Mechanics

BLOWER FUSE / DEFROST SETTING

1999 Ford Contour

Heater problem
1999 Ford Contour 4 cyl Two Wheel Drive Automatic

The interior compartment fuse for the heater blower " blows" when I turn the fan setting to either floor/defrost or defrost. Te fan will operate normally if I keep it away from the defrost setting. I should mention that the air conditioner has been removed from the system.

Can only get air flow when not in the defrost setting. Youcan actually hear stress on the engine when the defrost blower setting is selected before the fuse blows.

Any suggestions on where my short is?

Phil
Avatar
Aheise@new.rr.com
September 25, 2010.



Hi Phil,

Thank you for the donation.

The defrost and floor modes are controlled by actuator vacumn motor.

Check around the actuator vacuum motor for wires that are being grounded when the mode door moves. A wire could be exposed due to abrasion causing the shorting.

KHLow2008
Sep 25, 2010.
Thanks for your advice. Got any more? Looked everywhere for shorted wires and found nothing. I should mention that this all started with the control not being able to switch to the defrost setting. It is just receintly that the fuse started blowing.

I did try to replace the main control but no luck. Anyone have any suggestions? I have to get the car back to my son and I am running out of ideas.

Phil

Tiny
Aheise@new.rr.com
Oct 1, 2010.
Sorry, I need some clarification.

Your first post mentioned that problem occurred when the setting was turned to defrost.

2nd post indicated you were not able to turn control to defrost setting.

Can you please elaborate on the 2 statements?

Do you mean you have replaced the control and it did not help?

What is the EXACT fuse that is blowing? Location or name on the cover would help.

KHLow2008
Oct 2, 2010.
Hi - thanks for your response. I can change the switch to any of the desired fan settings. It is only when I turn the switch to " floor/defrost" or " defrost that the fuse blows. (Fuse #37, interior pannel, labled " heater blower motor.)

I did replace the control pannel switches but it had no effect. I can set the fan to any speed with no problems. It is only when the defrost setting is selected that the fuse blows. Hope this clears it up.

Phil

Tiny
Aheise@new.rr.com
Oct 2, 2010.
This is strange. Fuse # 37 is solely for the use of the blower motor fan, fan speed and relay and not related to the heater mode switch.


http://www.2carpros.com/forum/automotive_pictures/192750_HeaterWiringContour99Fig02a_1.jpg



http://www.2carpros.com/forum/automotive_pictures/192750_HeaterWiringContour99Fig02b_1.jpg



For the fuse to be shorting out, it should be a fault between the fuse and blower fan motor. What is surprising is why it is not doing so in other modes.

Is the correct fuse used? ( 30 A).
Does it blow immediately upon turning to defrost or it takes some time to do so?

KHLow2008
Oct 3, 2010.
Tell me about it! I've never been stumped electricaly before this. The fuse blows about 20-30 seconds after the defrost setting is selected. The weird thing is that if I unplug the fan and turn the switch to defrost, it will still blow with no load to it. I attached and ohm meter to the pigtail that connects to the fan and in all setings there is no resistance eccept when I turn to the defrost setting and then I get about 500Killo ohms of resistance. Yes - I am useing the correct fuse - 30 amp.

Tiny
Aheise@new.rr.com
Oct 4, 2010.
The defrost setting seems to have caused something to short out the circuit but based on the wiring diagram, it should not occur, unless the wiring schematic is wrong.

I am going to post this in the moderators forum to get my fellow technicians to have a look into this and see if any of them can come up with anything.

KHLow2008
Oct 4, 2010.
Does it blow when the knob is turned to max or regular ac?

One thing you can opt to do is take the back off of a fuse and solder in a auto headlight to the top of the and brake the internal part that way all current flows through the bulb. From there watch the intensity of the light bulb in all positions what do you find in each setting get them back to me.

Also as I suspect the light may get brighter in the defrost position if it does start wiggling the wires on the back of the control unit and blower door actuators expecially the defrost one and see if bulb gets dimmer.

Blackop555
Oct 4, 2010.
The fuse doesnt blow when in any of the ac settings - only floor/defrost, and defrost. The bulb gets dimmer when turned to defrost setting. It actually slowly gets dimmer then out when the fuse blows.

Tiny
Aheise@new.rr.com
Oct 4, 2010.
Cant you hook the bulb up in place of a fuse so the bulb stays on all the time. We need to have this so we can find the location of the problem without second guessing everything.

You can use a circuit breaker fuse but its slower to find. And harder to listen

Blackop555
Oct 4, 2010.
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