ws721 Posted January 25, 2014 Share Posted January 25, 2014 Ok, I may not be the sharpest tool in the shed BUT. How do you remove the heater motor from an MH? Do they come out together as one unit? If so how do unhook the duct work? Quote Remember if it's got a hood it's no good! Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/ Share on other sites More sharing options...
BAD DOG Posted January 25, 2014 Share Posted January 25, 2014 They're under the passenger seat tale the seat and top off the heater box and you'll see them should be 2 side by side I don't remember having to remove any duct work. I put a heater in the compartment under the bunk on the MH I had because I found the factory heat ok for the passenger and the defrost with 2 fans up in the windshield, but the floor of the drivers side was cold an extra heater behind the seat made it toasty. But your factory heater motors are under the passenger seat. Hope this helps. Quote Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-228598 Share on other sites More sharing options...
BAD DOG Posted January 25, 2014 Share Posted January 25, 2014 They're under the passenger seat tale the seat and top off the heater box and you'll see them should be 2 side by side I don't remember having to remove any duct work. I put a heater in the compartment under the bunk on the MH I had because I found the factory heat ok for the passenger and the defrost with 2 fans up in the windshield, but the floor of the drivers side was cold an extra heater behind the seat made it toasty. But your factory heater motors are under the passenger seat. Hope this helps. Quote Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-228599 Share on other sites More sharing options...
BAD DOG Posted January 25, 2014 Share Posted January 25, 2014 If I remember right they are mounted on a frame in front of the heater core and A coil for the AC. You'll need to unbolt that frame from the heater box and remove the 2 motors as an assembly. You should be able to match them up aftermarket if Mack doesn't have them. Quote Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-228600 Share on other sites More sharing options...
ws721 Posted January 25, 2014 Author Share Posted January 25, 2014 I have the seat and cover off. I was wondering about the frame with the two motors in it. You answered my other question, my feet will be cold when driving it. Quote Remember if it's got a hood it's no good! Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-228608 Share on other sites More sharing options...
BAD DOG Posted January 25, 2014 Share Posted January 25, 2014 Been a few years since I worked on one of those heaters, I don't remember it being too bad to work on worst part will be getting the old squirrel cage off the motors they should be steel most of the time you end up replacing them to because they are always seized on. Quote Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-228616 Share on other sites More sharing options...
farmer52 Posted January 25, 2014 Share Posted January 25, 2014 As stated above, they are located under the passenger seat. According to the parts book, the blower housing needs to be removed and then the squirrel cages. The motors attach to a frame. Motor part number is 4379 RD556261 (need 2).There is a third motor located in the RH storage compartment under the sleeper. The motor PN is 4379 RD553100. Quote Ken PRR Country and Charter member of the "Mack Pack" Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-228628 Share on other sites More sharing options...
MHfred Posted January 25, 2014 Share Posted January 25, 2014 I have the seat and cover off my 1989 and there are 2 screws along side the panel next to the dog house. Those screws are at the top and I did not see anything holding the bottom into place. Boths fans are attached to that side panel. Let us know how you make out getting them out.EDIT: Are you sure the motor is bad? I don't think both fans operate at the same time all the time. Quote Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-228630 Share on other sites More sharing options...
ws721 Posted January 26, 2014 Author Share Posted January 26, 2014 The front fan never works and the wiring to it is melted. Im gonna try again here in a min. It's cold out there and the wind is hollowing. Quote Remember if it's got a hood it's no good! Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-228761 Share on other sites More sharing options...
ws721 Posted January 26, 2014 Author Share Posted January 26, 2014 I did get the frame with the heater motors out. FYI. There are 2 screws down low in the front of box that hold duct work together. Now all I need to do is get the squirrel cage off the motor shaft. Allready have the set screw out and sprayed shaft with PB blaster. Keep you updated if you like Quote Remember if it's got a hood it's no good! Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-228819 Share on other sites More sharing options...
farmer52 Posted January 26, 2014 Share Posted January 26, 2014 Suggestion - take pics to document the changeout. TIA Quote Ken PRR Country and Charter member of the "Mack Pack" Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-228823 Share on other sites More sharing options...
ws721 Posted January 26, 2014 Author Share Posted January 26, 2014 LOL. I would gladly take pics. But I am severely electroincly challeneged. I admire those of you who post pics of cool things. The Ex set up our website. That's why that doesn't get updated as often as it should. I have a big computer, scanner, digital camera. Now if I can figure out how to make them talk to each other. Quote Remember if it's got a hood it's no good! Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-228825 Share on other sites More sharing options...
ws721 Posted January 31, 2014 Author Share Posted January 31, 2014 Got the heater motor in. PHEW!!! International had the motor and resistors. No one had the squirrel cage. So, a little heat and prying we saved the old one. Went to northern N.H wed at minus 10. Had frost on the inside of cab, froze my feet!! Just ordered an MH book on heater/ac. Hopefully that will shed some light on the subject. Not quite ready for the Ice Roads yet Quote Remember if it's got a hood it's no good! Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-229623 Share on other sites More sharing options...
