Heater Problem

I have a 1999 Dodge Ram 1500 Quad Cab 318/5.2L V8 Magnum. It has 116k miles and runs near to perfect. The heater, however, does not. If I leave the truck running for a half hour,
then I get some heat, but not a lot. It doesn't heat up any faster if I am driving. What are the most likely culprits, and in what order should I check them? I would prefer to have the cheapest options first. This is kinda important, as I am in Oklahoma and have a 9 month old. Also, links to any helpful diagrams/photos/guides would be greatly appreciated. I have been looking for the FSM but have not been able to find it for this model. I have only had this truck for six months, and as far as I know, all except the tires is stock. Thank you all for your time.
Corby
P.S. Sorry if this double posts...using an unfamiliar newsreader
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Corby wrote:

Well what does the temp gauge say? Is the engine itself coming up to operating temp (195 or so) If not then I would say it's probably a stuck open thermostat.
If the engine gets up to temp and you still don't have heat check the water control valve under the hood. It's installed in the heater line and has a vacuum line on it. (YOUR truck may not have this, some did some didn't depending on the options installed)
If it is open then check the blend door under the dash and make sure it is moving to send air through the core. If all of that stuff is OK then you might have a plugged heater core.
--
Steve W.

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Lack of water/coolant in the system will cause this as well.

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PlowBoy wrote:

pressure checked. Ask them to do the rad cap as well. If the rad cap won't hold pressure then the temperature will not rise as high as it needs to (works like a pressure cooker). A thermostat that's stuck open or won't close will allow the engine to run cooler. If the engine is reaching its high temperature and the rad cap is working and the thermostat is opening and closing as it is supposed to, then the hot coolant may not be getting to the heater core inside the vehicle and that could be for a number of reasons. There is a mixer valve that can be operated by vacuum that allows the coolant to be diverted from the system into the heater core and if that is working, the core may be plugged. Off the top of my head those are all the things I'd try and I hope I have given some points for you to check out. Richard
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