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I’ve got this 1990 Lincoln Towncar, and it’s getting chilly here in NEPA. I notice that when the heat control is on “Defrost/Heater” the heat is fine, but on a really cold day if I try to put it on “Vent” the air that comes out is maybe lukewarm. The floor setting produces no air at all, which is most likely a blend door issue but I don’t think its connected to the poor heat problem. Would this be a Heater Control Valve? Or does anyone know something particular with this car and poor heat? I’m assuming that the good heat I’m getting on Defrost/Heater is coming from the AC. Let me know if there is anything I need to know particular about this car, or what else you would diagnose as a potential problem. Thanks!
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Most low heat problems are due to air in the cooling system, and the bubbles of air have a little party in your heater core. Try bleeding the cooling system first.
Eric’s video:
http://www.youtube.com/watch?feature=en … UpXgAJ1gjU
Good luck, and keep us posted.
Quoted From Beefy:
Most low heat problems are due to air in the cooling system, and the bubbles of air have a little party in your heater core. Try bleeding the cooling system first.
Eric’s video:
http://www.youtube.com/watch?feature=en … UpXgAJ1gjU
Good luck, and keep us posted.
+1
That is a great video and just for reference, you dont need to locate and use a bleeder valve when bleeding cooling systems.
I’ve watched Eric’s video before and here is my question (and perhaps Eric could answer this himself since he made the video?). My Towncar doesn’t have a cooling fan that kicks on when it’s needed, it’s a continuous fan driven by the drivebelts. So in this process, how do I know when to release the RPM’s and return the car to idle after the rest of the process? Any help on that would be appreciated – thanks!
You’re basically waiting for the thermostat to open and flush the block. Once the top radiator hose is a good bit hotter than the bottom one, you will know that you are bleeding the whole system.
I think it’s important to note that you said the heat was fine in defrost just not when you put it in vent or floor, with that information I would say that you probably don’t have a problem with air in the cooling system or the heater core. You can verify this by getting the engine hot and putting the heat on, then go to the heater hoses at the firewall and feel them, if they are both hot then the heater core has flow through it and that’s not the problem, if one is hot and the other cold or luke warm THEN look to the cooling system or a restriction in the heater core.
If memory serves that HVAC is a vacuum system meaning that it uses engine vacuum to activate the different doors inside the HVAC that direct air to different parts of the passenger cabin, if this system should fail defrost is the default setting setting BTW. This is where things get complicated however because if you find that the problem is actually with the mode doors inside the HVAC it could be a number of things causing this from the selector on the dash to the vacuum servos on the different mode doors and the vacuum lines connecting them. First find out if you have flow through the heater core and we’ll take it from there.
Eric, would any kind of vacuum leak cause a problem with HVAC? I know at this time I do have a leak coming out of what I believe is the MAP sensor but cannot be sure. There might be others also, but I know there is definitely one there. Thanks for your help, I will do as you suggested with the further diagnosis.
Oh and more thing to make clear, I’m getting zero anything out of the floor setting (when its only on the floor mode). No air at all is coming through the floor when only on floor mode, however when it turn it to the defrost/floor mode, then I do get heat out of the floor vents.
I have no clue how i missed the issue with the vents, sorry.
The best way of testing for vacuum leaks if with a smoke machine and yes your HVAC system is all vacuum operated.
Finding a vacuum diagram for your vehicle would be handy here. You could possible check out our ‘How To’ section as there is a free web access to Chilton’s online. I’m also trying to find you a Youtube Video also that will help.
http://www.youtube.com/user/realfixesre … ayGTFR9gHs
Found it. Its for A/C but same principle.
First verify that you have flow through the heater core and then worry about the HVAC. No a vacuum leak elsewhere should not effect the HVAC.
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