No dash heat

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adun015

adun015

Well-known member
Joined
Oct 22, 2008
Posts
283
I am not able to get my dash heat / defrost working. I had a engine heating problem when we first purchased ( used ) but found that to be a dirty radiator and low coolant. A/C was low on charge as well. Now the A/C will run you out but still no dash heat/defrost. I am sure that I have located the heater core in front of the passenger side. There is a grate and you can see the core so I am pretty sure I am not experiencing any leaks. I have also located the lines going in and out. I have what I am pretty sure is the vacuum line but there seems to have been some type of repair to it. It has a section with shrink tubing on it. I can hear what seems to be the doors opening and closing when I change over from A/C to heat but it doesn't seem to be changing a lot on the heat side from defrost to mix to floor only.
I keep reading something about a valve that could be closed from the engine to the heater core but I can't find anything in the manuals regarding location.
Any advise on what to do next would be appreciated as I am at a loss now as the next step. I am going to see if I can check for a clog in the heater core by fixing up a hose and flushing with the garden hose but I don't feel any heat change on the hoses to and from the core which makes me think there might be a valve somewhere that is closed.
The engine is a diesel 330 CAT.

Thanks much.
 
If the heater core is clogged there will be little or no heat in the hoses going to the heater core, so they will feel cool.  Flushing the core will probably pinpoint what the problem is.  Sometimes it's not possibly to clear the heater core enough to product good heat.  There's a good possibility you'll need a new heater core. 
 
Or there could be a problem with the system that operates the various doors in the heater itself not permiting air to be directed over the heater core to the various outlets. On modern vehicles this is accomplished with vacuum in very small 'pipes' that are well know to break or become disconnected. In a deisel powered vehicle a tiny vacuum pump is needed for this purpose although many gasoline vehicles also have them. There is likely a valve in the line  to admit hot water to the heater core that could be defective as well.
 
The valves you are referring to are by the engine in line with the heater hoses. I have two of them, one in the supply line to the heater and another in the return line. I usually shut them off in the summer to maximize my A/C output. I have get underneath the engine to operate them.
There is another valve up front  that stops/reduces the supply of hot water to the core used for temperature adjustment. It is usually the first thing your hose connects to prior to the water line going to the heater core.
 
I have traced the water lines but don't seem to be able to locate any valves, ball nor gate, anywhere. I can see the top of the engine when I pull the cover under the bed but no valve. I have crawled under the engine and can't trace the lines past the rear wheels. They go up in the frame and I can't see where the run from there. Is the any drawings or pictures that I can refer to?
I did another radiator clean today and was under the engine and on top and looked everywhere but no luck.
Regarding vacuum I can hear the doors open and close when I go from A/C to heat, but still can't confirm if there is a vacuum leak anywhere. I can see one valve (green line ) on what I believe to be the heater core inlet. It is opening and closing as we move the position back and forth. There seems to be another vacuum line (blue line) that runs into the dash and that one has a repair it.
I did not get a chance to fix up a back flow to check the heater core but will give that a try next week-end.

Thanks for all the replies it is very helpful.

Any idea if it turns out to be a bad heater core on best place to get one and appx. cost?
 
I have found the valves, thanks Harry B., They were both off. Have turned on let engine reach operation temp and still no dash heat/defrost. Did not get any warm up on either of the hoses so I'm still stumped as to problem. I will try a heater core flush and keep trying to see what the problem is.
 
That's odd. Now I am thinking there is a reason that they were turned off.
I assume that you have not always owned the coach and that someone else shut the valves.
Valve handles inline with the hoses is the open position on mine. Make sure there are no leaks anywhere.
The heater cores have been known to leak on the early 2000 models if I remember correctly from reading some older posts.
 
The cost of a heater core will vary depending on the size and type but they're usually not very expensive. The labor to replace them is usually more costly than the part itself. Heater cores can leak and instead of fixing them, people will sometimes take a shortcut and bypass them altogether. That won't hurt anything but you won't get any dash heat. If you can see the hoses, look at how they're routed to see if the heater core has been bypassed.

Kev
 
Both valves were off and are now on. I let the engine warm but no dash heat. I am thinking that 1) may not have allowed sufficent engine temp to open the thermostat. I assume ( but could be wrong ) that there would not really be any water circulation until that happened. 2) do a flush on the heater core itself. I can see where the lines run in to the heater core and do not see any leak there. I can also see a dash grate which I assume pulls air from the cab into the heater core and do not see any leaks there either but again not sure if the engine was warm enough to open the t-stat and get the water moving. As Harry B. pointed out some may turn the valves off to maximize the A/C. I did have a very weak A/C charge and maybe that was why they were turned off.  I did notice a petcock just in front of the rear-most valve. Is that to drain the coolant for a change out?
 
Just a thought but if that heater core is clogged or in need of cleaning inside you might want to check it before running that engine and pushing the gunk in the heater into the engine. No need to contaminate a radiator you already had cleaned. When you had the radiator cleaned was it just cleaned on the outside or was it flushed out.
 
catblaster said:
Just a thought but if that heater core is clogged or in need of cleaning inside you might want to check it before running that engine and pushing the gunk in the heater into the engine. No need to contaminate a radiator you already had cleaned. When you had the radiator cleaned was it just cleaned on the outside or was it flushed out.
Click to expand...

Just cleaned on the outside of both radiators. No flush. I think the recommendation of a heater core flush might be the best way to proceed. At the very least it will give me the peace of mind that all possibilities have been looked at.

Thanks again for all the help regarding this. New to the Diesel world and getting a crash course in lots of stuff.

 
You might also consider replacing the thermostat.  What does your coolant temperature look like, idling and under load?
 
jstrubberg said:
You might also consider replacing the thermostat.  What does your coolant temperature look like, idling and under load?
Click to expand...

Before the clean it was normal to high even causing an occasional alarm.
Now it is showing ion the guage between 1/4 and 1/2 depending on the load.
I haven't had it out since I did the last cleaning. I was able to get a lot of gunk again
this time around and I added a little coolant as the tank was showing at the low side when
cold.
I have thought about changing the t-stat as well.
 
If the heater core flush does not solve the problem there is another possibility.  Though not often seen, the water pump impeller can rot, resulting in lower coolant circulation.  Sometimes the circulation will be enough to prevent overheating, but not sufficient to push the coolant to the heater core. 
 
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