Harvey Babb

I stand by my post. If you connect the resistor and an LED and apply 120 volts the LED will be instantly destroyed by excess reverse voltage. Putting a diode in series with the LED-resistor combo will protect the LED from high reverse voltage allowing it to operate safely, as would connecting the LED and diode in reverse parallel so that reverse voltage is shunted around the LED. Yes, the resistor will dissipate quite a bit of power and will need to be sized appropriately. I did not (and would not) suggest that this was a good solution; I only wanted to point out using the LED-resistor combo would destroy the LED. A better solution that eliminates most of the wasted power is described here: https://electronicsarea.com/light-emitting-diode-connected-to-120-240-vac/ where a capacitor is used used as the primary current limiting device.

Do NOT use an LED on 120 volts this way. It works as you say on lower AC voltages but an LED is only able to withstand 20 volts or so in reverse before breaking down. Add a diode in series with the resistor that is rated for the voltage to prevent the breakdown. (A 1N4001 is a good choice. Give me an address and I'll be happy to mail one to you.)

OK, not seeing any pictures but I understand the original hardware involved now. Your original dimmer is electronic and, as is not at all unusual, has a very small amount of leakage current in the "Off" position. Electronic multimeters place an extremely light load on the circuit being measured and so the tiny leakage is still enough to read 12 volts. If connected to a real load (like an incandescent bulb) the voltage will drop to (very nearly) zero so it works as expected when in use. That will explain the confusing readings you are getting. Get me some more information on the new lights/dimmers and let's see where that leads.

Oops! That's what happens when I responded before being fully awake.

Conventional dimmer switches supply power to two circuits. One circuit supplies the high beam bulbs, the other circuit the low beam bulbs. The two sets of bulbs are not usually active at the same time. The common terminal of the dimmer switch comes from power, one of the remaining terminals powers the high beams the other powers the low beams. There is no ground terminal. I do not know how LED systems work but it sounds like both positive and negative are switched. I would use the original dimmer switch to operate relays to switch the LED circuits.

See post from Onthego above. I looked at it and immediately ordered one from Amazon; I think it'll do nicely! 🙂

@Onthego Thanks for the suggestion and the link! I've been thinking about a DC clamp on for a while and I like the looks of this one!

I'd like to point out one SERIOUS problem with the measurements you have taken. The meter used is for AC only, and will not give accurate readings of DC current.

That is more drop than I would expect, especially since you switched to LED. Get a long jumper wire and ground your meter back to the chassis and start going down the line to see where the drop is occurring. In general, anything over a 10% drop (except in starting circuits) is excessive. While you're checking, also check the voltage on the ground wire of the circuit because a high resistance in the ground will reduce voltage at the load as well.

What chassis do you have? The heater/defroster equipment is generally supplied by the chassis manufacturer and not by Monaco. In general vehicle heater fans work as below. Without the diagram for your particular rig I can't say this is 100% accurate, but; The resistor block is used to SLOW the motor only. For all but the highest speed the motor power goes through the selector switch to terminals on the resistor block, and from the resistor block to the motor. The highest speed is usually not fed from the selector switch because of the amount of current required. Instead, selecting the highest fan speed energizes a relay that feeds power directly to the motor. This direct fan circuit will normally have a dedicated fuse or circuit breaker. If only the highest speed is not working, look for a blown fuse or bad relay. If the highest speed works but any of the slower speeds do not work suspect a bad resistor block or a bad selector switch. If the fan doesn't work at all suspect a bad selector switch or a (lower value) fuse in the selector switch circuit.

Awesome! So glad you were able to find and fix it.

A real quick walk through of what is supposed to happen: 0. We're sitting here with a tank with LP in it, and 12 volts making it from the battery through the fuse to the furnace and the thermostat happily showing numbers that say it's healthy and ready to server. 1. Thermostat decides it's colder than what you told it you like and sends control signal asking for heat. The thermostat does this by sending 12 volts to the furnace to signal it to wake up and do its job. This signal voltage goes directly to the furnace blower relay to run the blower and also goes to the sail switch. 2. After a delay of 15 seconds or so the blower relay clicks on and sends main power to the blower motor. If your meter shows the thermostat signal is making it to the blower relay and the relay clicks (listen carefully, the click isn't loud and doesn't happen for a while!) measure to see that the relay is really sending power to the motor. No power, bad relay or relay not grounded. Yes power, bad motor. 3. The blower motor starts moving air and within three or four seconds the moving air turns the sail switch on. The control signal goes on through the sail switch and on to the high temperature cut-out switch. 4. If the high temperature cut-out switch is OK and the firebox isn't VERY VERY hot, the control signal goes on through to the control board.You should be able to measure the control signal at the high temperature switch, both in and out. 5. On getting the control signal, the control board wakes up and twiddles it's thumbs for another 30 seconds or so to make sure any explosive gas is flushed out of the system and then passes the control signal on to to the gas valve and to the spark igniter section of the control board. If this is working you will hear a fairly loud "Click!" from the gas valve and a "tick, tick, tick..." from the electric spark igniter. 6. The gas valve clicks open and allows gas to go to the burner, where the spark lights it, making the familiar "Whump" of the gas lighting, followed by the rumble of the burner. If the gas doesn't light, then there wasn't any gas to light or the gas valve didn't really open or something is keeping the spark from lighting it. Here's where the control board earns its pay by shutting the gas valve off and going into a fairly complicated sequence of purging, and trying to relight the burner. If you got this far it's a good time to evaluate your abilities and maybe call a pro to take over because it can get pretty hairy to fix from here on out. Take your trusty meter and try to follow along with the above narrative and see if you can find where the expected sequence stops and you'll probably find the bad actor! If not, report back here with how far you got and what you found and maybe we can help! Good luck!

