Turn The Key And Nothing Happens

[3Ms75Argosy]

my heart bleeds for you. Please keep going, Chummy will be better eventually!

Any thought on getting a new isolator and trying that? I find it odd that power gets to it, then seems to stop from there. I can't figure out how disassembling the dash got into this mess, but, it seems from your posts that the isolator is the "router" of power to the fuseblock. I think your MH is too old for some sort of hidden theft immoblizer (activated when the ignition lock was disconnected), right?

I'd also suggest "jumping" the fuseblock - passing the isolator - but I'm not sure if the isolator steps down the current to the fuseblock.

[Chaplain Kent]

Originally Posted by 3Ms75Argosy

I'd also suggest "jumping" the fuseblock - passing the isolator - but I'm not sure if the isolator steps down the current to the fuseblock.

I have thought of this as well. Can anyone else tell me which posts of the isolator are hot? I have only the far left post which is hot. The middle post circles back to a post under my alternator- could this be the source of power for my fuse block? There is no current at this post. It is my understanding that this post would be hot when the engine is running.
Can I by-pass the isolator and just try and see what will happen operating off of the cranking battery?

[guy99]

Man this really sucks, I am really sorry you are going thru this. But, we all know that some day Chummy will run again.

There is no reason that you need to have the isolator in the circuit that connects the chassis battery to the igniton or the fuse block. All the isolator does is to connect the chassis battery and the house batteries WHEN THE ALTERNATOR IS PUTTING OUT CURRENT. You should be able to wire the chassis battery to the alternator, starter and all other circuits powered by the chassis battery without the isolator. If you did, the only functionality you would lose is the ability to charge the house batteries via the alternator.

[garry]

The most logical place to check is the missing positive voltage. However; I am wondering if you have verified the ground (negative) side of the battery is OK by checking with an ohm meter from the negative post to engine ground ?

After reading your post several times the places you have the positive voltage could be from the house battery. A missing negative from the starting battery would give you all the same symptoms you have outlined.

Garry

[GlenCoombe]

There is no reason that you need to have the isolator in the circuit that connects the chassis battery to the igniton or the fuse block. All the isolator does is to connect the chassis battery and the house batteries WHEN THE ALTERNATOR IS PUTTING OUT CURRENT.

Guy, I thought the isolator also joined the batteries for starting purposes? Maybe it's just a delusion.... I'm often out of my mind... kinda like Lev.

Kent, I've been following the thread since last week. Hope you're getting back to normal this week. Sorry for your troubles.

[ralley]

Originally Posted by GlenCoombe

There is no reason that you need to have the isolator in the circuit that connects the chassis battery to the igniton or the fuse block. All the isolator does is to connect the chassis battery and the house batteries WHEN THE ALTERNATOR IS PUTTING OUT CURRENT.

Guy, I thought the isolator also joined the batteries for starting purposes? Maybe it's just a delusion.... I'm often out of my mind... kinda like Lev.

Kent, I've been following the thread since last week. Hope you're getting back to normal this week. Sorry for your troubles.

Ch Kent:

Battery isolators are intended to isolate batteries in different "banks" so current can flow from the charging system (alternator) into each "bank", but not backwards to the alternator or from one "bank"to another. This protects a charged "bank" from discharging into a weak one. They work using diodes, which only allow current to flow one way. There will be a slight voltage drop.

In a previous post, I think you indicated that you had measurable voltage at only one post on the isolator. If so, this is a problem. Both outer posts ought to give you measurable voltage, one from your starting battery and one from the house batteries.

You can, as indicated elsewhere here, join all the wires on the isolator which bypasses it entirely, which might be useful for testing purposes.

[garry]

You say “There is no power to either side of the fuse block. There is no power to the ignition switch. There is no power to the glow plug switch, horn, head lights or anywhere past that fuse block”.
No one that has come to look at this has yet to tell me how power is getting to the fuse block.

IMHO;The power does not come from any “one” wire at the fuse block. Some of the wires are hot with the key “on” others are hot all the time. “These” wires are to connect the positive side of the battery thru fuses and then to the components and back to the negative side of the battery via chassis ground.

