Has anyone changed A Temp Sensor

[DCTENT]

I have been told To replace My Temp Sensor On My 2008 Dynasty, As My Big Boy Will not open Up to Charge Batteries.
Well guess Ya know, That is IMPOSSIBLE, To remove Old line as it runs from Rear battery Comp To front of Coach, Even If I take it to a Monaco Shop (IF YOU CAN FIND ONE ANYMORE), I don't believe they could string this thru frame & whatever else would be in the way.
ANY IDEAS?????

[Rex]

Dave, I have been told by many owners that there are spare wires up front that terminate somewhere in the rear. Mind you I have looked for these on my Diplomat and never found any, but perhaps your coach has them.

The other option is the wire conduit under the coach. On mine there was a spare 2" conduit that ran from just above the tie-rod end to the rear of the coach just above the transmission. It was hard to see so look up front behind the axle and follow the wiring you see running along the frame rail to where it disappears. Hopefully you will also find a spare conduit. If you do, run more wire than you need so you have spares if and when needed.

[YC1]

What temp sensor and what does that have to do with the big boy solenoid? I'm confused.

[DCTENT]

First Year I Had Coach, I Had It Plugged into 50 AMP Inside My Garage, I Live In Minnesota where it gets below Zero for Days & Weeks. One day during inspection, (ALL) my batteries were frozen. I Could Not at that time understand why, I Replaced All with AGM's, They were fine during following Summer, Then Last Winter after being plugged into 50 AMP (All the time its not in use), My Engine Batts discharged.... After performing Test VIA Monaco Support, He informed Me My Big Boy was not opening, causing My Engine Batts To Not Charge.. (THATS WHAT A BIG BOY DOES) I Guess.
I purchased a New Temp sensor which is a 45' Telephone Cord that has sensor attached to Engine Batts & Runs From Rear of Coach to Front Compartment Where it makes connection.
Am I the only one that has this?, Seems unlikely,

[YC1]

Ok, the Big Boy actually "closes" to bring both sets of batteries together. It should be very warm to the touch if not hot. Take a picture of the big boy and post it here to be sure we are on the same page. Troubleshooting this is easy. The solenoid is a known problem. I have replaced mine twice on my 08.

[Mike Canter]

The Big Boy only closes to charge the chassis batteries after the house batteries have been charged up to 13.1 volts or greater. If the charger is not set up correctly or the house batteries have a problem it will never charge the chassis batteries. I have two battery temp sensors and they both are attached to my house batteries. One is for the solar charge and one is for the inverter/charger. Where does this temp sensor you are installing go to?

[YC1]

The big boy relay will close when there is an available charge voltage above a certain limit. It does not charge one bank and THEN switch to the other or bring both online. For example, engine running with alternator charging, the BIRD will pull the solenoid in no matter the charge state. Or, if the generator or shoreline is providing power then the coach batteries will have a higher voltage and that will cause the relay to pull in via the BIRD. Or, you have solar and the panel is puttiing out enough then the relay will get pulled in under those condtions as well.

The relay is notorious for failing. I provided a picture of a failed on in my post above. They can be easily rebuilt if you are handy with a soldering gun but they cost less than $50 for a good replacement.

This charging circuit is a big mystery to a lot of folks and took some studying to get to the heart of it. Not all rv's have it of course and not even all Monaco's or HR's have them. The temp sensors should be telling the charger if the batteries get hot and would turn the charge down. There is also a temperature sensor in the charger compartment of mine that will turn a fan on when it gets too hot for the charger.

[DCTENT]

Mike:
The Sensor is attached to side Of Engine Batts On end Of a Telephone Cord with Two Wires & Goes To Front Comp Thru An Enclosed Loop & Has a Telephone Connector To Magnum on other end. I was Told By Monaco Tech This has to be replaced. Which I find NO way of Replacing without tearing half the Coach apart.
I Just took Pics & am trying to figure out how to attach them to this Forum.
My Big Boy as we speak is feeling Hot According To Monaco when Temp outside drops down In Minnesota weather this Sensor is suppose to open & Close to Keep Engine Batts Up, But It does Not in cold weather.
I Just went out To Garage, AGS Says FULL CHG at 12.7V, OA, Tech informed Me that it has to Chg at leat 13.2 to Chg Engine Batts. So does this mean my Engine Batts are not getting Charge?.
At times when Im at Coach it will show Charging at 13 Plus Volts, I don't understand.

[Rex]

Dave I also have a battery sensor that is connected to my batteries. The other end is connected to a jack on the Inverter and the Inverter uses the temp to determine if the batteries are being overcharged and thus reduce the current a bit.

I have not heard of a battery sensor that connects to anything on the front of the coach. If you have an Alladen system, your temp sensor may be connected to it up front.

[DCTENT]

Too Rex!!!
I Have same that you stated above, I should have not stated front of Coach, It actually Goes From Batts To Magnum In Front Compartment same as yours, Any idea how this can be replaced? Per Monaco Tech.

[wa8yxm]

If you don't want to run a 50 foot cable.. Can you just cut and splice the new sensor to the old cable? I mean telephone wire is only 4 wires, I think the sensor uses just 2 of 'em, and they make punch down splice blocks for that kind of wire that makes it super easy.

Or you could install an old style telephone modular jack (the one with the 4 pins in a square) and plug in the battery compartment.. That would be easier, though not as reliable.

[moisheh]

dctent: Where is your Magnum charger/inverter located? On our Dynasty it is in one of the bay compartments. When you say front surely it is not in the front run compartment beneath the driver? If indeed you need to install a new cord it cannot be that hard to run a wire underneath. I had run wires from the front right to the trailer hitch area for our US Gear system. There are lots of other wire looms underneath that would hold that small wire via wire ties.

[Mike Canter]

YC1, I am not sure I understand what you are saying. The B.I.R.D system first charges the house batteries to a specfic voltage which is either 13.1 volts for 2.5 minutes. Then once that voltage is reached then the Big Boy is closed so that the chassis batteries are then charged. If the chassis batteries drop below 12.6 volts for one minute then the Big Boy will open up so the batteries are isolated and the chassis will not run down the houses and visa versa. Again, if for some reason those house batteries cannot be charged to that specified voltage then the chassis batteries will never be charged and will go dead. This problem occurs a lot on people that install AGM house batteries and switch their inverter charger to AGM mode. They just will not get to the specified voltage. Switching the charger back to lead acid will then charge the AGM above that specified voltage and the Big Boy will close and charge the other batteries.

[Rex]

Dave first I would determine IF the cable is bad. It should be a 4-wire flat telephone type cable. If you have a clear plastic plug on one end, you should see the wires - red - green - black - yellow.

If you cut the cable near the batteries so you can access the wires, test them to see if they have continuity. Just short the red to green and see if you can read the short with an Ohm meter on the other end. Then short the black to yellow and do the same test. If you have continuity, the cable is OK.

You can get a kit at Lowe's or Home Depot with a tool to put a new plug on the end you had to cut. You can also get a straight through jack that a plug goes into each end at Lowe's.

If the cable is good, just cut the cable off the new battery temp sensor and put a plug on it - use the straight through jack - plug the old cable into it and the sensor is connected.

If the cable is bad - well see my post above where I talk about a spare conduit under the coach and look for that.