Elec Question -Bus Frame DC Neg/Ground

[Seangie]

My wife & I got a babysitter and got to take the bus out for a night on the town. (Walmart parking lot   ). It was exciting and fun and a great learning experience.  One of the issues that we had was that one of the headlights went out,  I went out to see if it was a bad lamp and in the process of removing the cover the headlight came back on.  I also noticed bleedover on the high beams (they were off but very dimly lit) and the PO said he had the same problem and attributed it to a grounding issue.

After taking a look through the bus I noticed that a lot of the DC neg wires were just tappped into the bus frame and not run back to a block.  In theory this works as the bus's negative post is hooked directly to the frame.  My question is...should all the DC neg leads be hooked to the bus frame?  Is this common?  Wouldn't it be better to run all the negs back to a block and ground the block? 

Curious to see how others are wiring out there in bus land (and excitedly waiting for Sean to post!!) 

Thanks to all.  Hope you had a wonderful weekend.

-Sean 

[travelingfools]

In my 87 MC9, I had multiple problems. I finally rewired them powering them directly from the start  battery (12 volt). The old system was a nightmare. Best thing I ever did.

[eagle19952]

chk/replace dimmer switch.

[chev49]

Yesterday I removed 4 ground wires bolted to the light housing... Grounds should at least be run to a terminal block with heavier wire back to batteries. Last week I ran new welding cable front to back, both positive and negative so i can properly hook ground, generator etc up.  I hate grounding problems.

And from the bus fire post, I'm gonna go back and add another wire loom on top of the one i have.. will be overkill but 2 layers of that over the wire should be safe.

[buswarrior]

I expect you will find the ground wires a mess on each headlight, and the dimmer switch will be a corroded mess.

Dimmer switch is inexpensive at the local truck parts place.

Yes, most of it grounds locally to the body, same as much of our personal autos.

Headlight wiring is a common replacement job for a busnut. Once done, trouble is gone.

happy coaching!
buswarrior

[rv_safetyman]

Sean, from the Eagles International site, I see that you have an '84 Eagle 10s (would suggest you update your signature here so that folks can focus their comments based on your bus).

Each of the headlight circuits goes through a breaker on the electrical panel under the driver's window.  After a lot of years of service, their ability to make contact and transmit a fair amount of current is compromised.  I set up a relay system down behind the front bumper.  I use the wiring that went to the headlights only as a signal to the relays.  That way, the headlight switch, dimmer switch, breakers and wire only have to transmit a very low current (less than 2 amps).  

I ran a heavy supply wire (protected by a 30 amp breaker) down to the relays and that feeds the headlights via the relays.  I also ran a heavy ground wire to a stud type terminal strip and then hooked the headlight grounds to the ground stud.

I detail all of this (with photos and wiring diagrams) in the Nov. 2011 issue of BCM magazine.  In that article, I detail the relays I used and give you sources.

One last comment.  It is good that you a new HD supply line and ground to the front of the bus.  I would suggest that you put a good fuse on that positive supply cable to protect you in the event that your cable would short out.  Sounds like you have it well protected, but I still believe in Murphy.

Jim

[luvrbus]

Do as Jim suggests also start at the back at ground terminal where the ground for the starter is mounted on the frame and work forward, your bus shows ground buse bars in the rear panel and front panel with the head lights connected to the ground buse bar and by the way of a ground strap also from the frame to the head light buckets on each side

good luck

[Sean]

Sean, you've gotten lots of good guidance in this thread, and I don't have much to add about the headlights specifically.  Other Eagle owners are a better resource than me in this regard, and especially my good friend Jim Shepherd (rv_safetyman) who has gone to great lengths to document everything.

That said, I do want to respond to this question:

... After taking a look through the bus I noticed that a lot of the DC neg wires were just tappped into the bus frame and not run back to a block.  In theory this works as the bus's negative post is hooked directly to the frame.  My question is...should all the DC neg leads be hooked to the bus frame?  Is this common?  Wouldn't it be better to run all the negs back to a block and ground the block? 

As it turns out, this is something of a religious debate, with fanatical proponents on both sides.

Personally, I don't care for chassis-return wiring, for a bunch of reasons which I have detailed elsewhere on the board.  But I am more of a centrist on this issue; I tend to leave existing, OEM-installed wiring that already uses chassis-return as it is, unless and until any given circuit starts having ground problems.  Then it is a case-by-case judgment call whether to repair a chassis ground or home-run a new ground back to the distribution panel.

When installing new wiring, such as for a house DC system, I prefer to use all home-run direct return, and keep the house current out of the chassis altogether.  The house DC negative does still need to be bonded to the chassis near the negative house battery post, but I like to put a large negative return from the distribution panel on that same post, so no current runs through the chassis.

That said, since your conversion is already complete, I would not be overly concerned about existing chassis-return house loads such as 12v lighting.  The only exception would be anything really high-current, such as an inverter and/or charger, which should have dedicated negative wiring.  You might want to ensure that all motors, such as water pumps, have dedicated negative return wiring as well, just to keep the electrical noise out of the chassis to reduce EMI.

HTH,

-Sean
http://OurOdyssey.BlogSpot.com

[bevans6]

Sean's way is my way too.  I leave (but maintain) any chassis return grounds that I come across, which means virtually all of the bus chassis itself (except for the clearance lights, which I haven't figure out yet - they each have a separate ground wire.  I don't know if that wire goes to a local ground or gets run back to somewhere).  But I do all of the "house" wiring with home-run grounds.  What I do to make that easy is unroll a pair of 50 foot or 100 foot rolls of house wire in two different colours, tie off one end and chuck the other end in my cordless drill.  Pull tight and spin the pair of wires into a very neat and tidy twisted pair...  Easy now to pull through to where you need it.

Brian

[Uglydog56]

Something I learned from a racecar builder from the nitrous cars which are real picky about grounds.  If you are having issues with corrosion in your grounds to frame, pick a few convenient points, weld a stainless steel bolt (I usually use 5/16) to the frame there and connect your grounds to that stud.  Vaseline helps, don't use anti-seize it is electrically insulating.

[Sean]

... weld a stainless steel bolt (I usually use 5/16) to the frame ...

I advise against using stainless for this, especially if it will be for a high-current application such as a main battery or alternator connection, because stainless is a poor conductor and this can lead to ohmic heating.  Since the last time I wrote about this subject (http://www.busconversions.com/bbs/index.php?topic=18140.msg195614#msg195614), I can now say that I am aware of a fire that started at a stainless washer.

Copper, brass, or even carbon steel are all better choices than stainless for this application.

Vaseline helps, ...

While petroleum jelly will work if it is the only thing available, I recommend instead to use dielectric grease, which is silicone-based and is specifically designed to protect electrical connections from corrosion.

FWIW.

-Sean
http://OurOdyssey.BlogSpot.com

[buswarrior]

I like the anti-seize with the copper mixed in the goop for ground connections.

Best not used for the positive side...!!!!

happy coaching!
buswarrior

[Oonrahnjay]

My mama always said "there's nothing as good as a good marriage and nothing as bad as a bad one".  I think the same thing could be said for grounds -- if they're not about perfect, they can be the source for lots of problems!

[belfert]

Why do group 31 batteries always seem to come with stainless washers and nuts if they are so bad?  I believe the marine bus bars I have used are also stainless.

[luvrbus]

Yep group 31 batteries come with S/S studs,nuts and washers sure glad you ask Belfert lol so do a lot of the 8D AGM batteries some also use nickel plated studs

good luck