Help with wiring to blower

by Iguy Sat Nov 24, 2018 8:18 pm

Sorry if this has been answered already, I couldn't find it.

Looking at the wires that run to the blower, what is the canister mounted to the firewall up top, a capacitor or something? It looks like I could bypass it, not sure if that's possible.

What is the rectangle thing with the coiled wires inside the blower housing for?

Also, I have an un-used connector with the yellow striped black wire, what is this for?

I'm looking to clean up anything I don't need. Thanks!

Hopefully the picture shows up for reference.

by Mcarlo77 Sun Nov 25, 2018 12:51 pm

If your intent is to get rid of the blower motor (not sure why you'd want to do that?), then yes, you can remove the resistor (rectangle thing with coils) and round capacitor. The resistor enables the various fan speeds. The capacitor, I believe, helps to energize the blower motor. Have no idea what the plug with double yellow w/blk stripe wires are for. My Laguna with A/C doesn't have those.

by Joe73 Sun Nov 25, 2018 1:08 pm

My 73 is a non a/c car. I dont have that capacitor thing like you do. I do have the 2 yellow wires with black stripe though. It comes out of the same harness as your blower resistor does and it goes to a "thingie" just to the right of the blower housing. I cant remember what the part is called but its held onto the firewall with 2 screws, silver in color and the plug inserts from the bottom upwards. Its located just to the right of you pic, between the blower housing and the 2 heater hose connections. If your standing in front of your car, facing the firewall, the thingie is at 10 oclock to the heater hose connections. And to the left of that is your heater housing. I'd have to dig through my stuff to find out what that thing is but my car has it and my M&H harness came with the plug and yellow/black wires as well.

by Iguy Sun Nov 25, 2018 4:55 pm

Thanks for the replies. Mine is a non AC car. I'll keep the blower, that makes sense the coils are for different fan speeds. I was just trying to get rid of any wiring I don't need, I could just tuck the yellow wire and connector in some loom.

by fasrnur Mon Nov 26, 2018 1:10 am

I believe the plug with the two wires goes to the back of the block and is an oil sender connection.

by clanceman427 Mon Nov 26, 2018 7:29 am

The plug with the 2 wires goes to the back of the passenger side cylinder head to a non coolant temperature sensor. This turns your blower fan on low once engine reaches a certain temperature

by Mcarlo77 Mon Nov 26, 2018 10:58 am

I thought the blower fan was strictly manually controlled via the fan switch? What purpose would be served by having the blower fan speed be dictated by engine temp?

I've got two yellow wires like these (no stripes, though) only each wire has it's own plug. They definitely go to a switch down low on the passenger side of the block. I, too, assumed they were for the oil sender.

by Joe73 Mon Nov 26, 2018 11:37 am

Ok, I got a chance to take a look at my car and the 73 service manual. Kevin is correct!!! Those (2) wires, which are actually black with 2 yellow stripes each, goes to the coolant temp sensor on the rear of the passenger cylinder head. Nice catch Kevin.

The silver thingie I was referring to is a delay relay and it has a blue and tan wire going to it and the same exact plug as the black yellow wires discussed above.

In pic #1 below I show how I had it plugged in but I then switched out the plug and put the correct blue/tan wires into the delay relay pic #3.

Also pic #2 is of the underhood wiring diagram for the blower area for those who need it.

by Mcarlo77 Mon Nov 26, 2018 12:21 pm

So, what function does that thermo switch serve that can't be accomplished by manually adjusting the fan speed via the dash switch? Unless, it has something to do with the cross-ventilation air flow to provide more fresh air to the cabin to lessen the chance of passengers choking on rich exhaust fumes at startup? I just don't get it...seems redundant and completely unnecessary to me.

Also, where exactly is the Oil Sender, then?

by Joe73 Mon Nov 26, 2018 12:32 pm

Oil sender is directly next to the distributor on small blocks.

by clanceman427 Mon Nov 26, 2018 6:37 pm

I guess in 1973 model year Chevrolet decided that the fan must always be on at least low speed once the engine hit the set mark. I seem to remember it being 90 degrees engine temp to close the circuit. I saw it in my owners manual, I’d upload a photo but unfortunately my car is covered up at the moment/can’t get to it.

by Mcarlo77 Mon Nov 26, 2018 7:01 pm

I seem to remember reading something about GM being concerned with possible inhalation of exhaust fumes inside the cabin with no means of allowing fresh air inside once they did away with wing vents on cars. So, cross-ventilation was their solution by having a continually running blower fan at low speed. Just seems weird they would go to the trouble of adding a circuit that would regulate that depending on engine heat.

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