Jim McGarvie

Our Knight has an ISB 5.9 260 hp. It has an electric lift pump mounted on the passenger side, low rear of the engine. I have no way of telling whether it continues to run when the engine is running. But I do know that when I use it to prime the fuel system after changing the fuel filters it only runs for less than 30 seconds. Typically I have to repeat that cycle several times before the engine will start.

Follow up from the OP: 1. I replaced the floor outlet below the thermostat with a metal one, and bent the louvers to all point away from the thermostat. No change in performance. 2. I replaced the control board with a Dinosaur. No change. 3. I replaced the LP regulator. No change. 4. I bought a manometer and checked the LP pressure with the new regulator. Ours is 12" with furnace and water heater operating. Should be plenty; our local RV shop owner says that is not too high. 5. Ordered a "tune-up kit" from PDX RV, which includes Burner Assembly, Electrode, Electrode Gasket, Limit Switch 190°, and Sail Switch. 6. In preparation for replacing the above parts, I removed the furnace from the coach. 7. After removing the furnace I discovered the installation was only using 3, 4" duct openings. According to the service manual for our model, it requires a minimum of 4, 4" ducts. I believe inadequate ducting may be the reason for our short cycling. 8. I plan to add a fourth 4" duct. The only feasible way of doing that is to simply route it to the side of the cabinet containing the furnace, below the sink, and to an outlet behind the couch. I will give another update when the project is complete. In the meantime, any and all comments are welcome. Jim

Thanks for that info. I have a "tune-up kit" coming which includes the limit switch as well as a burner assembly, ignitor/flame sensor and sail switch.

Wow! Thanks for the information, Harvey. What would cause the burner to "blow out?" You mean by wind? This occurs all the time, not just when it is windy. I wish we could remember whether this has always been the case. If so, maybe we have inadequate ducting. If not, perhaps something is blocking a duct or ducts. It would be great if I could get it to operate as you describe.

This discussion raises the question, what is normal cycling? We have an Atwood 8535-IV-DCLP furnace, 19 years old. Our burner is normally on for 60% of the time the blower is running. Should it be greater than that? I was concerned we were wasting battery power (we most often dry camp) with the blower running but no burner, until I checked the air temperature at one of our ducts. When the burner is running it is approx. 160 degrees, but when the burner shuts off and the blower keeps running it only drops to about 140, so I guess we aren't losing too much. If 60% burner-on time is about normal I won't worry about blockages; if it isn't I will start looking. We have another issue which may or may not be related. Intermittently (yeah, I know) the furnace will shut down prior to reaching the thermostat setting temperature. It will run normally for three or so burner on/off cycles, then after an off cycle the burner comes on with a "wumph" sound like it is trying to light but doesn't stay lit. After the cool-down cycle the blower shuts down. I can repeat the cycle by turning the thermostat off and waiting a couple of minutes, then turning it back on. If I don't manually recycle it, the furnace will reset itself after an hour or so and try again. I am guessing this issue might be caused by the flame sensor. Any thoughts would be very welcome!

Yep, that was my experience.

I was going to get the Talin tank, but check the measurements closely. It was larger than my stock tank and would not have fit. And I don't think plastic tanks are still available. Those are the reasons I went with the Source Engineering.

I recently replaced my original plastic tank after trying to repair it twice. The repairs did not last. I bought the aluminum one from Source Engineering. It wasn't exactly plug and play, but close to it. Not a difficult job.

Accumulator maybe?

Happy anniversary, Scotty, to you and the others who helped. This site is a great resource, populated by wonderful, helpful RVers.

I'm thinking the access to the back of the shower faucet is probably a removable panel in the rear wall of the pantry. Wouldn't that be about the right height?

Good info, Harvey. Thanks. I probably won't be able to check those measurements without emptying the tank, which I won't get around to for a while. Hopefully I'll hear back from the supplier and will learn what type I have and how to check it.

Thanks for the info, Jim. I don't have the part number; the sensor was included with a new tank. I haven't yet had a response from the source. My schematic shows a low coolant module but it is notated "ISC only". We have an ISB, so I assume no module.

Thanks, but this is a new sensor. It may be defective, or maybe I have a break in the wire between it and the dash.

Good info, Harvey. Thanks. Would the thermistor type need two wires? Ours only has the one. Thanks Bob.

Our low coolant light remains on regardless of coolant level. Is there some way of testing the sensor and/or the rest of the circuit? It is a one-wire sensor mounted low on the side. I cut a couple inches off the end of the wire and crimped on a new terminal, but no joy. The connection on the sensor for the wire is clean. It might help me to understand how the sensor works. Does it detect a ground through the coolant? Thanks.

Thanks Rick. I didn't think about turning on the headlights; I'll give that a try the next time. I agree with you about not bypassing the relay. BTW, I looked today and I don't appear to have a solid state battery isolator, just a plain, old-fashioned, White-Rodgers relay. There are two trigger wires going to it, and I assume it is used to parallel the battery banks both for charging from the alternator and for the battery boost function.

Thanks for the input, Gary. It is sounding increasingly like this is normal given the way our coach is wired, so I will do the same as you and turn off the solar system while driving. Yes I did, to correspond to our new AGM batteries. Would that make a difference in the appearance of the alternator fail light? Maybe because the charge voltage is higher for AGMs? Thanks, Bob. I guess I'll just try to remember to turn the solar system off when driving.

Thanks for that info, Harvey. Interesting how many different configurations there are.

Not sure what you are suggesting there.

I don't remember seeing anything like that, but I will look tomorrow.

Interesting. I was thinking it was a simple relay connecting the two battery banks when the engine is running, but it sounds like I was wrong. I will check it out.

Hi Rick. I did connect the solar system to the house batteries. But when the engine is running aren't the house batteries connected to the engine batteries so that the alternator can charge the house batteries?

This morning right after start the alternator fail light came on and stayed on except for a few brief periods. I checked the dash voltmeter and it was reading 14V, higher than its usual 13.5V. When I came to a stop a few miles later I turned off our new solar system, thinking maybe there was some kind of conflict. Sure enough, on the way home the alternator fail light never illuminated and the voltmeter was reading as usual.We recently installed the solar system so I’m not accustomed to it yet. Is this behavior normal? Should I turn the solar system off when driving?Thanks.

Thanks for that reminder, Bob. I discovered that a few years ago and bent the fins of the register away from the thermostat. I think it may have helped. But we had our flooring replaced this summer and they replaced our register with a plastic one whose fins can't be bent. I will replace the register and try that again. Jim Thanks, I'll do that too.