That relay by the battery...

[pconroy]

I think someone posted a while ago that they had to change it. I've noticed that when the engine's running, the alternator is not charging the house battery anymore. Or it's intermittent.


Did I recall the solution correctly? Did someone say replacing that relay buried in the battery compartment was the fix?


thanks!!

[craigav]

Hi PConroy, Yours may be different, however this is schematic is very similar to mine even though the diagram indicates this is for a 2013. In any case, if you look at the upper right side of the document you will see a "100 A Solenoid" (relay) which is the relay. Mine is under the hood, on the back firewall, almost directly in front of the steering wheel. Yours may be there as well.

If you follow the line in the schematic going to the left of the 100A Solenoid and to the right going to the fuse block you will also see a '80A MINI BREAKER" listed, one in the front and one in the back. However, I don't recall seeing them to know where their exact location would be. I suspect the front one is near the front relay and the rear one is in or near the "COACH" battery compartment. I would check the breakers first if you see them and check if they have a reset button on them.

This schematic doesn't indicate a relay near the coach battery except the one for the "Battery Disconnect". Again, yours could be different, however Jayco tends to be fairly consistent with how they build things.

(I suspect the breakers auto-reset and don't have a reset button) ~CA

[pconroy]

Thank you!


It looks like the line I have in yellow is the one to follow and debug! Like I said - it's intermittent which could certainly indicate a failing solenoid. Looks like there are several in the path to debug.


Any suggestions for how to debug a solenoid?

[craigav]

The line I marked with "red" would also be suspect. This wire should be hot with the key on to trigger the relay. If it had a bad connection, then that would cause the relay not to engage. I seem to remember I had to clean the wire connections on that relay years back as mine wasn't working reliably either.

One thought of something you could check is to have someone turn the key on and off while you listen at the relay to hear if the relay engages and disengages (should be a noticeable click sound), and this relay is also the one that connects to the button on the lower left dash, which should also click the relay when pushed. ~CA

[craigav]

After looking at the complete schematic better, it doesn't show that wire going to the key switch, in fact it doesn't even show the key switch (unless I am missing it). However, on mine the relay does click when I turn the ignition key switch on, which causes my steps to close (which is where my red highlighted wire actually goes). What I see in this schematic is not exactly how mine or yours may be wired as I don't see any circuit that closes the relay except the "AUX START" button, however I know my relay does indeed click and close with the key on. Also, if it didn't engage then there is not other circuit to charge the coach battery. ~CA

[craigav]

Highlighted here in yellow is where the key switch (IGN) engages the relay, the "key on" power goes to the "Aux Start SWitch". I replaced my radio years back and noticed that Jayco did a poor job with their wiring in and around the "AUX START" switch. In any case, I would make sure the relay clicks with ignition on as well as when the AUX Start button is pushed. The relay isn't all that special or expensive and I would consider replacing it if the problems continue. Intermittent issues can be a challenge to figure out for sure. ~CA

[pconroy]

Thanks a million for those!


I found an earlier post by JimD showing how he debugged and replaced it.

Engine off - both lugs showed about 12.6V, one a smidge higher. I suspected Top Lug was house battery, bottom lug to chassis battery.
Engine on - top lug still at 12.6V, bottom lug now at 14.7V. Since they're not the same voltages with engine on, either solenoid is bad or it's not triggering.

I'll flip the ignition on and see if I can hear the click.

[craigav]

Good to know, I suspect with enough time that these relays will fail, and in any case I would be interested into knowing what you find as I suspect it is simply a matter of time that I and others will have this issue. ~CA

[pconroy]

Any suggestions on how to check for the "trigger" signal? Would that be voltage or current?

[craigav]

According to what I see on the schematic, the Orange wire going to the relay is the trigger wire and with that, you should see the voltage on that wire when either the key switch is on, or when the aux start button is pushed, and no voltage on that wire when the key switch is off and the aux start button is not pushed. You could use a short jump wire from either the top or bottom heavier 12v connections (the ones you mentioned earlier) and connect the jumper wire (temporarily) from there to where the orange solenoid wire connects and that should make a click (make sure you have a good connection). If the solenoid clicks, then the trigger wire(s) would be suspect, if that doesn't click the solenoid then the solenoid would be suspect. FYI, I have used a jumper here simply to allow the converter\charger to charge the engine battery when I am plugged into shore power. However doing that makes my steps go up so I don't do that all the time (they come back down when I open the door though). ~CA

[JimD]

Originally Posted by pconroy

Thanks a million for those!


I found an earlier post by JimD showing how he debugged and replaced it.