Some of the wires are taking the voltage into the cab area and some are taking the voltage out to various components outside the cab area. The fuse block is only a junction area where (most) everything is protected from short circuits.
To make it all work you have to have a path starting from the “negative” battery post to the positive post with whatever components requires the power in between and these components will be protected by a fuse, CB or fuseable link.
Based on your statement of what doesn’t work a major wire from the negative or positive post of the battery just isn’t making a connection (open circuit).

John HD has outlined a good way to start with the basics of troubleshooting an open wire, you can also use an ohm meter.I think you will have to start with just one item (forget the key) pick something that should have power all the time like a headlight or parking light turn the light switch on and go from there. When you find the problem why the lights don’t work everything else will fall into place.

Garry

(had to edit to make it readable)

[azflycaster]

Garry is 100% correct. Find the most simple circut and fix that. The lights are a good one.

[87MH]

Originally Posted by GlenCoombe

....Guy, I thought the isolator also joined the batteries for starting purposes? Maybe it's just a delusion....

Glen:

The isolator only "joins" the two battery banks for charging purposes - it's a safety measure to insure that if you drain the coach batteries the chassis battery will not be pulled down at the same time.

On most 345's there is a switch in the glove compartment - on the top or "ceiling" of the compartment - by momentarily holding this switch "on" you engage a relay that "joins" the coach and chassis battery banks...thus allowing a "boost" for starting the engine.

I have not had to use this switch since I spent the bucks on a "good" starter for the 454.

I do not think this booster switch has anything to do with CK's problems...JohnHD gave some good advice - start at the battery and check and eliminate from the problematic path each wire and connection from there (both positive and negative) until you find the point of "no voltage" - it may take a while, but it is the only logical way of trouble shooting an open wiring circuit....the fact that CK has voltage to his voltage indicator should narrow down the search a bit - it does sound as if the problem is in the wiring from the battery/alternator co-joining to the fuse block, or in the fuse block itself....

After the problem is found maybe CK will kick back with a cool one and ponder Sherlock Holme's words .....

"Eliminatary (sic) my dear Chaplain."

[ralley]

Originally Posted by 87MH

Glen:

The isolator only "joins" the two battery banks for charging purposes - it's a safety measure to insure that if you drain the coach batteries the chassis battery will not be pulled down at the same time.

On most 345's there is a switch in the glove compartment - on the top or "ceiling" of the compartment - by momentarily holding this switch "on" you engage a relay that "joins" the coach and chassis battery banks...thus allowing a "boost" for starting the engine.

I have not had to use this switch since I spent the bucks on a "good" starter for the 454.

I do not think this booster switch has anything to do with CK's problems...JohnHD gave some good advice - start at the battery and check and eliminate from the problematic path each wire and connection from there (both positive and negative) until you find the point of "no voltage" - it may take a while, but it is the only logical way of trouble shooting an open wiring circuit....the fact that CK has voltage to his voltage indicator should narrow down the search a bit - it does sound as if the problem is in the wiring from the battery/alternator co-joining to the fuse block, or in the fuse block itself....

After the problem is found maybe CK will kick back with a cool one and ponder Sherlock Holme's words .....

"Eliminatary (sic) my dear Chaplain."

With regard to the paddle switch in the glove box which joins battery banks in the 345. Ditto the 350, (and perhaps the 360 and 370??). The relay is on the back side of the battery box, facing the frame--it slides in and out with the box. If clean and with fully charged batteries, I can hear my relay kick in from the driver's seat. Recently one of the bolts holding a wire on mine worked a bit loose--which is how I found it.

[ticki2]

From the pictures shown , the left lug on the isolator should be from vehicle battery . The center lug should go to the alternator , and the right lug go to charge the house battery .The smaller wire on the left lug looks like it was added to supply something aftermarket ( should be hot ) which also means something in the coach is presently working , unless you have lost chassis ground.
The connection to the left of the isolator I believe is a simple juction block and not a curcuit breaker as thought before , typical of GM . The heavy center wire going to the alternator is also a typical place for GM to put an inline fusable link , it may be hidden under some of the wire loom . You had mentioned before that you had not found any fusable links , this would be highly unusual in any pre '89 product .

As mentioned previously , a good start would be to by-pass the isolator . Remove the wire from the right side of the junction block and the left side of the isolator (remove ground from battery first) . Then take wire from center lug of isolator and connect to right side of junction block.
This should give you power to the alternator and hopefully the fuse block . If it doen't you have a bad wire from the juction block to the alternator . If it does you have a bad isolator .

