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Discussion Starter · #1 ·
The high speeding setting on my a/c blower doesn’t work. The fan functions find at all other speeds. The a/c seems to be ok too. The fan switch felt hot after running the car for a while, so I pulled it and found there was a continuity problem with the high speed terminals. Replaced switch, same problem. Any thoughts?
 

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The high speeding setting on my a/c blower doesn’t work. The fan functions find at all other speeds. The a/c seems to be okay too. The fan switch felt hot after running the car for a while, so I pulled it and found there was a continuity problem with the high speed terminals. Replaced switch, same problem. Any thoughts?
The light duty fan speed switch operates the relay which then supplies power to the blower. The relay (mounted on the top of the evaporator housing) can usually be repaired by pulling a double sided (folded) piece of 600 grit wet-or-dry sand paper through its contacts. Also it's common for the 1/4" blade terminals in the relay connection to get burned because of the high amperage it carries.
 

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Discussion Starter · #3 ·
The light duty fan speed switch operates the relay which then supplies power to the blower. The relay (mounted on the top of the evaporator housing) can usually be repaired by pulling a double sided (folded) piece of 600 grit wet-or-dry sand paper through its contacts. Also it's common for the 1/4" blade terminals in the relay connection to get burned because of the high amperage it carries.
Thanks. I'll check that out. I did get the fan to blow on high when I bypassed the relay.
 

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Discussion Starter · #4 ·
Thanks. I'll check that out. I did get the fan to blow on high when I bypassed the relay.
I cleaned the connections as suggested. I also pulled the cover of the relay, found the wire from the windings to the #5 pin had broken. Made a repair. Still have low, med 1 and med 2, but hi speed. Any additions thoughts or suggestions?
 

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I cleaned the connections as suggested. I also pulled the cover of the relay, found the wire from the windings to the #5 pin had broken. Made a repair. Still have low, med 1 and med 2, but hi speed. Any additions thoughts or suggestions?
Did you sand the relay's contacts? The fan only has three speeds; low, medium, and high. The first two speeds are controlled by the resistors that extend into the blower housing and the HIGH speed bypasses those resistors.
 

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Discussion Starter · #6 ·
Did you sand the relay's contacts? The fan only has three speeds; low, medium, and high. The first two speeds are controlled by the resistors that extend into the blower housing and the HIGH speed bypasses those resistors.
I did sand the connectors. Also, the relay is only a year old.. My diagram showed 4 speed speeds. I appreciate the help.
 

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I did sand the connectors. Also, the relay is only a year old.. My diagram showed 4 speed speeds. I appreciate the help.
Yeah, I am probably wrong on the number of speeds. I leave mine on HIGH almost all the time because almost all of my trips are very short. I haven't taken my relay apart for a year or so but I seem to remember the contact has two positions; the default position and the energized position.
 

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Discussion Starter · #8 ·
Yeah, I am probably wrong on the number of speeds. I leave mine on HIGH almost all the time because almost all of my trips are very short. I haven't taken my relay apart for a year or so but I seem to remember the contact has two positions; the default position and the energized position.
I think I'll check the relay again. It may be shot, even though fairly new. If I bypass it and run power straight to the fan it runs on high.Thanks again.
 

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I think I'll check the relay again. It may be shot, even though fairly new. If I bypass it and run power straight to the fan it runs on high.Thanks again.
My plastic relay connection burned up long before I bought my '71. I just removed the wires and plugged them directly onto the relay's terminals. I found every brand of relay only lasts about one year before I have to sand the points so I now keep a new or reconditioned relay in stock. When they fail the blower won't shut off unless I tap on it to break the points loose. Just one of those annoying C3 problems that we learn to deal with. By the way, I have found the very best relays come from Standard Motor Products :

 

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Discussion Starter · #10 ·
My plastic relay connection burned up long before I bought my '71. I just removed the wires and plugged them directly onto the relay's terminals. I found every brand of relay only lasts about one year before I have to sand the points so I now keep a new or reconditioned relay in stock. When they fail the blower won't shut off unless I tap on it to break the points loose. Just one of those annoying C3 problems that we learn to deal with. By the way, I have found the very best relays come from Standard Motor Products :

I'm going to order a couple of relays from Standard Motor Products. IS it possible the fan motor is starting to fill, drawing too many amps?
 

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I'm going to order a couple of relays from Standard Motor Products. IS it possible the fan motor is starting to fill, drawing too many amps?
I have found the biggest problem with fan motors is their screw-on ground tab. The last time I had my fan motor out I soldered the ground tab on so there's no question about how well it grounds. About the only way the fan motor can draw too many amps would be the commutator rubbing against the field coils and I've never known of that happening. I have seen a few that were seized because their fan end bronze bushing had gotten packed with real fine dust which eventually caused them to seize.
 

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Discussion Starter · #12 ·
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Bumper Gas Automotive exterior Automotive wheel system Auto part
I have found the biggest problem with fan motors is their screw-on ground tab. The last time I had my fan motor out I soldered the ground tab on so there's no question about how well it grounds. About the only way the fan motor can draw too many amps would be the commutator rubbing against the field coils and I've never known of that happening. I have seen a few that were seized because their fan end bronze bushing had gotten packed with real fine dust which eventually caused them to seize.
Received new relay today. As it turns out it is not the same as the one currently in the car. The new one has 5 prongs, mine only has 4... Guess I should've looked closer.
I have found the biggest problem with fan motors is their screw-on ground tab. The last time I had my fan motor out I soldered the ground tab on so there's no question about how well it grounds. About the only way the fan motor can draw too many amps would be the commutator rubbing against the field coils and I've never known of that happening. I have seen a few that were seized because their fan end bronze bushing had gotten packed with real fine dust which eventually caused them to seize.
received new relay. Unfortunately it has one more connector than the one I hope to replace.
Guess I should have paid closer attention when ordering.
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Motor vehicle Automotive exterior Bumper Grille Automotive lighting Motor vehicle Automotive exterior Gas Bumper Auto part
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Motor vehicle Automotive exterior Bumper Grille Automotive lighting Motor vehicle Automotive exterior Gas Bumper Auto part Motor vehicle Automotive lighting Bumper Automotive tire Vehicle
 

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View attachment 35428 View attachment 35428
Received new relay today. As it turns out it is not the same as the one currently in the car. The new one has 5 prongs, mine only has 4... Guess I should've looked closer.

received new relay. Unfortunately it has one more connector than the one I hope to replace.
Guess I should have paid closer attention when ordering. View attachment 35425 View attachment 35425 View attachment 35426 View attachment 35425 View attachment 35426 View attachment 35427 View attachment 35425 View attachment 35426 View attachment 35427
I did that once so don't feel bad.
 
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