Re: defroster/heater motor
Posted by HH56 On 2012/7/16 10:26:18
If your car has this same type defroster/foot warmer as my 47 and all air is directed to defrost, then it's air flow is fairly robust -- although nothing like a new car.
I tried a couple of defroster units I had and one did run faster than the other. First thing to look at is the ground. It appears to be supplied by the two mounting bolts and as you can see on this one, dirt, corrosion, rust etc can really mess things up. On the slower one, I played around and cleaned the stud where the ground connection was being made. With a better ground, it did run faster and outputs finally matched fairly well.
My heater and defroster switches look like this one. If the switch does turn out to be a problem or resistance connections are corroded or loose under the connecting rivets, not sure how much can be done without proper equipment. The ceramic is delicate and can break if much force is applied in the wrong place. Maybe some contact cleaner will help. At any rate, when I first took the switches apart they were pretty bad inside so maybe cleaning the switch itself would help. If the problem is with the connections, there is a company that rebuilds switches so would probably have the tools and expertise to redo the rivet connections safely.
Did a few electrical checks and while not the most scientific methods, results might give a starting point to determine if the switch is the problem or if motor is sluggish and needs work.
No 6v battery was available so used my 50 amp charger. Output was 7.1v. Both units were drawing about 5-7 amps at high speed.
First notch or High delivered 7.01v to motor so approx .1v drop in switch.
Second notch or Med delivered 5.80v. The resistance unit is too low to measure accurately with my meter but think it is about .5 ohm at that point.
Third notch or Low delivered 4.60v and am thinking total resistance is 1.0 ohm.
Using a regular 6.3 volt battery will have slightly less volts but still proportional.
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I tried a couple of defroster units I had and one did run faster than the other. First thing to look at is the ground. It appears to be supplied by the two mounting bolts and as you can see on this one, dirt, corrosion, rust etc can really mess things up. On the slower one, I played around and cleaned the stud where the ground connection was being made. With a better ground, it did run faster and outputs finally matched fairly well.
My heater and defroster switches look like this one. If the switch does turn out to be a problem or resistance connections are corroded or loose under the connecting rivets, not sure how much can be done without proper equipment. The ceramic is delicate and can break if much force is applied in the wrong place. Maybe some contact cleaner will help. At any rate, when I first took the switches apart they were pretty bad inside so maybe cleaning the switch itself would help. If the problem is with the connections, there is a company that rebuilds switches so would probably have the tools and expertise to redo the rivet connections safely.
Did a few electrical checks and while not the most scientific methods, results might give a starting point to determine if the switch is the problem or if motor is sluggish and needs work.
No 6v battery was available so used my 50 amp charger. Output was 7.1v. Both units were drawing about 5-7 amps at high speed.
First notch or High delivered 7.01v to motor so approx .1v drop in switch.
Second notch or Med delivered 5.80v. The resistance unit is too low to measure accurately with my meter but think it is about .5 ohm at that point.
Third notch or Low delivered 4.60v and am thinking total resistance is 1.0 ohm.
Using a regular 6.3 volt battery will have slightly less volts but still proportional.
Attach file:
(65.16 KB)
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