blend door arm works bud no heat

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mk8fanatic

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My 97 mark has been intermittently losing heat. Looking at the blend door actuator I have observed the arm that comes down to the gray lever and everything works well. Even way up there I can clearly see the black arm on the motor moving and seems to be ok. Can the shaft that goes into the heater break internally and leave the levers and arms working correctly? I would really hate to take out the whole dash to find that this was not the problem! Sometimes the heat works though, but I cant think of anything else it can be.
 
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Ok....I am now really confused! I got a new blend door motor and took the whole car apart only to find that it is not broken. Also when I hook up either of the motors and change the climate control functions It does nothing....This has got me worried because it was at least moving before I took the car apart..and now I have no idea why the heat comes and goes...Please help
 
I'm not sure of the Gen2 EATC diagnostic procedure, but have you checked that?

Also, is it actually heat/no heat or is it an intermittent blower? If you turn the fan knob up to high, does the blower work?

Maybe you have air in the coolant system?

Just throwing ideas out there. :eek:
 
It seems like it an all or nothing thing with the heat, and the blower motor works
great. I even swapped out the climate control unit to be sure it was not that. My bigest problem is that now that the whole thing is taken apart I cant get the old or the new blend door motor to do anything when plugged in. Your Idea of air in the coolant is a good one.....If I can get this blend door to work again I will put it all back together and look at that idea.
 
I should also tell you that on my other 97 mark I can hear a distinct thump noise when I change it to heat when the car in question does not, but when it is working and I turn the car off or take it back to A/C it will. Do you know of any other doors or flaps other than these two that the blend door motor works and the one above the blower motor. It really doesn't seem to be any one of those.
 
I just did the test on the climate control unit and I got the codes 025 135 and 155. After I did the test the blend door now works again and has been installed with the modifications done to prevent breaking down the road from now.
 
It directs air to all vents correctly. No heat but the blend door works perfectly, I swaped the climate control to be sure, and it was good. Also the heater core is free flowing and works well. I really need a diagram to show me what else there is in the heater unit...The blend door motor is electric and there are of course vacuum parts right..I know the door above the blower motor for recirculating works off vacuum , where are the others and what do they operate?
 
This is for a Gen1 but I think is the same for all the vacuum motors on the gen2.

Vacumn2.jpg


I'm wondering if the cold engine lockout switch is maybe malfunctioning?

Again... from a Gen1 manual...

Temperature Control Lockout Valve and Switch

The temperature control lockout valve and switch (18D371) is located in the water bypass tube (8555) assembly, is the engine temperature input shown in the system block diagram and operates in the following manner:

~ Its function is to prevent A/C blower motor operation when heating is required and the engine coolant temperature is below 49°C (120°F).

~ When coolant temperature exceeds 49°C (120°F), the temperature control lockout valve and switch opens and turns the A/C blower motor ON when heating is required.

~ The temperature control lockout valve and switch will not prevent A/C blower motor operation when cooling or defrost is required.
Click to expand...
 
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Temperature Control Lockout Valve and Switch? I wonder if Gen 2 mark have that....or where it would be. I have looked all around the heater hoses and don't see anything...just straight off the motor and into the heater core and then back. Also I have found and observed all vacuum lines and where they go, and all vacuum actuators are working properly with full range of motion. So It doesn't seem to be that. If I could only find that lockout valve :confused:
 
Oh....after clearing the EATC I found that the only code that remains is 135, and I cant find what that code means anywhere.
 
I am stuck with the hole dash pulled back and all I think could be wrong is something inside the plenum.....maybe the receiving part where the blend door motor goes into, or whatever flap it moves. I dunno but the dealer said that the 97/98 models do not have the Temperature Control Lockout Valve and Switch. I do know that the vacuum actuators work and so does the blend door motor, I have flushed out the heater core and found it to be in perfect working order. Also the air that comes out seems to be colder that the outside temp.....kind of like the a/c is working some, but at the same time I can feel the heater get warm where the core is located...
 
I have the same code and am trying to find out what it means aswell.

Right now i dont beleive the blend door moves but i do have codes 135 and 155....idk, this is annoying.

Thanks god i have 2 cars....
 
Ok guys.....my nightmare has come true....I decided to make a fake square actuator stub out of aluminum and stick it into the heater plenum just to see if the flap in there was working. It was real loose and then nothing was there for it to go into at all :eek: So I guess now I get the fun job of taking the dash the rest of the way out and then try to get that whole heater unit out as well. Hopefully I can fix it and I will with out a doubt replace the heater core while I am in there. About the only thing that has me a little worried is those A/C lines that will have to come apart....anyone have any advice?
 
mk8fanatic said:
About the only thing that has me a little worried is those A/C lines that will have to come apart....anyone have any advice?
Click to expand...

Sorry to hear of your situation. :frown:

You will need special fitting disconnect tools for Ford AC systems. But first, to maintain the integrity of the AC system, I would take it and have it evacuated prior to disconnecting the lines. After your work, then take it and have the AC system vacuum pumped/tested and then re-charged with the proper amounts of refridgerant and lubricant.
 
I live in north TX...but it still gets cold on those 4:30 am trips to work in the winter.....also I like my cars to have all functions working if you know what I mean. :D ........I have almost got the dash out and cant seem to figure out how that main harness that comes through the firewall comes out. It is the very large one that is white and in the far upper left corner.
 
Sorry, I just thought if you were near me, my son *might* be able to help. TX is a bit of a drive though. ;)
 
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