Checked coolant, checked tubes to heater vary hot in and out, checked out side air intake and cab air flapper ( works with A/c) checked a/c and cab temp on dash with fan running engine running turned to a/c cold got cold turned to hot got a little warm, lot of air movement knob turned to defrost, some when moved to floor position did replaced thermostat 50/50 mix the one valve that has wires to it I could see movement when I moved the heat/a/c knob, this would also move the outside and cab air flapper I pulled the glove box out to get access to some of the heater assy
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Re: 1999 dodge 5,9 diesel warm heat only
First thing I would do is flush the heater core with a 4 to 1 mixture of water and muratic acid. Put it in there and blow it out both ways 3 or 4 times. Let the acid mix set for about 10 minutes before blowing it out with air. This is a cheap fix, if it works. $7 and your time. Got to say though, it only works about 30% of the time. The other 70% is to remove the heater core. Dodges/Chrysler su(k. To get to the heater core, you have to drop the steering column, and remove the entire dash. Then remove the heater/A/C plenum to remove the heater core. Buy a manual to do this. Way to many hidden screws and bolts. This job costs about $800 at a garage. It takes about 8 hours to do, if you know what your doing.
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In order for this question to be answered, there are various questions to be answered. What kind of problem? Blower not blowing the heat out? Blowing air but it's not heated? It could be a number of reasons for this question, actually need more specific diagnostics of the problem, otherwise the list could be anything from.....Check the hoses going into the firewall, if they're not warm/hot check to see if the correct amount of coolant is in the radiator/reservoir system, bad thermostat, blower motor, blower motor fuse/relay bad, bad air diverter (moves the flapper inside the air box from cold air to warm air or outside air to recirculating air) heater core plugged, leaking heater core (again there would be insufficient coolant in the system).
CHECK all the vent hoses, are they connected, no ob strucctions, when the last time you replaced the cabin air filter ? do you have one? look @ your owners manual, also, you may need to have several heater controls, or other control on as well, see owners manual, anything fall into the defroster vents ? replace thermostat @ engine. see how this works for you, good luck
Locate the heater hoses and feel for temperature.Should be warm to the touch. There may be an external heater control valve next to the firewall that is either vacuum or cable controlled. the lever on the side opens and closes: warm coolant going into the heater core,inside the cab. If the valve is stuck,no heat. If the vacuum to the valve is ZERO,it should open. If the heater control vacuum hose is leaking air,you should get hot air ALL of the time. people in the winter want heat NOW. Bypass the heater valve,under the hood with a section of copper or plastic tubing. Even if the heater core is partly plugged up,you will still get some heat. If the control valve is stuck closed: NO HEAT. Listen under the dashboard for a hissing sound.That may be the problem for the control valve not opening.(Turn the fan off) I'll assume this is a late model truck.
when car is at operating temp both heater pipes should be more or less the same temperature. If one is cold, try getting the car up in the air so the radiator or expansion tank is higher than the heater...release (carefully) the pressure cap and give the engine three good revs, see if any air comes out and heater pipes equalise. I there is no air in your system you may have a heater water valve fault. Try to locate valve and see what contols it (mechanical , electrical, vacuum)..maybe itcan be manually moved to open, maybe it neds to be replaced.
If you replace it, the air must be bled from the cooling system (see above), but run car until warm with cap off and air will bubble out.
always check coolant levels later when car is cold. Top up coolant as required.
I'll assume for now that the blower motor is working.
Now, there are a couple of things things to check.
1. Easiest thing to check is the coolant level. If the coolant is low, your heater will not give any warm air. Hopefully this is the problem as it's the easiest fix.
2. The thermostat. When the engine and coolant are hot, your top rad hose should be hot as well. See if the rad hose is hot to the touch. If it isn't, your thermostat might be faulty. It's a fairly easy and cheap fix as well.
Make sure the raditor is full. Don't just check the overflow tank but pull the cap when the engine is cold and make sure the fluid is to the top. If that is good then check vacuum line that controls the flapper that diverts air from airconditioner to heat. My 1999 Dodge 1500 had this problem and it was a cracked vacuum line.