Mastertemp humming

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Rdwaggie

Member
Jul 6, 2020
9
Texas
Moved from HERE

Hi folks -
I am having the same issues with a MasterTemp 400 blower not coming on and a service heater light on.

The AFS light is on but goes away when I blow into the air flow pressure switch tube so I think the board is functioning properly. I can also hear the click on the board for the relays kicking on power. The fan spins freely by hand.

With the multimeter attached to the power going to the motor I get ~13.8v on red / black before the heater relay turns on and 240v after the relay turns on.

below are my test results:

BK to Y = no read on multimeter
R to BL = no read on multimeter

C1 to BK = 26.8 ohms
C1 to Y = no read on multimeter
C1 to W = 27.0 ohms

C2 to BK = no read on multimeter
C2 to Y = 0.1 ohms
C2 to W = no read on multimeter

C1 to C2 = no read on multimeter

Continuity:
G to any (BK, Y, W, R, BL, W) = none

Cap = 8.3uF

Does this indicate the motor is bad? And if so, can I have the motor rewound / fixed or buy just the motor and not the full $650 blower assembly?
 
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The blower has 3 sets of windings. 2 main run windings and an auxiliary start winding.

Red and blue go to one set of windings. Black and yellow go to the other set.

For 120 volts, the windings are in parallel. For 240 volts, the windings are in series.

The auxiliary start winding is in parallel with the black --> yellow winding.

Remove the capacitor and test for resistance from red to blue and black to yellow. The values should be the same.

Label the capacitor wires C1 and C2. Test from C1 to C2, C1 to black, C1 to yellow and C1 to white.

Test from C2 to black, C2 to yellow and C2 to white.

To test the motor directly wire as follows:

For 240 volts, Black to hot leg, Red to the other hot leg, blue and yellow connected together.

For 120 volts, red and yellow to one line, black to the other line and blue and white connected together.

Note: I think that this is right, but I can't guarantee it.

It's presented as is.

If you want to test like this, you do it at your own risk.

Do the resistance test first as that should tell us something.

1659974223940.png
 
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C1 to black and C1 to white go through the start winding and those numbers should be the same or close.
C1 to yellow goes through the start winding and the black/yellow winding and this should be the start plus the black/yellow winding.

What does "no read on multimeter" mean?

Is it O.L?

C1 to BK = 26.8 ohms
C1 to Y = no read on multimeter
C1 to W = 27.0 ohms

1659976103864.png

BK to Y = no read on multimeter
R to BL = no read on multimeter

If these are O.L (Out of limit or Open Line), then the windings are probably open.

It would be unusual for both to open at the same time.

Retest to verify.

C2 to BK = no read on multimeter
C2 to Y = 0.1 ohms
C2 to W = no read on multimeter

C2 to black is the black/yellow winding.
C2 to yellow should be 0 ohms or low, so that's OK.
C2 to white goes through the start winding and the black/yellow winding and this should be the start winding plus the black/yellow winding.

C1 to C2 = no read on multimeter

C1 to C2 goes through the start winding and the black/yellow winding and this should be the start winding plus the black/yellow winding.

It looks like only the auxiliary start winding is good.

How old is the heater?

Maybe try the direct power test, but at your own risk.

The heater wiring might be different from different years and different model, so the above might not be correct.
 
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I tried to post this in one of the existing threads but it told me it was closed and I had to start a new one.

I have a MasterTemp 400. The blower does not turn on and the AFS light is on although it goes off when I blow into the air flow switch tube so I think the board is doing what it is supposed to. The blower motor spins freely by hand.

Here are the test results:

BK to Y = no reading on the multimeter (Fluke brand)
R to BL = no reading on the multimeter

C1 to BK = 26.8 ohms
C1 to Y = no reading on the multimeter
C1 to W = 27.0 ohms

C2 to BK = no reading on the multimeter
C2 to Y = 0.1 ohms
C2 to W = no reading on the multimeter

C1 to C2 = no reading on the multimeter

Continuity:
G to any (BK, Y, W, R, BL, W) = none

Cap = 8.3uF

Does this indicate a bad motor? If so, can I have the windings re-wound / repaired? If not, is there a way to buy just the motor and not have to buy the full blower assembly?

Many Thanks!
 
