HELP! 84 BUICK REGAL LIMITED

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Steve84

Apprentice
Jul 8, 2018
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17
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#1
Hi all, my name is Steve. I am new to the forum. I have an '84 Buick Regal Limited as a daily driver with the V6. Today my blower motor fan shut down when I went to turn on the A/C. Again the GROUND wire terminal end on the PCB block (printed circuit assembly board that goes inside the blower housing for the automatic climate control) burnt. It happened once before years ago, but this time it was real bad. So I had to splice in a new spade connector.
Just so everyone knows, these automatic climate control types have a UNIQUE circuit board ** assembly that has a few transistors caps, resistors ground plate etc. They are not like normal ones. They don't even sell these anywhere that I could find. This board senses the temperature of the heater core so the heat starts blowing in AUTO mode once the heater core gets up to temperature. Thank God it seems the board assembly is still good.

Now when I repaired the burnt end, I was smart enough this time to put a in-line fuse to this ground terminal. I have a 10 amp fuse in it. So I went to use the A/C and it started to blow and then shut down. I believe the fuse has blown.

I have two questions?

Is the 10 amp fuse proper for a blower motor or is it too low of amps?

My next question, is that I'm afraid to put a higher one in, because I don't want to burn the wire again. Is it possible that the blower motor has a short in it? And is why the wire burnt in the first place from drawing too much current? I think this is the original motor from '84 because I bought the car in '97 with only 70,000 miles on it and had it ever since. Can someone please help so I know what fuse to use and IF I should replace the blower motor? Thanks

PS ** the Printed circuit board where the burnt ground terminal is - is called the
HEATER SPEED CONTROL RESISTOR which is different than a normal type for manual controls. Mine has more terminal and components on it.
 
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fleming442

fleming442

Comic Book Super Hero
Dec 26, 2013
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#2
I'd start with a blower motor, and yes, 10A is probably a little light for the load. It probably draws at least that and more if the bearings are bad or the grease is sticky from age.
BUT, the blower motor has it's own ground, so that isn't your problem......
 
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S

Steve84

Apprentice
Jul 8, 2018
60
17
8
#3
I'd start with a blower motor, and yes, 10A is probably a little light for the load. It probably draws at least that and more if the bearings are bad or the grease is sticky from age.
BUT, the blower motor has it's own ground, so that isn't your problem......
I thought that the circuit board regulates on/off and speed of blower motor so the power must run through it. Isn't the motor still drawing power THROUGH the speed control module? Which means the current draw in excess would burn the ground terminal on module first before the motor ground. To my knowledge a GROUND will burn at its weakest point in a circuit and the blower speed module pcb has the weakest ground compared the the blower motor which has much more substantial metal surface area for a greater ground. I checked all components on pcb to ground and nothing is short.

I will replace blower motor this weekend. What would be proper fuse - 20 amp?
 
foxtrot

foxtrot

Royal Smart Person
Dec 19, 2008
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#4
Welcome to the forum.

You could always 'bench test' the blower motor to verify proper operation and to determine the nominal current flow. Once you have determined the nominal current flow with the blower operating on high speed, I would install an in-line fuse that is %10 larger than the nominal measured current.
 
foxtrot

foxtrot

Royal Smart Person
Dec 19, 2008
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#5
These diagrams may be of some help:
http://www.maliburacing.com/wiring.html

Also, in the past when I've found the blower wire melted like you described, it's typically caused by a bad connection. IE: a connection with higher than normal resistance with a larger voltage drop.
 
S

Steve84

Apprentice
Jul 8, 2018
60
17
8
#6
Welcome to the forum.

You could always 'bench test' the blower motor to verify proper operation and to determine the nominal current flow. Once you have determined the nominal current flow with the blower operating on high speed, I would install an in-line fuse that is %10 larger than the nominal measured current.
That makes sense. The only thing I could think of is that when a motor first starts up it draws the most current. Once running the current drops and stabilizes. I could put an amp meter between and see the current draw, But I don't know what PROPER DRAW is for these motors. It is the original from 1983 when car was built. I read in other places that blower motors that are old tend to draw excessive current and end up burning out speed control modules.
 
foxtrot

foxtrot

Royal Smart Person
Dec 19, 2008
1,475
536
83
USA
#8
That makes sense. The only thing I could think of is that when a motor first starts up it draws the most current. Once running the current drops and stabilizes. I could put an amp meter between and see the current draw, But I don't know what PROPER DRAW is for these motors. It is the original from 1983 when car was built. I read in other places that blower motors that are old tend to draw excessive current and end up burning out speed control modules.
I'm not sure of the current spec either but I'm sure some of the other guys with factory service manuals could chime in.

The blower motor does have a greater startup current over the nominal current.
 
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Steve84

Apprentice
Jul 8, 2018
60
17
8
#9
I'm not sure of the current spec either but I'm sure some of the other guys with factory service manuals could chime in.

The blower motor does have a greater startup current over the nominal current.
Did you ever see a speed module for a Limited with the soft touch climate control? It is not just coiled wires like most with with 5 terminals. Mine is long and has a ground plate with a large metal cased transistor, other transistors or regulators, resistors, caps, and 7 terminals. Where could I ever get a replacement if ever needed?
 
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Steve84

Apprentice
Jul 8, 2018
60
17
8
#10
Did you ever see a speed module for a Limited with the soft touch climate control? It is not just coiled wires like most with with 5 terminals. Mine is long and has a ground plate with a large metal cased transistor, other transistors or regulators, resistors, caps, and 7 terminals. Where could I ever get a replacement if ever needed?

Also since current flows out of ground (-) and into positive (+).... This would mean that the power drawn by motor is pulling current from and through the speed control module first that supplies the power and that is the ground that got burnt which makes sense. Correct?
 

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