Monitor 41 issue

[cadman44]

I have a Monitor 41 that I "inherited" when I bought my house around 6 years ago. It has worked great up until now. When I turn on the heater, it goes through the start-up routine and then shuts off and all of the bars blink. I have spent most of the weekend going through most if not all of the posts here and have learned quite a lot. The combustion post does get hot and the fan works normally. I believe that I am not getting any fuel to the pot. I have an external lifter pump that works fine. I have plenty of fuel in the sump tank. I have taken it out and cleaned it as described in other posts. I have taken out the line between the solenoid pump and the pot and it appears to be clear. I can blow air through it. I believe that it has something to do with the solenoid pump. I have contacted my local distributor and was told that the solenoid pump is discontinued.

If it is the solenoid pump, any suggestions as to where to find one?

Is it possible that it is not the solenoid pump? If so, any suggestions as to what I should test next?

Thanks in advance for any help.

[cadman44]

**UPDATE**

I was able to find a solenoid pump. The part is pretty expensive though (and non-refundable). The service guy that I can get the part from mentioned that the solenoid pump rarely goes bad but it does. Is there a way to test the solenoid pump to make sure that it is the part that has gone bad? I don't mind spending the money on the part if it is going fix my problem but I would hate to end up wasting the money if it is something else.

He also said that it could be the air pressure switch or a split in the small rubber hose that connects to it. I can easily check the rubber hose. Is there a good test for the air pressure switch?

As a side note, I am very impressed that this service guy is taking the time to help me versus just selling me a part that I may not need. I will definitely get any parts I need from him even if I could save a few pennies by going elsewhere.

[HayZee518]

with proper air flow through the pressure or air proving switch, the switch closes making up a part of the pre ignition string. you can merely jump out the switch to see if that makes a difference. the solenoid pump gets its pulsating voltage from the taisan controller on the motherboard. it really has to be totally gunked up before it won't function. don't take it apart or you'll regret it putting it back together. another thing, don't mess with the adjustment screw on the fuel float. it doesn't take much to knock it out of whack for float level.

[cadman44]

Thanks for replying so quickly Hayzee. There is a wealth of information on this site and most of it seems to come from you. You definitely know your stuff and are quite helpful.

After reviewing the site more last night, I saw a post that you had about testing the air pressure switch. I took the spade connectors off the back of the air pressure switch and jumpered them. I turned the unit on and it started right away. I was thrilled. Does that test conclusively prove that the switch is bad or could there be an airflow problem as well. The fan appears to be working correctly. The flame did have a lot of orange. I did put it back together quickly just to see if it would fire. I know that I have to replace some of the gaskets that fell apart when I disassembled some parts. I didn't want to invest in new gaskets if I couldn't get the unit running.

I found the McMaster Carr number for the gaskets that you posted. I also need to replace the burner mat. I know you mentioned that there was a comparable part in McMaster Carr for it but I couldn't find it. Can you post that number? I know that the original mat is "D" shaped. Do I need to match that shape exactly or just cover the bottom of the pot? If I need to match it, is there a place that I can find the dimensions?

Again, thanks for all the help. Without this forum I may have given up on the unit.

[HayZee518]

for test, disconnect the air input to the combustion blower. use the air out port of a small shop-vac and feed air into the blower hose. now start your heater. once a flame is lit look into the view port and see what the flame looks like. if it is still orange, the holes around the inside of the pot may be clogged with soot. if the flames are blue then it is safe to assume the bearings are shot on the blower motor. the bearings on the blower motor are the same ones used on inline skates. mpi sells bearings but I'm not gonna pay 25 bucks each! inline skate bearings go for about 3 bucks a piece. the burner mat is a coated ceramic fiber from mc master-carr. I'll go look for the stock number. the D shape isn't critical but I wouldn't cover the entire bottom, don't need to. check the tubing that comes from the blower and goes to the air proving switch. if the hose is cracked replace it with a poly hose, you don't need rubber.

