The Impossible Blower Switch Problem Challenge !
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Joined: Jul 2012
Posts: 51
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From: Columbus Ohio
The Impossible Blower Switch Problem Challenge !
So last year the blower switch in my 1980 stopped working. I replaced the blower motor . . . nothing. I tested the switch . . . switch is good. Fuses . . . ? Fuses okay. Wiring? looks fine. Can anyone please tell me how, from beginning to end, to start to trace and find what is causing this problem? Eternal thanks.
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still can be the relay,
relay is off power flows from relay to resistors to motor,
relay is on power flows from relay to motor direct
relay is off power flows from relay to resistors to motor,
relay is on power flows from relay to motor direct
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
It also can still be the switch. Checking continuity on a switch will not [necessarily] indicate a fault-free switch. If the contacts are burned and carbon covered, they can still show continuity (with relatively low resistance); but they might not be able to transfer adequate current to run the blower. That switch can be opened to clean the contacts, then put back together if undamaged and still serviceable.
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Melting Slicks
Joined: May 2015
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From: Cape Girardeau Missouri
Does the blower run at low speed whenever the ignition switch is at "RUN"? It should. Put the key at "RUN" without starting and you should hear the blower run. The LOW speed setting on the fan switch has no function due to an electrical bypass around the switch to provide "constant ventilation" as the feature was called.
If it does not run constantly at low speed then given what you've already done (did you test the old blower motor before going to the extreme amount of work to replace?) I would first suspect the high-speed blower relay. It's on the firewall on the passenger side and has five wires in the connector. Three are heavy 12 gauge and are red, dark blue and purple. DISCONNECT the negative battery connection and the connector at the relay. Using a test light check between the relay connections made by the dark blue and purple wires. No or dim test light? Clean the connections thoroughly and test again. Still no or dim test light? Replace the relay.
If the fan does run constantly write back with that info and I'll give more troubleshooting information.
If it does not run constantly at low speed then given what you've already done (did you test the old blower motor before going to the extreme amount of work to replace?) I would first suspect the high-speed blower relay. It's on the firewall on the passenger side and has five wires in the connector. Three are heavy 12 gauge and are red, dark blue and purple. DISCONNECT the negative battery connection and the connector at the relay. Using a test light check between the relay connections made by the dark blue and purple wires. No or dim test light? Clean the connections thoroughly and test again. Still no or dim test light? Replace the relay.
If the fan does run constantly write back with that info and I'll give more troubleshooting information.
