No heat

[MaiNiaK]

M1078 No heat (fixed with pictures)

My blower works and my heat lever is pulled out but I'm getting no heat.

At the moment I can't lift my cab to check if there is a gate valve closed, that would prevent coolant from reaching my heater core. (I did however find some great info on here on how to fix my stuck latch)

Does anyone know if there is a gate valve?
or do I have an issue with my pull lever assembly on the heater unit?

(edited title to show up better in search)

 

[Suprman]

First think I would check is my coolant level. Most military trucks have an emergency shutoff for the heater core but I have not looked on mine so I cannot say for sure. Did you have heat before?

 

[MaiNiaK]

No I haven't had heat since I got it.
I just installed one of the zero start block heaters. My coolant level is center of top sight hole.
This is when I discovered my cab latch (lock) is now sticking and won't allow me to tilt the cab.
I was still able to lift the rear right hand side (engine) mud flap, to install the block heater.

Now I need to fix the cab latch so I can check to see if there's a gate valve. Or maybe it's air bound.

I finnaly have some free time to fix the little things that were wrong with mine when I got it. I now have a working passenger side door, and my door seals should be here this week.

 

[Suprman]

Door seals are standard over the counter automotive push on seals. If you drained the coolant for the block heater it could be air bound but probably not if you have been driving and coolant circulating. Maybe you can tap the release pin to open the cab. Is it stuck or no hyd pressure to open?

 

[MaiNiaK]

Passenger side tries to lift, drivers side doesn't, so I'd say the latch is stuck.
I tried gently tapping the button in with a ball peen hammer. It will go in, but as soon as a friend tries to raise cab the button pops back out, even with me trying to hold it in.

yes I ordered the seals on eBay. Just standard 05#

 

[Suprman]

Passenger side is where the cylinder is. Looking at it from the passenger side, pin out is unlocked in is locked.

 

[MaiNiaK]

Then my pin is out. But when I try to lift the cab the passenger side tries to raise and the drivers side seems to go downward. Like the latch is still locked.
The hydrolic pump starts out fine, then you can here it slow down like it's under to much load. Even trying the hand pump it won't lift, the handle eventually gets to hard to pull. At the same spot the hydrolic pump does.

I will have more time at the end of this week. So I'll take it back to my friends garage and see if I can't get the latch apart.

On the passenger door I just fixed, I'm missing the door pull handle, window crank and the plastic cover that goes over the Interior latch handle.

 

[Suprman]

Older Volvo cranks work well and are cheap. Maybe your cab pivot is binding or the catch needs adjustment.

 

[MaiNiaK]

Thanks Suprman.
The door pull, I have never seen one online for sale. But I'm fairly confident I can fab one up fairly easily. (I'll have to dig the forge out)

I will update this weekend when I figure out the heat issue and cab lift.

 

[MaiNiaK]

Back to my heater unit.
The fan switch works, I can shut the fan off and turn it up. I am missing the fan knob but I stole one out of a junk car that's working for now.
The heat pull knob pulls all the way out and pushes all the way in.
The vent pull knob is stuck in the out position.
The defrost pull knob is also stuck but only halfway out.

I have all the TM's saved as pdf files. (Total of 9 of them) Last night I searched the index's of all of them and can't find anything on this heater. I can find info on the M1079 heater that's in the van body, but that doesn't help much. lol

Today I purchased a NOS heater unit from a well known action site. But as of yet have not been able to complete the purchase do to lack of shipping info provided by the seller. The action site won't allow the transaction to be completed. So I have my fingers crossed that this can get sorted out quickly.

 

[MaiNiaK]

My NOS heater unit showed up today.
This unit was a great deal compared to the used ones I've seen going for a lot more $.


They also packed 3 insulation panels in the box. I'm not sure what they go to yet, but I plan to look up the pn.

 

[MaiNiaK]

Door seals and heat make a big difference.

I'll post more pics when I get somewhere with WiFi

 

[MaiNiaK]

The cab latch works now. It was low on hydrolic fluid (I should have checked that first).

To get at the 8 bolts that hold the heater in place you'll need to take the front grill off. You'll find your 2 heater core lines there, and 4 of the 8 bolts that hold the heater in place. The cab will need to be tilted to get at the remaining 4 bolts.



There are 2 holes with grommets that the heater core tubes go through. Remember which ones hot in and cool out.
the heater core tubes are normally marked with arrows. One of my truck side tubes had red paint on one, indicating hot in.
The 2 riveted over holes must be for AC application.

 

[MaiNiaK]

On the inside the CTIS has to be unplugged and taken off (there is a ground wire that goes to the bottom bolt).
The plate that holds the service and trailer brakes also has to come off. But first the handles have to come off. These are held on with push pins. I couldn't get my push pins out and didn't want to break my air valves. So I cut the heads off my (weather cracked) handles, so the retaining nut could be taken off to get the plate off the heater unit. (I ordered new handles that will be here today).
On the passenger side take the floor kick plate off and unhook the duct work from the heater unit, then do the same on the drivers side.

There is also an electrical plug that needs to be unhooked when you get the heater pulled out a bit. There is a yellow retaining clip that keeps the plug from coming apart, mine had an added zip tie. Pull the heater core tubes up through the floor and cautiously work your service and trailer brake valves out through the duct work in the heater unit.

The white wire with black end is the power supply to the heater unit. The 2 red (unused) plugs I believe are for the units that have AC.




I forgot to mention. The CTIS plug pulls through the side of the heater unit easier if you pull the grommet out first.

 

[MaiNiaK]

I still need to replace my service and trailer brake handles, that and paint some other interior parts.


Hope this is helpful to others if they need to pull their heater units.
All in all it wasn't to hard to do.