72d18, electrical short, battery questions.

[Thenoob]

Soooooo
I hooked up my battery to start it and right away smelled something burning , unhooked the battery and got under the dash and this is what we see.  This connection goes right to the steering wheel.  Any ideas where to start to find out what's causing it? Hard repair?

And I also have some noob rv battery questions.  We all know how to hook up a battery.  But my cables are not identified which is which.  We obviously know the negatives are at the solenoid and the other 2 are both positives, but how do you know your connecting the right negative off the solenoid with the right positive? I am thinking this stupid 50% guess could have done the damage?

Any help would be great!

[PwrWgnWalt]

First - since I cannot tell exactly how your MH is wired, the following is just for your consideration 


On my custom-made battery cables, the positive lines have the red fitting clamps (plastic/nylon), as shown in your photos at the terminal ends where the cable attaches to the solenoid.  On mine, the positive side of the battery powers everything (goes to all the connections).


Since my Dodge MH chassis is a 'negative ground' (other Dodge's are too, in every instance I am aware of), the negative cable on mine goes to the chassis.


A good wiring diagram, like that found on this site in the Member Area and various posts, would help you immensely!  Look up some of Dave's posts on wiring, they are excellent and show pictures.


It appears you may have been making a full-current (or very high) circuit through the small connector, perhaps as a result of mis-wiring the battery connections.   D:oH!

Once you figure out what cable goes where... MARK THEM!

[Thenoob]

I'll def be upgrading my membership next week, appreciate the detailed response.

Trying to figure out if there's a way to safely test which terminals
Are for the engine and which ones are for the coach lol

[Thenoob]

Well I think I found it, but need help with identifying where it goes.

So, where the negative cable
Goes from the solenoid, there's a wingnut holding down three cables.
1 goes to the starter
1 goes to the solenoid where the batteries are stored
The other, well she's fried.  Split
In half fried.

If you remove the doghouse, closest to
You straight down there is a bank of wires and such right above the engine.  That cable that's destroyed runs into there somewhere, I'm guessing it has to do with starter/ignition??? I've included pics, hook g someone can chime in??  Just so it makes sense , where the fried cable runs to is that bank
Of wires in front of the dist cap, hopefully the pics makes sense.  If anyone can tell me what cable that was that fried... Awesome.

Thanks in advance!!

[Rickf1985]

That is a fusible link, it is designed to do that in case of a short circuit to protect the rest of the wiring. You either have a short in that circuit or if as you keep saying about having the NEGATIVE cable hooked to this then you had the battery cables reversed and you have probably fried several things. The POSITIVE cable goes to the solenoid and the negative cable goes to the body and/or the frame of the vehicle. I don't care what color the wires are, that is how they have to go. You can buy those fusible links at any automotive store, the size might be marked on the tag or a lot of times you can go by the color. Take that one to the store with you. Get the cables lined up right and hook up the positive cable to the battery and to the solenoid, or where ever the POSITIVE cable from the battery is supposed to go. Usually the solenoid. Then just tap the other cable to the negative battery post and see if you get sparks. If you get a lot of sparks then you are going to have to find all of the burnt wiring before doing anything else. I suggest you try this before hooking up the new fusible link. If you get no sparks then leave the cable off of the battery and hook up the fusible link and then tap the cable to the battery again. If no sparks then the shorts are not present at that time. I would still leave the negative cable off until you go over all of the wiring to be sure it is all good. If you did in fact hook up the battery backwards as it seems you did then be prepared to have to replace the alternator, regulator and ignition module. Not saying they will definitely be bad but there is a good chance so if it does not start or does not charge you will know why. That bank of wires by the distributor cap is going to the ignition module.

[Thenoob]

Thank you for the detailed write up and everything makes sense.


The good news is there are no other fried wires from what I can see on top and umodern earth the coach, everything else looks fine from the starter to the module.

[Thenoob]

The good news is there are no other fried wires from what I can see on top and umodern earth the coach, everything else looks fine from the starter to the module.

[DaveVA78Chieftain]

The fusible link is 14 gauge
One end connects to the B+ terminal on the starter solenoid
Other end connects to the 10 gauge red wire that goes to the Ammeter in the dash.

