Replace heater/AC blower motor/fan
Instructor
Joined: Jul 2011
Posts: 142
Likes: 1
From: Fort White Florida
I finally got my AC working again had to replace the Control Assembly. It had quit working in September then it cooled off so I moved repairing down the list. I noticed that the blower wasn't all that strong (have only had my '79 since July) so I did a search on here and found this thread. I gave the 12 gauge wire ground trick a try. I attached the wire to my compressor bracket and sure enough it almost doubled the blower speed. Just wanted to say thanks to those who posted the info.
Intermediate
Joined: Aug 2011
Posts: 32
Likes: 0
From: Ottawa Ontario
I have to say you folks are saviors! The fan in my 72 coupe has never blown well. I was considering changing out the blower motor and squirrel cage to a C4 (which sounds like a real PITA) but decided to try the short cut of changing out the grounding wire. Makes sense since amps in equals amps out the larger gauge wire should help but... Unfreaking believeable it worked like a charm. The blower works like the fan in my modern car. In the spirit of the KISS principle...Thanks, you guys rock!
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Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
When current (not voltage) passes through a wire some of the energy (voltage) is used up just to get the current to traverse the wire itself. This is called an "I-squared R loss". Mathematically... power(W)=volts(E)* current(I) or W=EI. Ohms law.. voltage(E)=current(I)* resistance(R). E=IR. Substitue IR for E in W=EI and you get W=IRI or W= I-squared R. This is a measure of the power lost just in the ground wire. The resistance "R" is lower for a larger cross-sectional wire. The bigger the wire, the lower it's resistance. So... when you lower the resistance by installing a bigger diameter wire, the "I-squared R" power loss across the blower motor ground wire goes down, and there is more power available for the motor to use. That is... the voltage drop across the ground wire is less with a bigger diameter ground wire so there is more voltage available at the motor, and since it's a DC motor, the higher voltage means it spins faster. Another every day example would be an electric weed-whacker... plug it directly into an outlet and watch it work. Now plug it into a 200 foot extension chord and watch it not work so well. This is due to the I-squared R loss in the extension chord.
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
In my opinion... and this is only an opinion... the motors should have been designed by GM to run on 12(battery)-14(charging) volts... not 10-11 volts. So... the motor should be fine with a better ground. In many cases, when you operate certain motors at less than their designed optimal voltage, they tend to heat up and their life expectancy goes down. I will be installing a bigger ground wire in my 70 since my blower motor runs slow. I don't expect any collateral damage.
Racer
Joined: Jan 2015
Posts: 314
Likes: 50
From: Woodbury NJ
I realize this is an old thread, but two things:
1. Has anyone used a 3-D printer to this or any other part yet?
2. Big shout out thank you for the electrical education on both current/resisitance AND underscoring the need to beef up grounds during our restorations.
This thread is a real time saver; thanks again to everyone who participated.
1. Has anyone used a 3-D printer to this or any other part yet?
2. Big shout out thank you for the electrical education on both current/resisitance AND underscoring the need to beef up grounds during our restorations.
This thread is a real time saver; thanks again to everyone who participated.
