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My coach has had weak heat coming front the engine coolantpowered heater at the dash. The dash coolant temp gage has consistently read around 183 or so degrees. I've been through the whole system and everything seem to be properly hooked up and operating as designed. So what gives? 

Using an IR temp gun, it seems my coach has 160 degree thermostats rather than the usual 180 degree ones. So, I've ordered the 180 ones. I have installed a new temp sensor for the dash gauge that seems to have dropped the indicated temp into the range of the IR indication. 

I was originally concerned that changing thermostats would make any engine overheating issues worse, it won't because once the thermostat is wide open cooling is only limited by the effectiveness of the radiator and fans and willhave nothing to do with the thermostat temp setting. Also, all the information I found states that the engine is expected to run better at the higher temp. So hopefully I get a two-fer; more dash heat and a better running engine. That's just plain hot.
Have you checked the booster pump in the engine compartment?
The booster pump is almost new, the solenoid was removed. Water temp at engine thermostats 162 or so, water temp exiting heater core 156, a drop of 4 over entry temp.
Have you confirmed that the booster pump is turning when the temperature control is set to max heat temperature and the heater is turned on? Are you getting decent air flow through the heating system. Mine bedeviled me until @"encantotom" discovered that all three blower motors were wired backwards and therefore totally ineffective.
My pump has valves on both sides, might check to see if both completely open.
are you sure the simple water heater hose valve is opening at the front when you move the heat lever on the dash control?

tom
Jon, if I read that right you measured water temp going into and out of the heater core at the front of the coach.

162 in and 156 out, correct?

If so, the heater core is either plugged with grime on the fins, or gunked up inside. If I read the post right you are getting hot water to the core, just no heat exchange at the core.
Richard: I think my memory is faulty regarding the core inlet and outlet temps. Based on comparible core sizes my heater core should be rated at 35,000 btu/hr. The big question is how they calculate that. As a Chem E, you know the variables. I did a rough calculation that suggested that with whatever the water temp drop was, at reasonable pump flow rates according to the manufacturer's chart the core was in good shape and that boosting the water temp by 20 degrees would probably get me to the rated heat capacity. Yeah, I know, I'm a recovering engineer and think way too much.

I am getting a 40 degree rise in air temp, but since I don't know the air flow rate I can’t use that to confirm the 35,000 on the output side.

Based on the above commentary, all the coolant flow circuit is operating just fine. A year or so ago I checked the fan and they are operating ok.

It’s not that I'm without heat, it's that, as Forest experienced, a bit weak.

I do need to research the standard method manufacturers of heater cores use to rate their heater. I will share what I discover. And I will do a before and after report. Y'all be good now hear.
Jon, do you run with a VMSpc? I haven't paid much attention to the dash gauges since I set up my VMSpc 8+ years ago. The readings are digital and much more accurate than the dash gauges.
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