Engine off - both lugs showed about 12.6V, one a smidge higher. I suspected Top Lug was house battery, bottom lug to chassis battery.
Engine on - top lug still at 12.6V, bottom lug now at 14.7V. Since they're not the same voltages with engine on, either solenoid is bad or it's not triggering.

I'll flip the ignition on and see if I can hear the click.

Hey, I resemble that remark. You beat me to this. By the way, I absolutely love the color of your meter! My old Fluke yellow has seen its better day.

[craigav]

I just took a look at mine. Notice how poor the connections are from Jayco, (although mine is 10 years old now). The test lead you see in my pic on the left side connection, that terminal should have no voltage with the key off and the aux start button not pushed. It should have voltage when the key is on or the aux start button is pushed. If you don't get voltage, you can take any jumper wire, even your meter cable should work and manually engage the solenoid by taking the 12v from the circuit breaker (mine has no cover and is to the right of the solenoid) and jump that 12v power to where the orange wire connects as in my photo and you should hear a click. I just verified that on mine. Also, this is what I was mentioning that I do sometimes to allow the converter\charger to charge\maintain the engine starting battery (but only when needed). ~CA

[craigav]

BTW, I suspect but didn't check, the key likely has to be all the way on in the engine "run" position, not in the first click acc position.

[craigav]

Originally Posted by JimD

Hey, I resemble that remark. You beat me to this. By the way, I absolutely love the color of your meter! My old Fluke yellow has seen its better day.

Jim is here now! I bet he can add a lot more detail. FYI, I took the courses and passed my Electronic Technician certification tests back in 1980, however I took a different career path in life. I should check but I think my certification allowed for me to be a journeyman and if I am not mistaken those certifications back at that time never expire like they do now. Not that it matters now that I am retired. I still play around and fix old receivers more for a hobby than anything else and enjoy electronics and related things. ~CA

[JimD]

Here is an excerpt from a document I am putting together to help RVers troubleshoot their systems:

House Battery Charging From Vehicle’s Alternator

To verify that your house battery is being charged from the engine’s alternator just put your test meter on the house battery and start the engine. If the voltage increases, you are charging. If no voltage increase you will need to locate the charge relay (sometimes called solenoid). It may be mounted in the engine compartment on the firewall.

Attached are 2 examples of the standard relay which is not bi-directional. Both are troubleshot in the same manner. The 2 small terminals are the “primary” side of the relay and the 2 large terminals are the “secondary” side. When 12 volts is applied to the small terminals it energizes a heavy contact inside the assembly which connects the 2 large terminals together.

One large terminal will be connected to your chassis battery and the other large terminal will be connected to the house battery. You can easily measure each large battery connection with your meter. Connect the black meter lead to a metal ground, bare metal, screw, whatever and then touch each large connector with the other meter lead. Each large connector should show a slightly different voltage as long as the relay isn’t energized. When energized, both large terminals will read the same voltage.

If you suspect the relay is bad, first measure across the 2 small terminals with the engine running. It should read 12 volts. If it doesn’t there is a problem with the feed to those terminals. One terminal will be connected to chassis ground (metal) and the other small terminal will receive a 12 volt signal from the ignition circuitry.

If there is 12 volts across the 2 small terminals but the voltage at each large terminal is different (measured to metal vehicle ground), the relay is bad.

You can also energize the relay manually without the engine running. First disconnect the wire from the small terminal that comes from the ignition circuit. The other small connector will be ground. Then simply jumper either large terminal to the small terminal that you just removed the wire from. You are simply supplying the 12 volt signal to energize the relay. Usually you can hear it engage.

[craigav]

As another thought while I am thoughting, I have seen relays that actually would click but didn't carry the current. That is because the internal contacts (or possibly the external connections) have gone bad. What you would want to do is jumper the relay so it is on (or have someone press the aux start button as long as that makes the click in the relay) and then measure the two voltages as you did earlier. In this case you may need the engine running to bring up the chassis voltage otherwise if the two batteries are at the same voltage then the results could be misleading. In any case, once the relay is engaged the same voltage should be measured on both the top and bottom larger relay terminals, if not then the relay likely is bad (the contacts inside or a poor connection of the larger cables). In fact, in such a case I would consider first using a wire brush and clean up the cables and posts they connect to (especially if they look like mine look). That is what I need to do soon anyway, and then a bit of dielectric grease would protect them for a long time to come. ~CA

[craigav]

Originally Posted by JimD

Here is an excerpt from a document I am putting together to help RVers troubleshoot their systems:

House Battery Charging From Vehicle’s Alternator

To verify that your house battery is being charged from the engine’s alternator just put your test meter on the house battery and start the engine. If the voltage increases, you are charging. If no voltage increase you will need to locate the charge relay (sometimes called solenoid). It may be mounted in the engine compartment on the firewall.

