379 Heater Deflector Control ??

Appreciate the responses. Both in & out heater core hoses are warm/hot to the bunk & up front. Shut-offs are completely open...all of them front and back...checked and re-checked. Coolant is passing through the core. I know this is where the heat is brought...the fan blowing or drawing the heat from the core at this point. Now, fan works fine on all speeds. Air coming out of the bunk vents is not even the slightest bit warm. I know it doesn't make sense but it is what it is. Ductwork is intact or it wouldn't be sending air through the vents.

I'll call Mr Peter Bilt today & see what parts he wants to sell me. I just figured maybe someone else had experienced this.

Edit: Apparently there is one of these electrical actuators (piano box) in the bunk unit too. If so, that would be the culprit keeping the deflector door closed off from the core. I'll lift the plywood today and do a little hands on.

 

I Googled to find something...anything...about the electrical actuator that controls the deflector door on a Peterbilt heater and A/C unit. I had heard they present problems from time to time but I personally had never experienced a failure of one. I decided I would get to the unit and have a look-see for myself. Through the next few posts I am going to include images that may help someone when they have to figure out why the bunk has no heat blowing through the vents even though heater core coolant is hot and valves are open for circulation. In my case, I had lots of heat up front, air conditioning worked but when heat was called for in the sleeper area this winter...only cold air (not A/C) would blow through the vents despite the position of the bunk heat/temperature control on the sleeper wall panel.

I'll use several posts rather than one long post and I'll use thumbs that should open to a larger pic for a clear view if one is interested in the images for reference.

Access to the bunk heater is obviously underneath the mattress and the plywood base under the mattress.



In my truck (a 2007 Pete 379 flattop 63" sleeper), the worst part about getting to the unit was maneuvering the mattress around. I didn't want to take it all the way out so I stood it up on it's side and propped it up enough to get access to the phillips head screws that held the plywood base in position.

First thing you'll notice is the fresh air filter access cover. 2 phillips head screws and lift it out of the way. Just for filter access, these 2 screws are all you have to remove. Then pull the filter straight up. To gain access to the entire bunk heat-A/C unit, there are several more screws to remove including the 4 phillips head screws that attach the plywood base to the plastic molded panel at the end of your bed that holds the cigarette lighter/12 volt plug...and your loose change. No clips or anything...remove the 4 screws and the plastic piece will be loose. The only thing preventing entire removal of this plastic panel is the 12 volt wires to the backside of the lighter receptacle. To work on the bunk unit, no need to disconnect them. Slide the plywood section out of the way.




Immediately I saw the neglected filter (a washable reuseable unit) on mine. I regularly changed and cleaned the front unit's filter under the bottom right corner of the dash but I had never considered this filter. The filter cleaning alone will no doubt help a lot for air circulation in the bunk. That had to be hard on the system having that filter clogged like that. Wifey was right I guess...I don't know everything after all.



The image below shows the actuator unit that controls the deflector door. It is held in place by 3 screws. Remove these with a 1/4" socket & release the actuator from it's perch atop the unit. Unplug the electrical connector to the actuator unit. This little "piano" looking device sits on a plastic post, of sorts, that is connected or part of the door below inside the unit. As I lifted my actuator up and off the projecting post, apparently there is a "default" position for the door once removed because the door slowly rotated back to an open/closed stopping point evidenced by the rotation of the post protruding through the top of the unit that the actuator slides over.

 

A closer view of the "piano"...my terminology only...of the electrical actuator control.



Part number visible here...



Once screws are removed and it's unplugged, it will lift off it's perch easy enough. Here's an image of the unit removed and turned over to see the backside of it.




Next image is a shot of the unit with the actuator removed. Here you can view the protruding post that it sits over. Turning this "knob" with your fingers will reveal the "weight" of the door and as you let it loose it will slowly return to a default position. I'm not sure if it's closed or open at this point. The fan/cage is positioned after this door so it seems the air is "pulled" through the heater core, then on to the duct work and the vents. If this is the case, the deflector door's "default" position appears to be in an open position which would allow heat to pass through.



Since I figured my actuator or "piano" had malfunctioned, I decided to get into it and see what made it work. There are some clips along the split in the plastic case...4 or 5 clips...and the case will separate easy enough. I carefully lifted the top off and saw this...




and a closer look with the first "white" gear/cog removed from the set...



It may be hard to see at first but if you'll look at the larger "black" gear, there are teeth along one half of it that mesh into the teeth on the underside of the first "white gear". Sorry for the lack of better description on the cogs...but you get the idea.

 

Here's an image of the larger black gear that slides over the deflector door's post. On the backside, you'll see the electrical contacts...2 separate copper prongs that slide along 2 opposing copper strips on the base of the actuator unit. I added a little more di-electric grease at this point...that's what's covering the prong ends.



Here's the contact strips on the base...




And a shot of the first white gear removed...




I didn't have my DVOM with me when I pulled this...all I had was my trusty test light. I would have liked to see how the thermostat control on the bunk wall worked in conjunction with this little piano unit.

But I was able to watch it work a little with just the test light. The test light bulb lit from full left (cold) position:






and extinguished at about this notch as I rotated the knob to a warmer setting...



This, of course, was with the switch on the dash up front in the "ON" position for the bunk heat-A/C.

I didn't have a replacement actuator and the closest Pete Store is over an hour away and it's Christmas Eve anyway...so I "blocked" the door in a mid-position so I can get some bunk heat until I can get by a Pete place. Not looking forward to paying close to 100 smackers for one of these..or so I hear. It may be more than that. After I replace it, I am going to try to find a suitable electric motor to repair one...just for the giggles of it.

So...replacement would be very simple...if I had the replacement piece. I was interested in seeing how it worked and if there was any way to repair this from inside. For now, it seems one could replace that little motor inside the units if he could find them. I didn't remove the motor to see if there were any markings on the backside. There were some numbers inked on the top but it didn't look like identifying part numbers. Maybe searching McMaster-Carr or Grainger...or ??? could come up with something. All the plastic gears were still in good condition...teeth were still good...electrical contacts were good...all soldered points looked good. There was nothing obvious that was wrong with the unit which led me to think maybe the little motor was bad. It would be doing a lot of work to roll the weight of that deflector door back & forth over several hundred thousand miles. And if the operator had a brain and remembered to change that filter back there once in a while, it would be easier on everything.

One more thing before you button everything back up...look down there in that corner beneath the heater unit...over in the corner there...yeah, that's it.



Reach down in there and grab those 2 old DVD's you thought you lost and a couple pieces of old mail along with an old manual for a printer you once had laid on the TV tray above. Apparently this is the catch-all for everything that gets lost in the bunk. But I never did find my sock I lost...


Hey, it's Christmas !! Merry Christmas, TTR'ers. Now, just maybe when another owner has similar problems, he'll Google it up & he'll find The Trucker's Report with some pictures to know what he's up against. I couldn't find anything but a Peterbilt Training Module for the HVAC and it did not show any doors or this little actuator/servo unit.

Safe Journey, Drivers.