This stuff is frustrating enough on a good day , hope your'e feeling better . Good luck

[Chaplain Kent]

Originally Posted by garry

John HD has outlined a good way to start with the basics of troubleshooting an open wire, you can also use an ohm meter.I think you will have to start with just one item (forget the key) pick something that should have power all the time like a headlight or parking light turn the light switch on and go from there. When you find the problem why the lights don’t work everything else will fall into place.

Garry

(had to edit to make it readable)

This has been done. Each and every circuit, wire, strand, and conductuctible dust has been traced to its source. We even tore open the steering column. No problems have been noted. I am going to by-pass the isolator next.

[ralley]

This makes sense, except that I am under the delusion that the left hand post on the isolator is the starting/alternator/lights/ horn and all that other stuff circuit, and the RH post on the isolator is the house batteries. It makes little sense to me that your problem would be in the house battery circuit, but--nothing ventured, nothing gained.

I am beginnning to think that there is not one problem, but a series of problems. I still think that there is a ground problem.

I am reminded of the comment of Thomas Edison when asked about his years of failure to find a suitable filament for a light bulb. He said-- Ï haven't failed. I just know 10,000 things that don't work!!

R

[Chaplain Kent]

Chummy Runs!
I by-passed the battery isolator, honked the horn and it blared away, turned the ignition key and the engine started right up and asked what took me so long? Tried the turn signals and I even had them wired correctly. Looked at the tach and it was working. The fuel gauge registered fuel, the oil pressure gauge had oil pressure showing and the lights worked.
Why did the isolator burn out? I really don't care as long as it does not happen again. Tomorrow I will search for a new isolator. We have a plethora of marine shops around here so I should be able to find one.
Thanks to everyone who helped on this one. I can not say how much I appreciate the support and advice.
Now if anyone needs to know where a wire goes or what a particular wire does I think I just might know. I plan to take some pictures of the wiring mess before we start to clean it up.
Thanks Guys!!!

[john hd]

good for you!

john

[swebster]

Yahoo!!!!!

[ralley]

O, Lord, for what we are about to receive, let us truly be thankful!!

Ch Kent: you will need to know what the MAX amperage your alternator puts out in order to buy a correctly sized isolator. The only variable is the diodes' ability to withstand higher amperages--so higher rated diodes are bigger and therefore higher rated isolators are bigger (to disipate more heat) and more expensive. I forget the rule of thumb for this--perhaps someone else has it at hand.

I don't know about you--but we all feel much better. You will pardon my saying so, but I never thought Chummy would be happy as a flower pot!!

[PeterH-350LE]

I would like to make a prediction:
Once the new Isolator is in place, hooked up just like it was before, Chummy will not have power to the main fuse block.
The current Isolator is probably not even defective.
All what the good Chaplain did with by-passing the Isolator, is providing an alternate source to the main fuse block via the alternator.
This can not be a permanent solution, since the MH will loose charging ability to the coach battery bank.
All of this points to the very first wire from the starter solenoid to a junction block to be bad due to a blown fusible link.

[ralley]

Originally Posted by PeterH-79MH

I would like to make a prediction:
Once the new Isolator is in place, hooked up just like it was before, Chummy will not have power to the main fuse block.
The current Isolator is probably not even defective.
All what the good Chaplain did with by-passing the Isolator, is providing an alternate source to the main fuse block via the alternator.
This can not be a permanent solution, since the MH will loose charging ability to the coach battery bank.
All of this points to the very first wire from the starter solenoid to a junction block to be bad due to a blown fusible link.

Ok, fair enough, and easy to check.

If CH Kent dismounts the battery isolator and checks the resistance of each diode, they should be the same if the unit is good. If they are, then PeterH may be on to something. You could further test his idea with a jumper run directly from the solenoid to the remounted, good battery isolator, or the various junction blocks wired to it. If the jumper makes the system work.............At least I think I have understood him correctly

R

[3Ms75Argosy]

On my Chevy Astro - the positive to the starter was a fusible link....WITHIN THE CABLE ITSELF. The cable was made to "melt" under the insulation jacket - there reallly was no way to see it. IF the new isolator doesn't work, I think testing the resistence of the wires may be the ticket.
Marc