Author Topic: heater blower motor blows fuse 1977 non a/c 2 wheel drive  (Read 505 times)

Offline buick

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heater blower motor blows fuse 1977 non a/c 2 wheel drive
« on: May 15, 2018, 06:47:41 PM »
1977 c10 non a/c ,have put in 3 new blower motors,2 switches,2 resisters,the blower works fine on low and mediam,runs like mad on high for about 5 min,then blows the fuse,installed 25 amp circuit breaker fuse in stead of regular fuse,turn off ign for a coupe of min and the same thing starts all over,dont wanna go through anter winter with only medium fan,should i put some kind of resister in the line to the blower motor?thanks for any input

Offline bd

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Re: heater blower motor blows fuse 1977 non a/c 2 wheel drive
« Reply #1 on: May 15, 2018, 07:34:51 PM »
Do you have a voltmeter?  Measure the voltage across the blower fuse (fuse clip-to-fuse clip) with the blower motor on the HIGH-speed setting.  What is it?
Rich
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In other words... if people learn by making mistakes, by now I should know just about everything!!
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Offline buick

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Re: heater blower motor blows fuse 1977 non a/c 2 wheel drive
« Reply #2 on: May 15, 2018, 08:52:11 PM »
what would that tell me?

Offline bd

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Re: heater blower motor blows fuse 1977 non a/c 2 wheel drive
« Reply #3 on: May 16, 2018, 01:19:02 AM »
Whether voltage is wasted across the fuse due to poor connections, which will concentrate heat in the fuse element, causing premature failure.
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline buick

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Re: heater blower motor blows fuse 1977 non a/c 2 wheel drive
« Reply #4 on: May 16, 2018, 06:05:40 AM »
i have a new circuit breaker fuse that i replaced the og fuse,the blower motor gets to hot to touch when it kills the circuit breaker,im wondering if i have a ground issue somewhere,ran a jumper from hole in he side of blower motor to batt ground wire with no change,in i use head lites,radio and turn signal at the same time it takes a couple more min for the breaker to fail,so that tels me im gettin to much amp,have no idea,unless the trucks is grounding through the blower motor run wire

Offline VileZambonie

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Re: heater blower motor blows fuse 1977 non a/c 2 wheel drive
« Reply #5 on: May 16, 2018, 06:24:36 AM »
Putting a circuit breaker in place of a fuse is a good way to ensure you'll find the problem with smoke. What fuse rating did you have in there to begin with?

Do you have a voltmeter?  Measure the voltage across the blower fuse (fuse clip-to-fuse clip) with the blower motor on the HIGH-speed setting.  What is it?

Do you have a voltmeter? If you follow bd's directions you will isolate the problem.
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Offline blazer74

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Re: heater blower motor blows fuse 1977 non a/c 2 wheel drive
« Reply #6 on: May 16, 2018, 10:28:40 AM »
I’ve had this happen except would take longer to blow the fuse.

Mine was with A/C but would do it with just heat also.

Ended up being a loose terminal in the connector at the controls.

Offline buick

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Re: heater blower motor blows fuse 1977 non a/c 2 wheel drive
« Reply #7 on: May 16, 2018, 01:58:10 PM »
im handicapped and unable to do voltage tests etc,a friemd replaced a 25 amp fuse with a 25 ampcircuit breaker,i ran it a while ago with the eng off,worked for 5 min,as soon as i swichted it to med it blew the breaker,my dash volt meter runs right at the high yellow witch would be about 15.5 volts,i would like to run direct from another battery to see if it works,on high with the engine running the blower motor gets to hot so it must be gettin to much current somehow,gotta let it rest awhile,driving me crazy,been workin on cars for 55 years and this one doesnt add up

Offline VileZambonie

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Re: heater blower motor blows fuse 1977 non a/c 2 wheel drive
« Reply #8 on: May 16, 2018, 05:34:29 PM »
Unfortunately without a meter you are going to continue loading the parts cannon and have to guess.

The circuit uses a 20 Amp fuse, not a 25 and not a circuit breaker. Overloading the circuit will result in a fire so you need to be very careful.

Unplug the resistor and see if it still blows a 20 amp fuse on high.
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Offline buick

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Re: heater blower motor blows fuse 1977 non a/c 2 wheel drive
« Reply #9 on: May 16, 2018, 10:36:35 PM »
it kept blowing fuses,thats why we put the cb in there,tired of changing fuses,you wont have a fire with a cb,and it calls for a 25 fuse to begun with,now works ok with engine not running and key on

Offline Captain Swampy

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Re: heater blower motor blows fuse 1977 non a/c 2 wheel drive
« Reply #10 on: May 22, 2018, 10:36:37 AM »
Maybe the voltage regulator. Vile and BD are very sharp. If you follow their instructions, you will solve your problem quickly with out spending extra money.
« Last Edit: May 22, 2018, 10:40:45 AM by Captain Swampy »
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Offline buick

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Re: heater blower motor blows fuse 1977 non a/c 2 wheel drive
« Reply #11 on: May 22, 2018, 06:55:51 PM »
you mean the regulator in the alternator?cause thaes what i thought,i can run straight from the battery and the blower motor doesnt overheat or blow the fuse

Offline buick

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Re: heater blower motor blows fuse 1977 non a/c 2 wheel drive
« Reply #12 on: May 27, 2018, 05:19:20 PM »
my fuse checks out ok,on high motor still runs till its hot and then pops the fuse,in my setup the truck runs full 12 volts,no resistor,o ohms from heater motor to firewall so it mus be grounded,any ideas?thanks

Offline buick

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Re: heater blower motor blows fuse 1977 non a/c 2 wheel drive
« Reply #13 on: May 27, 2018, 07:49:32 PM »
soulg my 77 gmc 2 wd non a/ have a vented blower motor?thanks

Offline buick

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Re: heater blower motor blows fuse 1977 non a/c 2 wheel drive
« Reply #14 on: May 28, 2018, 10:16:13 AM »
ya mean nobody here has a non air truck and cant look to see if their heater mtr has a vent tube on it?