What could this be? Intermittent 12 volt power while driving

[D. Wendal Attig]

just had a new transfer switch installed yesterday. (previous switch had burned contacts) While all systems running through the new transfer switch seemed  a "go" after picking up the coach, I have acquired a new "condition" .

While driving across town, I would get and intermittent indication of zero electrical power. At this point, the volt meter would bounce to no indication at all, then back to the 13+volt normal position and the dash air would respond in kind to the action of the volt meter, returning to full operation along with the renewed normal voltage indication.

After reaching my destination, I turned the coach off, but upon returning it would not initially start: no starter solenoid sounds, however, all gauges but the volt meter were operational. Lights would come on, 12 volt accessories outlets were operational. Just no start.

The mechanic assured me by phone that they had only worked on the AC system, which should have had nothing to do with DC voltage, but had not encountered my issue before.

While on the phone with my roadside assistance rep to arrange a tow, I tried to start it again, and wa-la---it started. No grinding, no struggle, but a solid start instantly.

Called the mechanic again, who ask me about batteries (all new in March of this year) mentioned a possible alternator or starter issue, or starter switch.

Upon shutting down after arrival at the RV park, the coach would not start again.

We have been on shore power for about a month, with occasional start-ups to keep lubricants in  place, without any incidents. Our return trip from Mississippi (1100 miles) produced no such symptoms. Only thing new is internal surge protector (no problems) and the new transfer switch.

Your thoughts or suggestions on what advice I might share when/if I can get it back to the shop this morning are appreciated.

Thanks,
D.

PS, one other noticeable difference following the transfer switch installation is that the surge protector waits only a few seconds instead of the original 90 seconds or so, to check power quality before allowing the source to pass through to the coach. hmmmm

[Keith Moffett Co-Admin]

A failure of the diodes in the alternator can produce similar results and would affect the systems you mention.
A failure of the starter might produce the non start intermittantly but I dont see it causing the rest of the dash fluctuations.  I have however seen the blow by pipe too close to the starter and the residue gumms up the connections causing an intermittant failure.
I would check the output from the alternator.  If I could get the engine to start I would put a volt meter on the chassis batteries.  13.8 volts or better with the engine running.  If the alternator passes check connections on the starter and be sure they are clean.  The starter may need to be pulled and cleaned.

[Jim Houghton]

A faulty ignition switch can also cause your issues.

[Edward Buker]

D,

The issue I would start on is the while driving across town, no power with the air and dash dying. There are only a few things that can cause that on your coach and it has nothing to do with the transfer switch so I think your tech is right.

The primary cause of that is likely to be the solenoid at the bottom of the copper buss bars in the electrical bay. I would buy a new one and change that out. The contactors in them arc and erode and they fail. The ignition switch is also a possibility but not as likely to be an issue. The ignition switch powers the solenoid. There can be a wiring issue but that is unlikely compared to the make and break contacting components.

Intermittent cranking may be part of the dying issue but it can also be a battery issue of marginal current and voltage. Your batteries should be sitting while parked with some kind of charge taking place, and the terminals need to be tight and clean. If you get a non start due to a no cranking condition again, hold down the switch that couples the battery banks for 30 seconds and while holding it down crank again. If it starts then it is likely a voltage/current issue from the starting bank that you overcame by providing extra capacity from the house bank.

Check the voltage while sitting plugged in on the starting bank to see if it is in the 12.9  to 13.6V range maintaining charge while sitting. Solve the voltage dying issue first which is likely the solenoid and see if the cranking issue goes away. Hope this helps.

Ed

[Bob Jae]

I agree with ED and had the same symptoms on my coach.  I bought a ST-85 continuous duty solenoid from NAPA and ordered a spare from Amazon after I knew it fixed the problem.  When mine would not start I would get no dash lights or meter movement when I turned the ignition switch to on.  I will try to attach some pictures.  In the one I took the old part apart and you can see the burned contacts.

[Edward Buker]

You can also use this unit to eliminate the mechanical contacts all together. I have installed one of these in my electrical bay and do not worry about this anymore.

http://www.westmarine.com/buy/cole-hersee--ultra-reliable-electronic-solenoid--2674489

Later Ed

[Joel Ashley]

I have to echo Ed's solution, although I've not had to do it yet myself.  This topic was broached some years back.  It was obvious to me from prior experience over 30+ years with relays and solenoids that can leave you stranded and scratching your head, that when mine needs replacing I'll go with the electronic version.  Yeah it's a lot more expensive than the old Ford solenoid style whose build quality varies considerably enough as it is, but the electronic is one and done.  That particular solenoid has just too many things depending on it to go cheap.  Just look at the lineup of devices downstream of it on those busses above it.

Joel

[D. Wendal Attig]

Gentlemen,

The batteries are showing 13.7 volts on the CMP. They are new as of April (all batteries were replaced) All terminals are clean and tight. NAPA was closed by the time I got there today, so I visited O'Reilly, where they sold me an S55 by BWD, which looks identical to the Cole Hersee, currently installed. Don't know if this cross references the NAPA S58.

Oreilly's did caution me to be sure the ohm value was the same before installing, but I don't know what that/those reading(s) should be.

Markings on the BWD Unit say, 12v followed by 1507. Instructions such as they are in the packaging refer to this being a new design.

Viewing the unit from the top as it would be mounted, the instructions identify the large terminal at 9:00 to be connected to the + terminal on the main battery. Large terminal at the 3:00 position  should be connected to the + terminal on the auxiliary battery. The smaller post  at the 7:00 position calls for a connection to ground, and the smaller post at 5:00 should connect to the "accessory" post on the ignition switch.

Does anyone know if these parts are interchangeable?

Do the connections identified look right?

If I install this, will it be "Hot" before the ignition switch is activated?

