Blower Motor
Laughing Gas
Joined: Dec 2000
Posts: 780
Likes: 18
From: East Texas
Blower Motor
I originally posted this in the heating/air conditioning forum but didn't get any replys. Perhaps I'm just way off base, but maybe someone can provide some insight.
I have a 1977 F-250 w/351M, 4-Speed, no air. I have seen some information regarding a high output heater option on these trucks. My heater makes warm air but the problem seems to be not enough air flow/volume. I replaced the heater core last year and cleaned out the ducting. My question is, was there a high output option and if so, could a blower from this application be used in the standard heater setup.
Thanks for your help.
Jason
1993 F-150 300 I-6 w/5-Spd.
1977 F-250 351m w/4-Spd.
I have a 1977 F-250 w/351M, 4-Speed, no air. I have seen some information regarding a high output heater option on these trucks. My heater makes warm air but the problem seems to be not enough air flow/volume. I replaced the heater core last year and cleaned out the ducting. My question is, was there a high output option and if so, could a blower from this application be used in the standard heater setup.
Thanks for your help.
Jason
1993 F-150 300 I-6 w/5-Spd.
1977 F-250 351m w/4-Spd.
Posting Guru
Joined: Aug 2002
Posts: 1,214
Likes: 2
From: Minneapolis, MN
Blower Motor
Jason, I think the difference in the High Output Heater option was in the size of the heater core, larger core = more heat. I don't know if the blower motors were different.
Just my $.02
Greg
'77 F-250 Camper Special 400ci driver
'76 F-250 Supercab 360ci current project
'71 Mach I 429CJ in storage
'79 F-150 for parts
HONK if you love peace and quiet!
Just my $.02
Greg
'77 F-250 Camper Special 400ci driver
'76 F-250 Supercab 360ci current project
'71 Mach I 429CJ in storage
'79 F-150 for parts
HONK if you love peace and quiet!
Junior User
Joined: Jan 2003
Posts: 50
Likes: 0
From: Billings USA
Blower Motor
Jason,I have a 79 and when I went to the local Napa they asked me if it was H.O. or not?I didn't know but the parts guy did tell me there was a definite size differential and that the larger one wouldn't fit if not equipped.He couldn't give me dimensions. John
Cross-Country
Joined: Jan 2003
Posts: 83
Likes: 0
From: Lafayette, La
Blower Motor
I have a 79 F150 w/air and I had the same problem. During the coldest part of the winter I would run 12v directly to the motor. It would put out alot more air than usual. Measure the voltage at the motor with a multimeter and see how many volts you actually have. The wiring diagrams I have seen show that on "High" there is supposed to be a full 12v at the motor but I only had 10 volts. As the switches and wiring gets older they build up resisitance causing a loss in voltage. You might be able to replace your switch and that might help. I never tried it on my truck because back when it was my daily driver I didn't know diddly about electronics. After a couple of years at a tech school I know a little more now.
By the way in 77 there was a high output heater for sure, my uncles truck had one. I don't know what the difference between High Output and the regular heater is though.
Good luck
By the way in 77 there was a high output heater for sure, my uncles truck had one. I don't know what the difference between High Output and the regular heater is though.
Good luck
Thread Starter
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Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
Blower Motor
If you have low voltage at the motor you may want to check some of your connections. Those voltage drops are how fires start...
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Laughing Gas
Joined: Dec 2000
Posts: 780
Likes: 18
From: East Texas
Blower Motor
Yeah, the low voltage as well as the switch have crossed my mind. It's possible that it could be the switch as one of the settings stopped working within a year after my dad bought it in 1977. I've been holding off on replacing it as I will be replacing the instrument panel back plate and will replace the switch then. No need to take the panel apart twice if I can avoid it. I will be checking the voltage to the motor as well.
Thanks for all your help.
Jason
1993 F-150 300 I-6 w/5-Spd.
1977 F-250 351M w/4-Spd.
Thanks for all your help.
Jason
1993 F-150 300 I-6 w/5-Spd.
1977 F-250 351M w/4-Spd.
Trending Topics
Posting Guru
Joined: Jul 2001
Posts: 1,613
Likes: 2
From: Gainesville, FL
Blower Motor
All,
I am not sure but:
The switch is not the magic device controlling the speed of the fan.
There is a resistor assembly that mounts in the ductwork which causes the voltage drop.
As the years pass, and beleive me they are passing, the resistors start to corrode and the voltage to the blower motor starts to drop. Replace this assembly and you should be good to go. When you find it it should be mounted in the duct and have three coil-like resistors.
Has anybody seen this assembly before?
It seems like 10 years since I've had to screw with that thing.
Chime in, I could be wrong, unlikely, but possible.
KingFisher
I am not sure but:
The switch is not the magic device controlling the speed of the fan.
There is a resistor assembly that mounts in the ductwork which causes the voltage drop.
As the years pass, and beleive me they are passing, the resistors start to corrode and the voltage to the blower motor starts to drop. Replace this assembly and you should be good to go. When you find it it should be mounted in the duct and have three coil-like resistors.
Has anybody seen this assembly before?
It seems like 10 years since I've had to screw with that thing.
Chime in, I could be wrong, unlikely, but possible.
KingFisher
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Elder User
Joined: Oct 2002
Posts: 654
Likes: 0
From: Seattle/Tacoma Washington U.S.A.
Blower Motor
A larger Heater core would not solve your problem, it might even make things worse, JC whitney makes high output heater cores that are the same size as stock, and blower motors are dirt cheap... Go to a wrecking yard or buy a new one if you still have the problem after you test the wires, connections/connectors, and switches. good luck.
Elder User
Joined: Dec 2002
Posts: 925
Likes: 0
From: Quaker Hill ,CT U.S.A.
Blower Motor
Find a heater box system out of a '78-'79 ford bronco they come with a highoutput heater and will fry you out of the truck. Before you install the new sysem install a new heater core and blower motor so that you dont havee to remove it again
Jon
'75 F100 4X4 5.9
'89 F150 4X4 4.9
Jon
'75 F100 4X4 5.9
'89 F150 4X4 4.9
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