JD4720 Cab No air (heat) r coming from left side cab ports

[orlo]

Hi:

I was just out in my 4720 to clear some snow for the first time this winter. Probably
the first time I've used the heat. A/C worked fine in the summer, etc.

Odd issue - There are 6 rotatable and open/closable ports on the roof for heat & A/C.
All the ones on the right were blowing hard, nothing coming out of the ones on the left.
All 3 on the left seemed dead. It has been outside (I usually store it indoors) so I suppose
something could have froze but it seems odd. Even if I close all 3 louvers on the right, i can
hear the fan working but nothing comes out on the left.

I looked at a bad diagram but I couldn't find an explanation for this. The louvers are not
clogged. I don't think there are 2 fans up there but who knows.

Any have any ideas?

Thanks,

John O

 

[beenthere]

Mouse nest or two... my first guess.

Time to take it apart.

 

[gimmodog]

something has the ductwork clogged. only 1 fan in the 4720. Take the bolts out on top of the roof then lift roof off to get inside.

 

[jd110]

Don't want to confuse you but there are 2 blower motors. There are 2 separate fuses that feed them an separate relays.Not sure what serial number range you have, but on above 610,000, fuses are F3 and F4. should be 20 amp fuses. I would check those first. If they are good, then you need to check relays and blower motors under the roof.

 

[gimmodog]

Don't want to confuse you but there are 2 blower motors. There are 2 separate fuses that feed them an separate relays.Not sure what serial number range you have, but on above 610,000, fuses are F3 and F4. should be 20 amp fuses. I would check those first. If they are good, then you need to check relays and blower motors under the roof.

Offhand I'm not sure of the serial number of mine but it has 1 fuse for the heater/AC blower and the radio is also on that fuse. I'm sure of this because I just had to replace the fuse this summer. Mine is a 2007 model so later models could be different.

 

[orlo]

Don't want to confuse you but there are 2 blower motors. There are 2 separate fuses that feed them an separate relays.Not sure what serial number range you have, but on above 610,000, fuses are F3 and F4. should be 20 amp fuses. I would check those first. If they are good, then you need to check relays and blower motors under the roof.

I'll check this tomorrow. It's a 2010.

I took a borescope and looked in through the holes. Clean as a whistle, no ductwork, the whole roof is pressurized but
it does appear to be split into right/left halves so two blowers would make sense.

 

[kennyd]

Taking the roof off is pretty easy with two people, manageable with one if necessary in case it's more than a fuse. There are indeed two fans.

 

[oosik]

My EXACT thought - beenthere. Sold one of my ATV's this summer. Had not been run in over three months. Hit starter - it just grunts. Take side cover off - big mouse nest binding everything up. Somewhat embarrassing - otherwise, great relief. Pull out mouse nest - blow out fines with air nozzle - ATV starts up like a champ.

ORLO - when you take it apart to clean out the duct - do not skimp on blowing it out. Least wise - you fire it up and get instantly pelted by little black "pellets". Advice - keep your mouth shut the first couple times you turn it on. I know - they have an "unusual" taste. I had a big 'ol mouse nest and etc in the heater ductwork on my pickup.

 

[orlo]

Don't want to confuse you but there are 2 blower motors. There are 2 separate fuses that feed them an separate relays.Not sure what serial number range you have, but on above 610,000, fuses are F3 and F4. should be 20 amp fuses. I would check those first. If they are good, then you need to check relays and blower motors under the roof.

I checked, and that was it - F4 was blown (F3 is a combo and right motor, F4 is labeled for the left). Blew it almost right away but at least now
I have an idea. Later I'll bring it in my shop and let it thaw out then look at it. If I'm lucky maybe it was just some moisture that froze up
(It's been about 0 overnight lately and 10-15 during the day). I never would have guessed there were two blower motors. Thanks.

I will check for mouse invasion but I see no signs of it - I have Sleds, ATV's, campers, and have seen signs and evidence of mouse invasion
before before, and unless the mice are really clean, it's not mice.
Also, when I was looking in the roof with the borescope last night it was squeaky clean, not even dust on the inside on the camera.

I'll thaw it out and figure it out the rest and let you guys know what the remainder of the problem was.

Thanks for all the help.

 

[beenthere]

If a short is blowing the fuse, replace the fuse with a 12 v bulb on socket so wires can be inserted in fuse slot.

A short will cause the bulb to light, and then you can more easily move wires around and search for the short. When the bulb goes out, no more short.