79 CBX battery not charging


79 CBX battery not charging

Postby stevenmelching » Sun Sep 01, 2019 8:56 pm

Hello. 79 CBX newbie here. Have a new battery but not charging. Put voltmeter on battery key turned off shows approx 11.6 volts. Start bike run rpm up to approx 2800 rpm voltage drops to approx 11.2 volts. Check all connectors behind right side cover all looks good. Decide to try a new Ricks voltage regulator and voltage at 2800rpm now showing approx 13.0 volts so thinking that was my problem. Bike runs great for awhile than dies. All lights etc dead. Check main 30a fuse on right side. Tap the fuse and it falls apart? Main fuse ready to die? Put a temp jump wire across fuse ports bike fires right up. Could it be as simple now as a bad fuse ready to die? Now have to wait for fuse to come in. Is there a safe simple way to get a 30 amp fuse locally to put on temporarily?
Thanks
Steve
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Re: 79 CBX battery not charging

Postby daves79x » Mon Sep 02, 2019 7:42 am

Welcome! First, you need to renew your fuse with the correct 30 amp strip fuse. Your local Honda dealer should carry them. Or eliminate the Honda set-up with a modern replacement fuse holder. This is a good lesson for everyone - the stock strip fuses get brittle with age and should be replaced (along with the spare) every few years.

But I doubt this was your problem. Your alternator needs removed and evaluated. First is to check brush wear. These can wear brushes out (the outside one) in less than 10,000 miles. If those are OK, then check the resistance between the rotor's slip rings. It must be 3.8-4.2 OHM. Higher or lower is bad and it needs rewound. That is your likely problem. Also make sure your connector to the wiring harness from the alternator is not melted.

There are volumes written here about diagnosing alternator problems. There is more to check while your alternator is apart. Do a search and see.

Dave
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Re: 79 CBX battery not charging

Postby stevenmelching » Mon Sep 02, 2019 10:19 am

Thank you. Follow up question please. A new Ricks voltage regulator should not be running hot to the touch after engine warm up correct?
Thank you
Steve
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Re: 79 CBX battery not charging

Postby Rick Pope » Mon Sep 02, 2019 9:05 pm

I'm not an electrician, nor even a good mechanic, and I rarely stay at Holiday Inns. But, it would seem to me that part of the regulator's job is to convert the ac current from the alternator to dc, which keeps the battery happy. So, if that's the case, half the current would be given off as heat. Hopefully, an electrical guru will come by soon.........
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Re: 79 CBX battery not charging

Postby daves79x » Tue Sep 03, 2019 8:27 am

They run a lot hotter when in use with a bad rotor. That's why the whole charging system needs evaluated. A bad rotor can and will eventually take out other components.

Dave
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Re: 79 CBX battery not charging

Postby stevenmelching » Tue Sep 03, 2019 1:58 pm

Thanks guys. Replaced the voltage regulator and it fixed the charging issue. Still going to have my friend Jan next weekend at Marrietta go thru the alternator also and check it thoroughly to be safe. Have a brand new stator and brushes ready to go if needed.
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Re: 79 CBX battery not charging

Postby EMS » Wed Sep 04, 2019 8:43 am

I am sure you did this when you replaced the regulator, but the contacts in the red plug need to be checked. Corrosion in there will make for poor contact, increased resistance, increased heat, poor charging and eventually melting of the plug.
Mundane issue, but important. A new regulator will not help this.
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Re: 79 CBX battery not charging

Postby Larry Zimmer » Wed Sep 04, 2019 1:00 pm

Exactly, Mike!! As little as 0.5 ohm through those contacts will loose 2.5 volts with a measly 5 amp charge.
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Re: 79 CBX battery not charging

Postby NobleHops » Tue Oct 01, 2019 10:24 am

EMS wrote:I am sure you did this when you replaced the regulator, but the contacts in the red plug need to be checked. Corrosion in there will make for poor contact, increased resistance, increased heat, poor charging and eventually melting of the plug.
Mundane issue, but important. A new regulator will not help this.


This, 100%, but also the smaller red connector under the right-side cover that leads to that fuse holder is also a known trouble spot, frequently melted. We have taken to ultrasonic cleaning all of these connectors at minimum, and we will frequently extract the spades and sockets from them, trim to fresh wire and re-crimp new ends to restore good connectivity. Once these connectors are absolutely clean, take a pea-sized blob of silicone dielectric grease, smush it into the female side of the connector, and remake the connection, and that should keep that spiffy for a good long while.

We are also fond of ditching that entire subharness with the fusible link in favor of a modern 30 amp ATC fuse holder, and of course while doing that we are replacing all of the spades and sockets.

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