Rdwaggie said:
I tried to post this in one of the existing threads but it told me it was closed and I had to start a new one.

I have a MasterTemp 400. The blower does not turn on and the AFS light is on although it goes off when I blow into the air flow switch tube so I think the board is doing what it is supposed to. The blower motor spins freely by hand.

Here are the test results:

BK to Y = no reading on the multimeter (Fluke brand)
R to BL = no reading on the multimeter

C1 to BK = 26.8 ohms
C1 to Y = no reading on the multimeter
C1 to W = 27.0 ohms

C2 to BK = no reading on the multimeter
C2 to Y = 0.1 ohms
C2 to W = no reading on the multimeter

C1 to C2 = no reading on the multimeter

Continuity:
G to any (BK, Y, W, R, BL, W) = none

Cap = 8.3uF

Does this indicate a bad motor? If so, can I have the windings re-wound / repaired? If not, is there a way to buy just the motor and not have to buy the full blower assembly?

Many Thanks!
Click to expand...
Blower is only available as an assembly. I've seen ones have their motors repaired at an electric motor shop. I wouldn't do it/have it done for them as this blower has air and gas going through it unlike most other LoNox heaters that only meter the air. Haven't heard of any problems, but I won't accept the liability and I'm not sure my insurance would cover it either if there was an issue. Just my take.
 
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1poolman1 said:
Blower is only available as an assembly. I've seen ones have their motors repaired at an electric motor shop. I wouldn't do it/have it done for them as this blower has air and gas going through it unlike most other LoNox heaters that only meter the air. Haven't heard of any problems, but I won't accept the liability and I'm not sure my insurance would cover it either if there was an issue. Just my take.
Click to expand...
Ah - got it. So replace the whole thing if determined to be bad.
 
JamesW said:
C1 to black and C1 to white go through the start winding and those numbers should be the same or close.
C1 to yellow goes through the start winding and the black/yellow winding and this should be the start plus the black/yellow winding.

What does "no read on multimeter" mean?

Is it O.L?

C1 to BK = 26.8 ohms
C1 to Y = no read on multimeter
C1 to W = 27.0 ohms

View attachment 444446

BK to Y = no read on multimeter
R to BL = no read on multimeter

If these are O.L (Out of limit or Open Line), then the windings are probably open.

It would be unusual for both to open at the same time.

Retest to verify.

C2 to BK = no read on multimeter
C2 to Y = 0.1 ohms
C2 to W = no read on multimeter

C2 to black is the black/yellow winding.
C2 to yellow should be 0 ohms or low, so that's OK.
C2 to white goes through the start winding and the black/yellow winding and this should be the start winding plus the black/yellow winding.

C1 to C2 = no read on multimeter

C1 to C2 goes through the start winding and the black/yellow winding and this should be the start winding plus the black/yellow winding.

It looks like only the auxiliary start winding is good.

How old is the heater?

Maybe try the direct power test, but at your own risk.

The heater wiring might be different from different years and different model, so the above might not be correct.
Click to expand...
Correct - it shows OL

it did seem odd - I have tested 3 times with the exact same results all times.

I think while I was repairing the manifold and the motor assembly was set off to the side (long story - had to re-tap some of the screw holes on the heat exchanger) that it rained and got the motor wet - if that is at all a helpful clue. It worked well before that.

The heater is 8 years old but has run perfectly well until a freeze took out the plastic manifold.

I am pretty handy and happy to try the direct power test at my own risk but not entirely sure the steps on that. Is it just jumpering the red / blue and blk / yellow together? What would doing this tell me? Just remove potential errors in testing?

If the motor is determined to be bad, and the unit is 8 years old, would you spend $650 to replace the motor or replace the entire unit for $4k+? My inclination is to repair but a circuit board plus something else going wrong sort of gets me to a new unit - but would rather not have to go that route if avoidable
 

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Cap is rated at 8uF +/- 5%. It tests at 7.52uF
Red to Black: OL
Red to Yellow: OL
Blue to Black: OL
Blue to Yellow: OL

what should these read? I retested everything and got the same readings as above
 

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Combustion chamber is dry. The motor did get wet from rain when I had the top pulled off while I was working on replacing the manifold. I didn't think that would ruin windings after it dried out though.

So we are thinking the motor is toast?
 

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