MHfred Posted February 1, 2014 Share Posted February 1, 2014 I found out that my fresh air vent door was stuck closed on my MH. I thought that was odd since it fails open and the truck had sat for about 10 years. Maybe you should check yours since the outside air would force air through the heater core. The fresh air vent door is in the portion of the heater box closest to the passenger door and it is hinged on the side next to the doghouse. If you turn on your key and have air built up you should hear the dampers change postions as you cycle through the different vent control positions and you can see the fresh air door if you are looking down into the heater core area. Here is a diagram out of my "Climate Control System" book for you until yours arrives.EDIT:The diagram is on it's side but click on the view tab after it opens and you can rotate it clockwise to read it.MHvent.pdf Quote Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-229779 Share on other sites More sharing options...
ws721 Posted February 1, 2014 Author Share Posted February 1, 2014 If I can get the volume of air that's coming out of the defroster to the floor vent I think it would be ok. I didn't want to run the Cruiseliner in the salt but that truck has good heat where you need it Quote Remember if it's got a hood it's no good! Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-229828 Share on other sites More sharing options...
BAD DOG Posted February 2, 2014 Share Posted February 2, 2014 Yeah the fresh air vent is in a stupid spot on them getting fresh air off the right front steer tire. So when you drive in dusty places it blows all the dust in the cab. Make sure that door is able to open and close it will make a difference. And yes parts for the heaters in an MH are not the easiest to come by so a guy wants to grab up any bone yard parts out of those MH cabs you think you might need someday. Quote Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-229962 Share on other sites More sharing options...
ws721 Posted February 2, 2014 Author Share Posted February 2, 2014 Good to know. Thanks for the info. Quote Remember if it's got a hood it's no good! Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-230177 Share on other sites More sharing options...
MHfred Posted February 10, 2014 Share Posted February 10, 2014 Any update yet? I know it is still cold as hell and working outside is difficult. Thanks. Quote Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-231672 Share on other sites More sharing options...
39 Baby Mack Posted February 10, 2014 Share Posted February 10, 2014 There's another problem with the "MH" heater system that I encountered years ago which is losing air getting into the cab.The ductwork going into the cab runs on the outside under the floor above the R.H. steering tire.The air actually leaves the inside of the cab from the heater/A.C. box and travels in a duct under the floor and re-enters the cab at the very front of the cab on the R.H. side.There it bolts up to another duct above the floor with the floor sandwiched in between.The duct on the bottom is double wall blow molded plastic with threaded inserts in the hollow parts on the top, that's why you won't see the nuts under the floor.There is a gasket between the floor and this duct along with a gasket that seals the inside duct to the floor.If these are deteriorated along with the gasket where the snout on the blower motor assembly enters the duct going under the floor you can lose an awful lot of your heat and or A/C out to the outside.I don't know whether I'm bragging or crying, but through the years we operated them I became quite intimate with them!RonR Quote Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-231675 Share on other sites More sharing options...
ws721 Posted February 10, 2014 Author Share Posted February 10, 2014 That's good to know. I did replace both resistors and blower motors. Now im trying to get air to the drivers side floor. I will check the duct work again. Bought a book on MH heater/A.C. Only problem its for 86 and up. Mine is 85. The book covers the 2 lever air control where as my 85 is a 3 lever cable over electric control. Learning as we go. Quote Remember if it's got a hood it's no good! Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-231680 Share on other sites More sharing options...
39 Baby Mack Posted February 10, 2014 Share Posted February 10, 2014 Yours was made by Signet Systems, later ones were made by Red Dot.Both have their own problems.In one respect you don't have to worry about all the air leaks in the dash control and all the air cylinders.There's only one air cylinder in your truck the one for the fresh air door.Ron Quote Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-231703 Share on other sites More sharing options...
ws721 Posted March 2, 2014 Author Share Posted March 2, 2014 Just an update. All your info was very helpful, along with the Climate Control manual. The door in the heater pleumun that divereted the air from floor to defrost was in the wrong position and the control cable was broke. Im going to rig up something here for a cable that will work that door. As the dash controls don't seem to move the cables enough. Thanks again for of your input Quote Remember if it's got a hood it's no good! Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-235264 Share on other sites More sharing options...
TommyZ Posted March 4, 2014 Share Posted March 4, 2014 That's good to know. I did replace both resistors and blower motors. Now im trying to get air to the drivers side floor. I will check the duct work again. Bought a book on MH heater/A.C. Only problem its for 86 and up. Mine is 85. The book covers the 2 lever air control where as my 85 is a 3 lever cable over electric control. Learning as we go.Suggestion Russell: Go to Home Depot, buy a propane salamander and a 100 lb.'er, lay it (the tank,) in the bunk and the salamander pointed at you on the doghouse, and you'll have all the heat you'd ever need! Quote Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-235637 Share on other sites More sharing options...
BAD DOG Posted March 4, 2014 Share Posted March 4, 2014 A friend of mine bungied a propane tank and salomander in the passenger seat of his 77 international Coe years ago when he had heater trouble and was waiting for parts to get it fixed. He said it roasted him out of there and he had to keep a rag to wipe the windshield because it kept sweating so bad. He figures all the trucks meeting him on the highway probably wondered what the orange glow in the passenger side was at night. Quote Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-235640 Share on other sites More sharing options...
ws721 Posted March 4, 2014 Author Share Posted March 4, 2014 LOL. Nah, I think I get it fixed. Either that or ill buy a winter bomb truck maybe say a truck with a hood. That way I could put a wood stove in it just cut a hole in the roof for a pipe. After all, its just a convential Quote Remember if it's got a hood it's no good! Link to comment https://www.bigmacktrucks.com/topic/34388-mh-heater-motor/#findComment-235661 Share on other sites More sharing options...
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