heater blower motor relay

Asked by Dec 25, 2013 at 08:10 PM about the 1967 Oldsmobile Cutlass Supreme

Question type: Maintenance & Repair

Installed new wiring on 67 cutlass with AC. I failed to save the Blower Motor Relay on the
heater blower motor. i can purchase a new relay but i cannot see what wires i have to add
and what they connect to. I looked on the wiring diagram but cannot see how the Blower
Motor Relay is wired. Looks like i have 2 wire leads on the relay. Thinking that the single
wire on the blower Motor Resister goes through the relay first. Anyone have any
experience with this?
Thank you in advance for your help.

4 Answers

21,385

understand how a relay works- a switch on your dash activates a switch in the relay connecting a higher voltage connection than you would want going through that switch on your dash- dash switch will throw the relay on- high voltage wires from battery to blower motor will be on either side of the relay- sounds like you may need a relay with more connectors

I did find the correct relay, has 4 terminals. I will have to work with the wires to connect properly. if i understand you correctly, from the battery, 13V, through the relay to the blower switch on the dash, 11V or so from the relay, the blower switch when in low, goes through the blower resistor then to the blower, say 5v, medium through the resister about 8v, then on high about 11V to the blower motor with minimum resistance. so the relay only regulates the voltage going to the switch on the dash????????

21,385

kinda, but not really- the switch on the dash has less power going through it- it has it's own connection to power- so the dash does not have any big, thick wires going to its switches- all that dash switch does is activate the connection in that relay, completing the connection there between 2 more powerful wires that then sends power to whatever big, hungry component needs activating- this saves on lengths of big hot wires and keeps a lot of potentially problematic power away from the driver's fingers- maybe some other guru can explain this simpler than me?

I had a heater blower problem with my 1967 cutlass. The blower would not always come on when activated at the dash. I discovered several problems. The circuit diagram in the shop manual as not correct. It showed two wire resistors to control blower speed whereas my car has three resistors yielding 4 possible blower speeds. The highest speed is obtained by sending 12 volts from the battery to the blower motor without any of the resistors. That's where the blower relay comes in. It does that. When the highest speed is requested the selector switch goes to the input of the relay and when the relay operates full unlimited battery is sent to the blower. If you cannot find your old relay, Radio Shack sells a 30 amp automotive 12 volt relay. This should be enough info if you have any electrical background. By the way, the blower motor wire is purple.

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