Heater Hi not Full Fan Speed - Ford Bronco Forum
 
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post #1 of 9 (permalink) Old 10-16-2016, 05:12 PM Thread Starter
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Heater Hi not Full Fan Speed

Howdy all, searched a bunch and found tons on the resistor but I've got a different issue and the -20 is on its way!

86 XLT with air.

I get low, m1 and m2 but when switching to high the fan speed drops down.

I've replaced the resistor. I get full fan when direct from battery to fan plug. I get full fan when jumping the resistor connectors to the ground resistor connectors.

I assume I am not getting full voltage to the fan when the switch is on high. I understand that the high setting bypasses the resistor. I'm not sure of what is between the dash switch and the fan, I assume there must be a relay somewhere and not 10g wire from the bat to switch to fan.

Ideas and experience?

Thanks!


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post #2 of 9 (permalink) Old 10-16-2016, 05:35 PM
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Has happened to me before, but in an Explorer. The easiest solution for me was to replace the blower motor.
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post #3 of 9 (permalink) Old 10-16-2016, 05:57 PM Thread Starter
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Thanks hms but the blower motor works 100% when full 12v is applied. Has to be somewhere between the motor switch battery


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post #4 of 9 (permalink) Old 10-16-2016, 06:04 PM
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Well, that's good. Is it a replacement motor? I have found them to be cheap poo! Any how, that was my experience. I'm not much on electrical stuff.
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post #5 of 9 (permalink) Old 10-16-2016, 06:46 PM Thread Starter
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It's a motorcraft blower so I think it's original


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post #6 of 9 (permalink) Old 10-17-2016, 01:45 PM
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Yo biggum,
Bad brain day now.. so reading all this and responses have me in stupor.


Quote:
Originally Posted by biggum View Post
I get low, m1 and m2 but when switching to high the fan speed drops down.
I've replaced the resistor. I get full fan when direct from battery to fan plug.
So blower motor is ok.

I get full fan when jumping the resistor connectors to the ground resistor connectors.
Ok, that section of wiring is ok as well as the ground.

I assume I am not getting full voltage to the fan when the switch is on high. I understand that the high setting bypasses the resistor. I'm not sure of what is between the dash switch and the fan, I assume there must be a relay somewhere and not 10g wire from the bat to switch to fan.
The high speed setting bypasses the blower motor resistor pack (see the diagram below). There is no relay.
Check switch connector and blower motor connectors for corrosion, etc.
Some are known to overheat and melt the plastic housing.

Wiring Diagram in an 86 Bronco & F-Series

See my partially recovered Bronco web site ...Will need to clean up dead links & add many more new links some day. Thanks to Mr. Schwim!
THANKS to ALL WHO SERVE!
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post #7 of 9 (permalink) Old 10-17-2016, 03:19 PM
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What miesk5 said

1988 Full Size Bronco, 5.0, AOD, Manual transfer case
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post #8 of 9 (permalink) Old 10-17-2016, 07:54 PM Thread Starter
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Thanks guys, I'm leaning towards the switch being bad or possibly a ground issue.


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post #9 of 9 (permalink) Old 03-20-2017, 05:43 PM Thread Starter
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To close this out.....the dash switch was bad - partially melted. Put in a new switch and works great. Did a little research and apparently melted heater fan switch is fairly common Ford issue. Cheers


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