M998 Heater quit working

[sagreen83]

Was using my heater today up until lunch. Was working great. Then came back from lunch and the heater blower no longer works on either Low or High. Anyone had this happen out of the blue? Blower didn't seem to be making any odd noises or anything.

Thanks!
Scott...

 

[JoeJrTheBarber]

The stock heaters in these trucks blow, I would say with your issue check fuses and work your way more into it.
This is exactly why I am in proccess of running a secondary heater on the back wall of my M998.

 

[doghead]

What did you have for lunch?

 

[sagreen83]

The stock heaters in these trucks blow, I would say with your issue check fuses and work your way more into it.
This is exactly why I am in proccess of running a secondary heater on the back wall of my M998.

That heater looks like its gonna work!

It doesn't seem like my heater blower is bad. I went out the next day, started the beast, and the heater worked. Turned it off and it quit again. Seems like it works the first time you start it each day, but quits after that.

Scott...

 

[porkysplace]

What did you have for lunch?

Probably cold cuts , no heat.
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Probably need to head to the trouble shooting section of the TM's section 2-21

TM-9-2320-280-20-1.pdf
TM-9-2320-280-20-1 TECHNICAL MANUAL UNIT MAINTENANCE for M998 series. Part 1. Jan 1990

TM's for the M998 series

 

[wheelspinner]

Check your voltmeter. Mine shows no charge when the heater fan won’t work. I flip the start box on and off until I hear the heater fan come on. I’m sure I have a relay sticking, but whatever feeds the fan seems to also feed the exciter on the charge circuit.

 

[sagreen83]

Check your voltmeter. Mine shows no charge when the heater fan won’t work. I flip the start box on and off until I hear the heater fan come on. I’m sure I have a relay sticking, but whatever feeds the fan seems to also feed the exciter on the charge circuit.

Thats an interesting idea! How do you flip the start box on and off? Just turn the key on and off?


Scott...

 

[wheelspinner]

Thats an interesting idea! How do you flip the start box on and off? Just turn the key on and off?


Scott...

The start/run switch, like you are waiting on the glow plugs

 

[sagreen83]

Finally got a chance to get a voltmeter on things. I had 24 volts on the fan wires so I was getting power. Just to check, I banged on the heater blower cover. Motor jumped to life

I ordered a new motor from ebay. Cheap fix.

Scott...