blower does low speed only
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blower does low speed only
Well,
The '01 350 passed state inspection today(after replacing the front tires), but while I was driving it around with the AC on I discovered that the blower will only operate at low speed. No matter where I put the the selector switch I only get low speed.
I have searched on this subject and have observed that this can possibly be fixed with replacing the resister. However I also have seen that if the resister fails that the fan will only operate in high speed. This has left me confused.
is it worth pulling out the resister? Is there anything else I should check?
All suggestions are apreciated.
Thanks,
skip
The '01 350 passed state inspection today(after replacing the front tires), but while I was driving it around with the AC on I discovered that the blower will only operate at low speed. No matter where I put the the selector switch I only get low speed.
I have searched on this subject and have observed that this can possibly be fixed with replacing the resister. However I also have seen that if the resister fails that the fan will only operate in high speed. This has left me confused.
is it worth pulling out the resister? Is there anything else I should check?
All suggestions are apreciated.
Thanks,
skip
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Does anyone have a clue on the low speed fan problem before I dig into it? The weather is getting hot and I need to fix it.
Should I begin by removing the resistor?
Any and all advice is appreciated.
Thanks,
Skip
Should I begin by removing the resistor?
Any and all advice is appreciated.
Thanks,
Skip
Fleet Mechanic
Joined: May 2005
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From: Puyallup, WA
Skip, normaly the resistor is only for the lower speeds, the high speed setting on a A/C equiped truck normally goes thru a relay. Have you traced back the fan wire a bit and see if it ties into any square boxes, IE relay?
I can't however say for sure as I don't have any Ford Factory Van manuals / wiring diagrams to check.
Hopefully someone else will weigh in with the absolute authoritive answer here.
David
I can't however say for sure as I don't have any Ford Factory Van manuals / wiring diagrams to check.
Hopefully someone else will weigh in with the absolute authoritive answer here.
David
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Thanks for the info David,
The owners manual shows both the blower motor fuse and relay are located in thr engine compartment fuse box. The fuse is identified as #13 and the relay as 'H'.
If the relay fails will there be any fan speed at all? I do have low speed - same as in its lowest position- since the fan cannot be completely tirned off.
Does low speed go through a different route?
Thanks.
Skip
The owners manual shows both the blower motor fuse and relay are located in thr engine compartment fuse box. The fuse is identified as #13 and the relay as 'H'.
If the relay fails will there be any fan speed at all? I do have low speed - same as in its lowest position- since the fan cannot be completely tirned off.
Does low speed go through a different route?
Thanks.
Skip
Fleet Mechanic
Joined: May 2005
Posts: 1,575
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From: Puyallup, WA
Skip, Generaly you wil have the lower speeds when the relay fails, it is only used normally for the "highest" setting, where the amperage draw is the greatest.
Low speeds and the power to energize the relay go thru the fuse, but only to energize the relay, the actual high amperage power that the relay "switches" to the blower motor comes from a different source.
The resistor is not used at all on the high setting, you get full avalible voltage to the blower motor.
David
Low speeds and the power to energize the relay go thru the fuse, but only to energize the relay, the actual high amperage power that the relay "switches" to the blower motor comes from a different source.
The resistor is not used at all on the high setting, you get full avalible voltage to the blower motor.
David
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I will check the relay tomorrow. I have located the power distribution box but am unable to open it by flashlight.
David - you indicated that the resistor handles the lower speeds. I only have 1 speed - the lowest- no matter where the switch is positioned.
Is this consistant with a bad relay?
thanks,
Skip
David - you indicated that the resistor handles the lower speeds. I only have 1 speed - the lowest- no matter where the switch is positioned.
Is this consistant with a bad relay?
thanks,
Skip
Fleet Mechanic
Joined: May 2005
Posts: 1,575
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From: Puyallup, WA
Skip, Normally I would expect to see the two lowest speeds (three total speeds), or three if you have four different speeds. This is where I would like to see a factory wiring diagram.
I have not seen a system yet where all the fan speeds are run thru the relay though. I really wish I could help you with a absolute here.
David
I have not seen a system yet where all the fan speeds are run thru the relay though. I really wish I could help you with a absolute here.
David
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I was just now looking in the Haynes manual I have for the E350 and found the following in section 3-9:
"NOTE: .... There are three resistor elements mounted on the resistor board to provide medium low, medium high, and high blower speeds (LOW bypasses the resistor...."
the note continues referring to a thermal limiter resistor
This leads me to beleive that the relay or the thermal limiter resistor has failed. I will have a fun time digging into this.
I will report the results.
Thanks,
Skip
"NOTE: .... There are three resistor elements mounted on the resistor board to provide medium low, medium high, and high blower speeds (LOW bypasses the resistor...."
the note continues referring to a thermal limiter resistor
This leads me to beleive that the relay or the thermal limiter resistor has failed. I will have a fun time digging into this.
I will report the results.
Thanks,
Skip
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success
After checking and eliminating the fuse, relay, resistor, blower motor and wiring. The only thing left to check was the switch.
I pulled back the dash trim amd removed the Hat/AC/fan switch assembly.
The wire connector at the blower switch appeared melted and disformed. When removing the connector, the back of the switch was melted and burnt. apparently an internal short caused the plastic to melt so the contacts would not contact.
A trip to the dealer, a new switch, and all fan speeds now work.
- Skip
I pulled back the dash trim amd removed the Hat/AC/fan switch assembly.
The wire connector at the blower switch appeared melted and disformed. When removing the connector, the back of the switch was melted and burnt. apparently an internal short caused the plastic to melt so the contacts would not contact.
A trip to the dealer, a new switch, and all fan speeds now work.
- Skip
Elder User
Joined: May 2007
Posts: 754
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From: Solon, Ohio
It wasn't actually a short that caused the switch to burn, but an open.
High resistance do to poor or worn switch contacts in the high speed position caused the heat.
A bad blower motor that draws too much current can also cause this.
High resistance do to poor or worn switch contacts in the high speed position caused the heat.
A bad blower motor that draws too much current can also cause this.
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