Finding the heater activation valve.

If it has a heater shut off valve, it's usually on the right side between engine and firewall. Most newer trucks don't have them, only put on aftermarket.
They do not save fuel and not meant to. The only purpose is to boost the air condition coolness in the summer.

Possibly the heater valve in the side box for your bunk.

 

First off, what kind of truck do you have. Most have the heater valve on the right side fo the engine somewhere. Look for 2 hoses that break off from the rest. There should be 2 valves. On my truck its near the alternator. Be careful, they may be to hot to touch. With them closed the A/C works better, but I never heard of getting better MPG. If those valves are open there are a few other steps to find the problem.

First off, what is your watter temp under load and at 900 rpm idle (after an hour or so) If your water temp isnt getting up your heat wont work great. You should be 170+ while driving and at least 130 idle. Again it depends on truck and motor. These are ball parks.

If temps are fine, there is probably a blockage somewhere in the system. You heater core could be corroded and blocking or clogged. You could also have a blower problem. Does it blow a nice strong air flow? Does it make a difference on recirculate or not? Also check the sleeper heat, does it work any better or worse?

 

1 , thermostats may be bad or you are too light to build heat at highway speed.. a winterfront like most canadians use will help make sure u leave some air flow. some people use cardboard in a pinch 2, if you have air leaks through doors you may need to set bunk heat on medium to help out with front heater to keep comfortable . btw this week alberta got nailed with a storm and temps are frigid.. so treat your fuel or fuel up as close as you can to the border you absolutely dont want bio diesel or southern fuel up there

 

Might also be blend door stuck. Try moving selector back and forth,fresh air,recirculate several times.

 

Anybody should be capable of turning on the coolant taps for the bunk/cab heater cores, that said I have met freezing cold drivers that had no idea their truck had cab air filters. If the filters are clogged up with dust you will not get much heat.

Like mentioned you need coolant heat to get heat, and engines should be running a minimum of at least 165 even at idle year round and never idle an engine less than 1000 rpm.

 

Depending on your truck, there may be 2 or 4 valves depending on whether the sleeper lines tee off the cab heater supply or connect directly to the block. One valve of each pair will be near the alternator, and the other towards the rear of the block behind the turbo.

As pointed out, check your cab-air filters, and also if it's a cable actuated heater valve, make sure the cable is moving the valve. Also, if your coolant level is low you won't get proper flow through the heater core.

 

And why not idle the engine at 1000 rpm when your not needing heat?

I idle my at 650 almost all the time. Only when it's below 32 degrees and I'm needing additional heat, I'll bump mine up to around 900.

Are you thinking of the myth that idleing is bad for these engines?

 

Low idle doesn't create enough load/compression to set the rings firmly against the cylinder which creates multiple problems.

Cylinder glazing
Blow by
Cold oil
fuel contaminated oil
slobber
Carbon build up
wet stacking...etc.

I couldn't care less what you do to your engine, I just don't agree with some of what I've read here. I've seen all of the above with my own eyes...ask a mechanic, they see it all the time.

These newer engines with dpf and def systems are even more susceptible to problems caused by idling. Shut it down if possible.

In my opinion oil temp should be a minimum of around 125f and coolant 180f.

 

hey we have no heat in a 2014 kenworth. cant figure it out