As always, your input is extremely valuable, and I appreciate it so much.

Thanks,
D.




 

[Edward Buker]

D,

That unit should be fine. Do not worry about the ohm measurement, your old one may be shot and give higher ohms anyway.

You should have a DC voltmeter or at least a 12V test light. Basically you will verify with the ignition switch on, which small wire has 12v on it and make a little diagram or label it. Then turn off the chassis battery switch if you have one, if not disconnect the 12V + chassis battery leads. Verify that the left copper buss bar has 0V on it by measuring from the copper buss to a ground point either in the electrical bay or metal frame around the door. The two larger posts that are tied to the buss bar wires will be connected just like they are now on the old unit.

One of the two smaller wires that go to the small posts on the old unit, the one that had 12V on with ignition on, will go to the 5:00 post and 7:00 to ground which is the remaining small wire. That should do it. Reconnect the chassis battery and test it. The right copper buss measured to ground should toggle on and off of 12V with the ignition switch on and off.

You do not install this hot and the connections should be fine. Do not worry about larger wire post connection verbage, connect them just like the old one was.

Later Ed

[D. Wendal Attig]

Thanks, I do have a voltmeter and will test as you suggest.

As to actually removing the battery wiring, I am wondering if the "coach power" switch just inside the entry door will accomplish the same?

When you suggest turn the ignition switch on, I am guessing that just means to the initial position just prior to actually starting the coach, Yes? No?

[Edward Buker]

D,

Basically you want the left and right copper buss without 12V on them by whatever means it takes. I think that switch by the coach entry is just the house side, but you can measure at the buss and see.

Yes to the question about the ignition switch, no need to start it, just the key in the ignition on position where the accessories like the dash fan and gauges start to come on. If the dash fan comes on then it is working.

The chassis batteries are 12V, house are 6V with three caps vs the typical rectangular covers over the cells. If you do not have a manual switch that disconnects the chassis batteries, then you need to remove the heavy red wire that leads from the battery post to the coach. Then verify that the left buss in the electrical bay is no longer at 12V. You can use a zip tie to hold the red wire you removed, temporarily tying the wire it to some other insulated battery wire, so the metal end is kept securely off of a terminal point. The screw lugs are typically embedded in lead which is soft. You want the terminals tight but there is a limit as to how far to go in tightening these. Good and snug is enough...

Later Ed

[D. Wendal Attig]

Ed,

Identified the small wire with 12v with ignition switch on, Then disconnected all + (Red) cables from starter batteries and have them held well out of the way with zip ties. However, I still get a 12v reading on the large red cable and the left battery buss---not zero as you noted it should be. This leads me to believe it is still hot, but there is no connection now feeding it.

Also, the small wires as currently installed will swap to the opposite terminals according to the diagram that came with the unit. Should I also reverse the position of the small jumper component between those 5:00 and 7:00 terminals?

Update: I installed the new solenoid, matching the wiring to the ground and ignition small posts as outlined above. I also installed the bridge jumper (between the small posts) Then reconnected the positive (red) battery cables on the starter batteries. Then I tested the power post and left buss and both showed 13.6 VDC.

Next I turned on the ignition key and came back to the wiring bay to see how the voltage would read. The component was making an intermittent single popping sound. I turned the key off and came out to the wiring bay again, to see the bridge component exploded and the interior connection of the component melting. Something's not cool here---literally. I did NOT try to start the engine at that point.

I have tried to be as detailed as possible, so hopefully you can recognize any misguided steps.

Please Advise

 
Thanks,
D.

[Edward Buker]

D,

Not sure what happened here. It could have been a defective unit and shorted inside. The upper large wires are just a switch that is either on or off based on the solenoid coil seeing power from the ignition switch. So you have a magnetic coil powered on or off pulling the contacts closed, there is spring tension to open them back up. The larger red wires cannot be at fault here unless they contacted the body of the metal solenoid along with the insulated stud. I think maybe the ground was wrong on the small terminals. I would have thought they would be isolated.

If you have an echo charger pull the fuses while you work on it, something was still bringing power to the 12V chassis side. If you find someone with an ohm meter/voltmeter and can help. You can pretest the solenoid with a couple of small wires and assure that it will be connected properly and is not defective. I assume the battery connections in the rear of the coach were puled and put back as they were. Hope this helps.

Later Ed

[Edward Buker]

D,

We have been away helping a friend all day and just got back and reread your note. One thing I just noticed in your note, "installed the bridged jumper" ......that item is usually a diode that has to be installed in a certain direction across the smaller wire terminals.

There is an end that has a bar printed on it, sometimes it is an arrowhead and a bar. Whichever of the smaller terminals has the +12V connection from the ignition switch connected to it becomes the connection point for the end of that "jumper" with a bar on it. This is actually a diode. I'm not completely sure if you switched the small terminal wiring and not the diode direction. If the diode was installed the wrong way it would have shorted and probably conducted a good amount of current. You should get a new one and install it  with the new solenoid, these would be fine.

https://www.amazon.com/uxcell%C2%AE-1N5408-Silicon-Rectifier-Diodes/dp/B00SUVR5LI/ref=sr_1_2?ie=UTF8&qid=1468885783&sr=8-2&keywords=1n5408+diode

In order for the problem you had to occur there had to be a shorting condition somewhere in what you done, so try and sort that out before making any new connections. Get some help if needed...

Later Ed

[D. Wendal Attig]

Ed,
I believe you hit the nail on the head. Just as you thought, I had not reversed the diode direction yesterday to match the small terminal orientation, which no doubt caused the problem.

Had the solenoid tested tonight at Oreillys and it checked out fine. Got the identical diode at Radio Shack. All is installed, but it's too late to start and run the coach in the RV Park tonight, but will test it first thing Tuesday morning and let you know what happens.