94 Marquis heater control valve - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

rreitz · 08-31-2011, 18:55

How do I test the heater control valve on my marquis? Blower works but no heat when temp lever moved to far right. If I disconnect the electrical connector to the heater control valve and put a volt meter on the 2 connector pins, what should I see if the electrical switch is working properly? If I am getting current at the right time, how to I check if the valve is working (i.e., should I hear a click or something when it is energized?). Thanks.

**Bert** · 08-31-2011, 20:09

You should hear a motor move when the control is moved from cold to hot or hot to cold. Listen closely with the key on and the engine off. The blend door motor is the normal culprit. Do both heater hoses get hot to the heater core?

rreitz · 09-01-2011, 10:22

Okay thanks. I will check the hose temperatures tonight. What I was also looking for is a way to test the heater control valve. If I remove the connector to the valve (under the hood) and apply 12 volts to one pin and ground the other, will I hear something audible to tell me whether the valve is working or not? Does it matter which pin gets the 12 volts? Thanks once again.

**Bert** · 09-01-2011, 21:11

There's no valve for the heater hoses on a Grand Marquis. If something is in the line to the heater, it was added by someone.

**87_Crown_Vic** · 09-02-2011, 00:29

heater cores are simple setup... on the older ones there wasnt really a valve, but instead a sensor... it was to turn on/off the system for the auto climate control stuff... usually what causes ... on the older Grand Marquis it was a wire that moved the blend door and the door would break where the wire connected... vacuum was used for the areas for where air was supposed to go... just sayin how it is in mine, but yours is newer so its probly different... might wanna see if you can remove glovebox or stuff to see the blend door area to see if anything is moving when you move the temp control

rreitz · 09-02-2011, 10:25

Here's what I'm talking about:

94 1994 Mercury Grand Marquis Heater Valve - Climate Control - Four Seasons, Motorcraft - PartsGeek

It's a valve under the hood and came with the car (i.e., not added by someone else). It's in line with one heater hose, has a factory two pin power connector on one side, and some small vacuum lines on the other side. I just wanted a way to determine whether this device was working correctly or not before I take on the more difficult task of trying to get under the dash. Thanks.

**Bert** · 09-02-2011, 17:50

My wiring diagrams from the Ford factory manual doesn't show any heater valve in the system. Either way, with the engine hot and the heater on, both heater hoses should be hot. One more so than the other. If they are, the problem is inside with the blend door.

**87_Crown_Vic** · 09-02-2011, 19:48

that valve is for the aut climate controls... the wiring for it can be fixed by simply putting in a jumper wire between the plug end... them things are a headache...