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M998 heater duct/tube replacement

Thumper580

Active member
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Location
Virginia
Trying to replace the heater duct hose that goes over to the drivers leg area. The one behind the doghouse is good.
Thinking it's torn or damaged. Very little air flow to the drivers side. Passengers side is good. Searched the TM's but did not see anything about replacement of the drivers side duct/hose or how to access it.

Suggestions? Thanks.
 

Action

Well-known member
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Location
East Tennessee
Different hoses for different models.
With the pdf of the parts book open, do a search for "diverter". That will take you straight to the defrost hose page.
If you have an older model, the driver floor air passes behind the duct just above the doghouse. There is no hose in there. If you open the driver side dash vent, it will reduce the amount of pressure to the driver feet. The hose behind dash attaches just to the left of the dash vent.
If you have a newer model with a plastic vent by the driver right knee, then the driver heat hose runs directly across the top of the engine.
 

Thumper580

Active member
269
209
43
Location
Virginia
Different hoses for different models.
With the pdf of the parts book open, do a search for "diverter". That will take you straight to the defrost hose page.
If you have an older model, the driver floor air passes behind the duct just above the doghouse. There is no hose in there. If you open the driver side dash vent, it will reduce the amount of pressure to the driver feet. The hose behind dash attaches just to the left of the dash vent.
If you have a newer model with a plastic vent by the driver right knee, then the driver heat hose runs directly across the top of the engine.
Its a 1986 M998.....
 

mgFray

Well-known member
Steel Soldiers Supporter
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907
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Location
Southern Minnesota
I just replaced the missing heater ducting on the drivers side, but I want to make sure I have everything routed properly.

Does anyone have any pictures of where the duct drops down (aiming toward the floor), and how it's attached (or is it more less just lose)?

The 24P-2 Figure 331 shows a hose clamp on the downward end, but I don't see where it would be attached to.

Also the routing, I have mine routed above the cluster, then it snakes down over the steering wheel, through the hole if the left side and down toward the floor. I suspect that may not be right, but I didn't find any other pictures and it seemed to make sense when I did it. (Also doesn't appear to have anything rubbing on the hose.)

Any pictures would be appreciated, thanks!
 

mgFray

Well-known member
Steel Soldiers Supporter
656
907
93
Location
Southern Minnesota
IMG_4919.jpeg
IMG_4920.jpeg
IMG_4918.jpeg
this is the routing I ended up with, but I’m not sure it’s correct. (My HMMWV was complete missing the duct, so I didn’t have anything to go off of)
 
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