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No cabin temperature...

1458 Views 17 Replies 4 Participants Last post by  amc49
So after a full hose check, rad flush and new coolant, I can get at best 'warm air' into the passenger cabin - which with -5 already and -40's around the corner is not good.

The engine is producing good heat, everything seems to be flowing as it should but none of that lovely heat is getting into the cabin.

As an aside, last winter we thought the fan speed resistor had quit as only the high speed setting would work, so we bought another one, installed it, switched it on - all 4 speed settings worked fine for the first 3 days after which - same as before only the high speed working. If the one fan speed is working - what is causing the others not to work?
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The first item with not enough heat may be your blend door. It may not be opening. You will have to check the cables and see if it is operating the door.

The second problem with the blower is your bearings. They need to be lubed or the blower will ruin the resistor block by drawing too much current.
http://www.focusfanatics.com/forum/showthread.php?t=245260
 

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The blend door is operated by the temperature selector. By turning the selector back and forth, you should hear the door opening and closing. The Focus does not have a heater valve like some cars...the door is used to simply allow air to flow through the heater core or not, or partially depending on the selection.
 

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"....worked fine for the first 3 days after which - same as before only the high speed working"

Your new resistor block has probably been ruined. You can check it with an ohmmeter. See if there is continuity between pin 1 and the other three pins. If there is no continuity the thermal fuse has been blown due to the dragging fan bearings.

A schematic of the fan circuit is in this thread:
http://www.focusfanatics.com/forum/showthread.php?t=329049

Speed 4 bypasses the resistor block and will continue to work even if the block is bad.

Be sure and check for junk (leaves and other trash) behind the evaporator coil while you have the blower motor out. Ford did not put a cabin filter in at the factory...just a placeholder for one under the cowling.
 

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Blender door working fine, air gets redirected appropriate to selector setting.
That is good news! If it was not working the repair could range from very simple all the way to having to tear the entire dash apart. Now to check the A/C bypass door per AMC's post.

As to resistor blocks and speed switches not working - both being electrical makes 'em beyond me, if either is the issue - it'll have to stay that way!
I understand. Troubleshooting electrical is difficult for many. However, you could turn this into just a mechanical repair by replacing the blower fan and resistor block.

If you don't replace the fan I predict additional problems will develop with it. As the fan bearings continue to dry out and the fan struggles more and more to run, it will eventually start blowing the fuse. Hopefully it won't burn any wiring. So, either make the repairs now or expect for it to stop running in the near future.

Cheers!
 

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I got to thinking about the A/C bypass door that is described above and I think that is the recirculation/fresh air door. I am not familiar with an A/C bypass door being there. If that is the case, then your heat should still work regardless of the position of that door.

If you are only getting warm air AND the blend door is working correctly...all the way from cool to hot on temperature selector switch...then I am leaning towards a plugged heater core.

When you had the flush done, you don't mention anything other than the radiator. Was the full system flushed or just the radiator? The heater core should be back-flushed and is not too hard to do.
 

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This post contains a fairly good description of how to test for a plugged heater core and how to clear it: http://www.focusfanatics.com/forum/showpost.php?p=4900826&postcount=15

Note that he had to rev the engine after he did his work. This is because the heater core is filled with air after you have completed the flush and that air is often not pushed out by the water pump at idle conditions. Revving the engine a couple of times will burp the core.
 

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Not to worry AMC!

I'm old and my brain cells are dying...sometimes I can't even keep my cars straight and I only have two to work on now that the kids are gone.

And the other thing that happens to me is that what I type is NOT what is in my head! Frustrating.........
 
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