[Thenoob]

And from there inside the cab to this black wire in this cluster that runs into the steering wheel.  Only wire that got messed up.  Now to look over the factory electrical and figure this out

[Froggy1936]

If all the other connections are ok The easiest way is to just add a jumper over the connector. Cut the original wire off beyond the damaged area and solder in a jumper of the same size wire The problem came from high amperage thru a lousy  connection Not any malfunction. It was a engineering failure ! Frank

[DaveVA78Chieftain]

That is the main battery wire A20B(12BK) from the Ammeter that feeds the ignition switch.

[Thenoob]

Ahhhhhhhh it all makes sense now. 
Before it melted I'd have to give a little wiggle sometimes to that connector for the motor to start.

I understand now, thanks yall.  Now to fix, man I hate electrical

[Rickf1985]

You might want to look at the red and black wires under that burnt connection in that last picture, it appears that maybe the red wire has melted into the black one a bit. The red wire also looks questionable to the right by the connector.

[Oz]

...  Now to fix, man I hate electrical

I sympathize...

[Thenoob]

Vroooooooom goes the Winnie as the 318 roars to life.
Problem fixed for the most part, lots of learning.

Another question, my fuel hasn't worked since I got it, put the test light on the points and all lights up,  that's when I went what in the world, why isn't there anything on these points??? Am I wrong or is that te obvious reason it isn't working?  Where are the wires that should be crimped and on the points?

Also found this thicker black wire floating around.  Now the white wire it's jumbled with plugs into the "battery/dual/mon/ guage and there is an open point, if anybody knows that this is where that one goes would be awesome, I know im reaching a bit but maybe someone does.

Thanks for all the help!!!!!

[Thenoob]

So what it looks like is I have a missing white wire?  Still getting used to this thing.
Now fix the fuel guage and figure out why my stereo isn't running

[Thenoob]

Looks like I found my white wire but then poof another problem all of a sudden no power.

I have a question. About the ammeter. Are all
Those points power points  acting as power points for different stuff? I think the small one that's clipped on there looks like it's running to a cd deck that doesn't work... Weird thing is my buddy pulled it out and put it back and all
Of a sudden there is no
Power to anything.... I'm hoping it was because the battery needs to be charged up because I only ran the rig for 5-10 mins after sitting for a year....


I know the big black
One is supposed to be connected I'm referring to the blue one.  But
Man it was nice when she was running, purring, but
I need to figure out these issues!!!

[Thenoob]

[Thenoob]

Got it going again after a full battery charge
But what's happening is looking like a bad ignition switch???

Turn turn turn, nothing no
Power then all of a sudden vroooooom.

[DaveVA78Chieftain]

Work one problem at a time.  Jumping back and forth between fuel circuit and starter circuit will only confuse everyone.
Starter circuit - Could be:
Bad wiring connection
Bad ground connection
Ignition switch
Starter Solenoid
Starter

You have to work from point to point through the wiring diagram with a multimeter from say the burnt connector that feeds the ignition switch.
Is there voltage at each point when you place the key to start?
Is there excessive voltage drop when you place the key to start?

[Thenoob]

I figured it Out  It's that 7 pin connector that got fried , a little Wiggle and she goes, switched out Tomorrow.  Fuel guage is next.

[DaveVA78Chieftain]

Fuel and temp gauges are electro-thermal devices that require a constant voltage source.  For that year model, that 5VDC constant voltage source is built into Fuel gauge.
On fuel gauge:
Pin "I": 12VDC input (copper bus bar from ammeter)
Pin "A" [F12(18DB)]: Constant voltage output to temp gauge (18 gauge dark blue wire)
Pin "S" [F13(18LB)]: Fuel level sender input (18 gauge light blue wire)

Fuel Sender
10 to 73 ohms

Tank empty: 73 ohms (max resistance like an open circuit)
Tank full: 10 ohms (least resistance like a short to ground)

Do you have dual tanks which require a tank select switch?

[Thenoob]

Negative single tank sir.
It's t'd underneath running to the gen shack

[Oz]

Are you now troubleshooting gauges? 

There's a tech article on 1973 fuel gauge problem in the Member Area - Mechanics 101

It goes through the process in detail with pictures.