[cadman44]

Ok, so it's been a few days since I've been able to work on the heater. I put the new air pressure switch in and put the unit back together. I tried to start it and no luck. It is still the same problem as before. The heater will go through the normal startup cycle. The fan will turn on, the display goes to four bars, the ignitor will heat up, and then it will shut down with all 8 bars flashing.

I disconnected the switch again and jumpered the connectors to see what would happen. It started up right away again. Is it a normally open switch that closes when activated? I have one lead on the NO and the other on the COMMON. I believe that is correct. There are two ports for the air tube. Does it matter which one I connect the tube to?

During the startup phase, I can feel that the blower at the back of the unit is sucking in air. If I move my hand across it, I hear the air pressure switch click open and close.

I'm not sure what to check next. Any suggestions?

[HayZee518]

put your meter on the RX1 range and connect it between the C and NO, now blow into either port. the port that closes the switch is the one to use, the other is open to atmosphere. the air switch is a neoprene disk with a pin in the center connected to a microswitch. constant air flow deflects the diaphragm and pin, closing the switch. as long as there is air flow, the switch stays closed. the air is necessary for combustion. if there were no air the kero fumes would back feed into the blower and your could have an explosion inside the tubing and pot. so the switch is necessary as a part of the safety string. remove the far end of the cappillary and stick it into a jar. start the heater and see if any fuel comes squirting out. if it does then the pump solenoid is ok. if not, then either the controller or the pump is toast.

[cadman44]

I probably won't get a chance to check this until Monday. I will check it then and then repost.

[hawkins111]

air safety switch

The air safety switch is a NO switch. The two outside prongs are used. The hose goes on the top hole.

Sorry for the confusion on my part. The switch does close during operation. The marking on the switch are NO, NC and C in that order. The wires go to the two outside prongs, NO and C.

Again sorry if I confused you.


Tom

[HayZee518]

hawkins, so with air on the diaphragm the switch is open? that don't make sense!

[adnadeau]

Air pressure switch

I measured the pressure in the pressure switch tube with a homemade U-tube manometer. The switch closed around 0.5" of H20

[HayZee518]

So it DID close! Hawkins was saying that the switch is wired common to normally closed, which tells me it OPENS when energized. That's wrong. It's supposed to close completing that part of the initiate string.

[cadman44]

Ok, so I had the chance to look at it again last night. I did check the switch first. It works just as Hawkins said - normally open and top port for the hose. The switch is fine.

I did take the hose out and checked it closely for any holes/tears. I blocked one end with my finger and tried blowing air through it and there are no leaks at all.

I did take the fuel line from the pot and fed it into a cup. It does have fuel going to the pot.

I turned the unit on. It went through the startup cycle. The burner did turn on. I could see a flame (some orange) and it got warm. I will check for plugged holes tonight. I needed to let it cool down last night and it got too late. At this time, the displays shows 4 bars of the 8. After 5-6 minutes from when I turned it on it shuts down and goes to all 8 bars blinking.

The blower (lower left - looking at the unit from the back) turns on right away and I can feel it sucking air in. If I remember correctly, the fan (middle/right - looking at it from the back) didn't turn on at all. If the fan is bad, would that cause the unit to overheat and shut down?

[HayZee518]

this seems like a raw way of troubleshooting but trial and error seems the way to go. after a while you'll get to know what's supposed to happen and when. for the main fan - it gets its signal from a plenum switch - I think its the top one which is normally open and closes when the plenum temperature warms up. for now jumper it out. it'll start as soon as the unit starts, so don't be alarmed. see if the heater goes to full heat and keeps on running. as long as it heats and runs - you could ascertain that the fan might be bad. e-14 would give you a lockout for overheat and shut down. remember to unplug the unit to reset the computer. merely shutting it off won't reset the computer.

[cadman44]

Thanks again for all the help. I don't mind putting the time in and trying different things. I will check that when I get home from work tonight.