Attached are 2 examples of the standard relay which is not bi-directional. Both are troubleshot in the same manner. The 2 small terminals are the “primary” side of the relay and the 2 large terminals are the “secondary” side. When 12 volts is applied to the small terminals it energizes a heavy contact inside the assembly which connects the 2 large terminals together.

One large terminal will be connected to your chassis battery and the other large terminal will be connected to the house battery. You can easily measure each large battery connection with your meter. Connect the black meter lead to a metal ground, bare metal, screw, whatever and then touch each large connector with the other meter lead. Each large connector should show a slightly different voltage as long as the relay isn’t energized. When energized, both large terminals will read the same voltage.

If you suspect the relay is bad, first measure across the 2 small terminals with the engine running. It should read 12 volts. If it doesn’t there is a problem with the feed to those terminals. One terminal will be connected to chassis ground (metal) and the other small terminal will receive a 12 volt signal from the ignition circuitry.

If there is 12 volts across the 2 small terminals but the voltage at each large terminal is different (measured to metal vehicle ground), the relay is bad.

You can also energize the relay manually without the engine running. First disconnect the wire from the small terminal that comes from the ignition circuit. The other small connector will be ground. Then simply jumper either large terminal to the small terminal that you just removed the wire from. You are simply supplying the 12 volt signal to energize the relay. Usually you can hear it engage.

Hi Jim, just for my understanding and not really relevant to the testing PConroy is doing, you mentioned that the relay(s) in your document are "standard relay which is not bi-directional". Shouldn't that read "standard relay which is bi-directional" as the current can flow either way, and the relay is commonly used to allow the house battery to obtain current from the engine battery if needed, as well as the opposite when needed. Wouldn't a directional relay be solid state and/or use a diode? Anyway, your document is very informative and very helpful to the issue, and I am sure it will be very helpful for everyone. Many Thanks, CA

[pconroy]

You guys are awesome!


A couple of hours ago, I went back out with the multimeter to check the trigger. As luck would have it, it decided to work.


On my 2016, flipping the ignition on was enough to hear the 'clunk' and the two big lugs, as well as the orange lead were showing 12V power.


Starting the engine, and sure enough - and all three connectors went up to 14V.


So, I've plunked a replacement solenoid in my Amazon cart.
I'm thinking it's just a matter of time before it croaks.


They're ranging from $18 to $36.
I found an exact replacement (White Rodgers 120-901) for $23 - but they want $20 for shipping. So I'll go with Amazon.


Thanks all for making this group wonderful!

[craigav]

Good Deal, and not to get off topic, but on a related aspect. My RV engine battery will discharge with enough time even when the RV is plugged in. By design the RV converter/charger doesn't charge the engine battery.

I am not sure what is pulling the engine battery down (perhaps the radio), however I plan to install this switch in place of the momentary push-button AUX Start switch. Doing so is similar to what I stating I was doing with the jumper wire. This switch when the cover is closed will be similar to the push button switch not pushed but will allow me to keep it on when desired which would allow the coach charging converter to keep the engine battery charged. Either this, or I find out what is pulling the engine battery down, and whatever it is, it isn't a lot of current because it takes weeks before the engine battery goes too low to start the engine.

Just another project for me when time allows. FYI, the relay is designed to be continuous on whenever needed, so doing this would not be a relay issue but perhaps Jim has some thoughts with my plan that I should consider further.

Anyway, good deal for you, I think replacing the relay is a great plan seeing that it is not overly costly to do so and has a high likelihood of being the issue. ~CA

[JimD]

Originally Posted by craigav

Hi Jim, just for my understanding and not really relevant to the testing PConroy is doing, you mentioned that the relay(s) in your document are "standard relay which is not bi-directional". Shouldn't that read "standard relay which is bi-directional" as the current can flow either way, and the relay is commonly used to allow the house battery to obtain current from the engine battery if needed, as well as the opposite when needed. Wouldn't a directional relay be solid state and/or use a diode? Anyway, your document is very informative and very helpful to the issue, and I am sure it will be very helpful for everyone. Many Thanks, CA

The reason I called it non bi-directional is that I found out, thanks to this forum, that some RVs (newer) have relays that are called bi-directional. They actually allow charging of the chassis battery from the converter. Who would have known. Here is a link to some info on it.

https://www.intellitec.com/wp-conten...-00362-100.pdf

Many years ago I had a solid state battery thing in my old truck/camper. It looked like some diodes on a big heat sink. It only charged the camper battery from the alternator.