt alternator, unless I become able to pull the alternator myself (can't have the mobile mechanic come by twice for the same job to satisfy my curiosity! ) . But if I become physically capable to pull the alt, I should be able to install, so then I probably won't need the mobile mechanic at all!

I have seen the videos and discussions about the too-tall B+ post, so I will be careful. (The Bosch rebuild alt B+ post definitely has a lot of extra thread; the other rebuild alt post WASHER is well insulated so that will not interact electrically with the alt backing plate; I anticipate a clean, unbroken, flexible alt cooling boot)

BTW, I looked but I haven't found your 2019 itinerary. What's up?

Homefront news! My Korean wife, Sun, got her Tae Kwon Do Black Belt last Friday at the age of 67. My son Jason married a Russian girl a bit back, My daughter Jenna (West Point grad 2008,still unmarried) promoted to Major in the US Army, in residence at Ft Belvoir hospital to complete her MBA / MHA from Baylor (still unmarried) with a didactic GPA score for 78 course credits of 3.912! (still unmarried, but I guess you knew that by now.)

OK, bye for now.
Thank you for all the fish . . .

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Amskeptic
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Re: '78 bus alternator light flickers

Post by Amskeptic » Tue Jan 22, 2019 11:45 am

honeybus wrote:
Tue Jan 22, 2019 11:24 am
Thanks, Colin.
My Korean wife, Sun, got her Tae Kwon Do Black Belt last Friday at the age of 67.
My son Jason married a Russian girl a bit back,
My daughter Jenna (West Point grad 2008,still unmarried) promoted to Major in the US Army, in residence at Ft Belvoir hospital to complete her MBA / MHA from Baylor (still unmarried) with a didactic GPA score for 78 course credits of 3.912! (still unmarried, but I guess you knew that by now.)

OK, bye for now.
Hello Barry,
I enjoyed my visits with you.

Tell Sun I said "hello" and still panic when stepping into any house with all of the shoes parked at the door.

Tell Jenna she could not do any better than to marry me.
Colin :blackeye:
BobD - 78 Bus . . . 112,660 miles
Chloe - 70 bus . . . 206,845 miles
Naranja - 77 Westy . . . 116,898 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 91 Lexus LS400 . . . 84,465 miles

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