I will be watching with interest! I'm particularly interested in what you plan to use for a power converter/charger. I haven't done any extensive research, but all that I have looked at are designed to operate at a higher voltage than is advisable with LiFePO4 batteries. The three-stage charge regime used by lead acid batteries does not fit with the lithium chemistry. Lithium batteries are usually charged with constant current followed by constant voltage.

The thermistor type has two terminals, one of which is ground. That can be accomplished either with a second wire OR by screwing it into a metal tank that is grounded depending on the sensor. All that I have seen were grounded through the body and only had a single wire, but that was years ago. No idea what the modern ones look like. A single wire thermistor sensor will show around 100 ohms if measured between the body and the connector. A current probe will show infinite resistance between body and connector. The current probe usually sticks into the coolant an inch or more, while the thermistor is only about 1/4 inch.

There are two types of coolant level sensor that I'm aware of. The one on my 2000 Endeavor works, as you suspect, by detecting the tiny current passing through the coolant to ground. The other type uses a thermistor that is heated by current. That passes current to heat the sensor and detects the different amount of cooling of the uncovered sensor vs the cooling of the coolant. The "grounding" type will show low coolant if the sensor is disconnected and the thermistor type will show "normal" if disconnected. The thermistor type has to have a good ground to work, and gets hot enough to burn you if the business end is touched!

When minevfroze several years ago it showed the same symptoms. I finally traced the problem to the pressure switch in the pump. Unfortunately a replacement switch wasn't available so I had to replace the entire pump. If you can get to the wires going to the pump check to see if you have 12 volts. If you do the problem is the pump motor or the pressure switch. If no 12 volts then keep looking for devices already mentioned by others above.

My 2000 Endeavor has a circuit that energizes the boost relay whenever EITHER system gets above a set voltage. That way, either charging system keeps both house and chassis batteries charged. If both systems drop below a high state of charge it drops out, preventing a load on one system from killing both sets of batteries.

The only time I would consider it "normal" for it to cycle that way would be on initial startup of a cold room or a large change in thermostat setting. In that case, the thermostat will sometimes "short cycle" faster than the blower relay delay. After the room coming up to temperature you should never see short cycling happen.

To quote Burt Gummer of Tremors fame "I feel I was denied critical need-to-know information"! You should have mentioned this in your original post as it is symptomatic of another problem with these furnaces. The flame detection system uses (depending on model) either the igniter electrode or a separate electrode placed in the flame to detect when a flame is present. If anything causes the flame to go out, or to be pushed away from the electrode, the control board will detect this and drop back to the "purge, ignite" stage. As noted by astgerma above, a burnt out burner can cause a "no light" situation as well as the flame detection intermittently failing during operation. I would pull the burner and give it a good look. While you have it out also get a flashlight and check in the burner housing for mud dauber nests or other obstruction.

I had this situation and it was caused by low battery and a sticking gas valve. If the furnace will operate normally with the generator running then the gas valve would be the likely cause. As others have stated, the blower WILL run continuously if it fails to light and this is by design. The complete sequence (from memory) is: Thermostat powers the blower relay and sail switch. On detecting air flow, the sail switch applies power to control board Control board delays for "purge timeout" (around 15 seconds?) Control board powers up spark igniter and gas valve. Control board monitors for flame; if no flame for a time interval, the control board goes back to purge timeout. If no flame detected after 3 tries of "purge, ignite, retry", control board shuts down and does nothing more. BLOWER KEEPS RUNNING! If flame is detected, igniter is left "off" and furnace heats until the thermostat shuts it down. If control board detects loss of flame, it will go back to "purge, ignite, retry" point. Once thermostat is satisfied, blower relay and control board are turned "off". The blower relay is a thermal type, and will continue to run the blower for 30 seconds or so, then stop. As I said, this is from memory, and it is also possible that different control board versions will vary the sequence somewhat. I can only state that the three I have tested work this way.

Drum brakes are famous for being grabby if the shoes get contaminated with something that attracts moisture. With high humidity the shoe will become sticky and cause it to grab or chatter with light brake application. They will quickly dry out when used and work normally until allowed to rest and again absorb moisture. You can sometimes cure the problem by applying the brakes while driving and burning off the contamination, or by removing the drum and cleaning the shoes and drum.

Really? Then please explain why on my 2000 Endeavour the fuse is ONLY protecting the short cable going to the inverter while the cable going all the way to the front distribution panel and the generator has NONE? The 30 amp breaker on the inverter is on the AC side at 120 volts, which is coincidentally the same wattage as 300 amps at 12 volts.

Former vehicle electrical system designer here. The fuse is most likely there to protect the inverter from catching fire if one or more transistors fail in a shorted condition. That is a fairly common failure mode, and the circuitry around the transistors will not stand up to the current if it happens.

Just a wild thought: could it be your tank heaters? I'm sure it isn't cold enough for them to be on if working properly, but if the thermostat is hosed.... That's the only load I can think of that's pretty much invisible.

I don't know about your coach, but my 2000 Holiday Rambles Endeavor has a large relay that cross connects the chassis and house batteries . The relay control board cross connects the systems if either battery bank reaches full charge. This system is easy to recognize by the presence of a switch on the dash that will also energize the relay, allowing the use of the house batteries to help start the engine. If you have this system you can easily disable the cross connect by disconnecting the small wire between the relay and the control board. Adding a switch in the wire would allow you to turn it off at will.