I have a 2001Grand Marquis that heating system just quit cooling. It only blows heat no matter the cooling setting. I understand there may be a blend door somewhere that could be stuck or not working but I’m not real sure how to check it and where it is. Does hot water always run to the heater no matter what the temp selection is set to? Any suggestions would be greatly appreciated.

   

Results for your 2001 Mercury Grand Marquis 4.6L SFI Heater Control Valve

2001 does list a heater control valve. Should be in smaller of two heater hoses underhood. Check to see that all is hooked up (wiring and or vacuum line) to it and if warm/hot on both sides for a starter,

T
Tom Greenleaf - MetroWest Boston - USA
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http://www.autoacsystems.com/tomgreenleaf/

Thanks Tom. If there is a Heater Control Valve is on my car, it is well hidden. My two hoses come right of the heat exchanger from under the dash (under hood side) and go straight into the block. At least one really appears to do that. The other goes behind the engine and there could be the valve down and behind the engine. If so, I don’t know how I would get to it – very cramped.
The hoses look the same size and are both hot. So I would think if there is a valve, it is open and allowing the heat into the system when it should be off. Is that a correct statement?
Thanks again,

BertOne

Arggh! I haven't happened to run across this exact problem as I think I understand it from your post. This control valve is involved but I simply don't know if it's stuck open or being told to stay open -- OR if a diverter door that would blend available heat and ambient air is the trouble??

Ya - I know these things get tucked in tight spots and aren't so easy to just get right at sometimes. Guess is that the "home" position for this is "open" flow and I'm guessing which isn't helping you much right now, sorry. Don't worry about the hose size as it's just lots more common to make the input hose smaller than the return hose.

Basically I've only deduced that this control valve is stuck, wiring or a vacuum hose to it isn't correct, or the control head (you don't want to go there!) is the problem. Not very good on my part so far.

Any ideas guys? I hate to suggest just tossing parts as a way to fix this.

If you wish come visit the folks at ACsource - just auto A/C discussions there and heaters are a major part of A/C work as heat if put head to head with A/C wins every time! http://acsource.net/...644d7d8eeeb77edc058a

See if that link get you to the Q&A part of that site if needed.......

T
Tom Greenleaf - MetroWest Boston - USA
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http://www.autoacsystems.com/tomgreenleaf/

Hey

Only thing I have to offer is...
I think there is a blend door /actuator on the top of the distribution case...Instrument Panel (Dash) I think has to come out to access.
I have never done one on this type car nor am I too familiar with the Grand Marquis...
Just remember a buddy saying/doing something like this...

Thats all I got...

Thanks Jim. Haven't been there but I think there's a nylon gear that can strip on the actuator - some might be accessable thru removed glove box??

T
Tom Greenleaf - MetroWest Boston - USA
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http://www.autoacsystems.com/tomgreenleaf/