Relay Your Blower Motor

[86VickyLX]

When I did the fusebox in Vicky, I also decided to relay the blower motor. Why you ask? Because it was such a draw on the ignition switch, the switch was getting hot. I recently replaced the switch again, with no change in what it did. Now my EVTM lied to me. The wire colors that were shown in the EVTM were not what it was on the car. However, this wiring diagram is correct. First I'll have the original, and then my relayed one.
The end result is a faster blower motor on all speeds, and lower current draw on the interior's electrical system.

[87gtVIC]

Does it matter that pin 87a is doing the job that pin 30 normally does?

[86VickyLX]

Does it matter that pin 87a is doing the job that pin 30 normally does?

No. As long as the motor is off when the key is off or the heater controls is in the off position, it matters not.

[1987cp]

This sounds like a smart idea!

Also makes me wonder how I came to the conclusion a few years ago that the blower motor switch switched the negative side instead of the positive side, even though (IIRC) I've since verified that not to be the case. Go figure.

[86VickyLX]

This sounds like a smart idea!

Also makes me wonder how I came to the conclusion a few years ago that the blower motor switch switched the negative side instead of the positive side, even though (IIRC) I've since verified that not to be the case. Go figure.

It does switch through the ground side. Well speedwise that is.

[1987cp]

Maybe that's why I was confused. Too bad it looks pretty complicated to avoid having the fan load go through the speed switch itself.

What does the diagram mean by blower resistor "with thermal limiter"? Was that a fancy feature on later models?

[86VickyLX]

Maybe that's why I was confused. Too bad it looks pretty complicated to avoid having the fan load go through the speed switch itself.

What does the diagram mean by blower resistor "with thermal limiter"? Was that a fancy feature on later models?

If it gets too hot it won't work. It's basically a fuse in the blower motor resistor.

[gadget73]

Think circuit breaker. Thats all the thermal overload is. Its a self-resetting type like that metal one in the fuse box that runs the power windows.

The load does actually run through the switch. It just selects various voltage taps from the resistor to give your speed selection.

[1987cp]

A breaker in the resistor block? Why not? Must be what that weird extra wire is for on the later models?

[85crownHPP]

Good stuff!!

I got to poke around in all the blower stuff the other day in a Tempo, looks like its the same wiring setup. I was surprised at the fan switch being a ground selector too.
The problem with the tempo was the control head was burned out (fan speed switch, resistor and blower were all fine). The plug in the back of the old head looked like a burned up headlight switch connector

[L1011tristar17]

I'm thinking of doing this for my car since the blower motor died on me and the new motor needs a connector that has beefier wiring. Do you have any pics of what the setup looks like? Should I look for a specific relay at the parts store?

As a follow up: will this also work for a car with ATC? The electrical diagram I have looks a little bit different than yours.

[sly]

Here's the hack job I did on my 88. Power for the coil comes from the + line originally going to the blower and then the coil is grounded nearby (thin red wire - only had red 18gauge hookup wire at the time). Battery power comes to the common pin (30) on the relay (black wire here... only had black in 12gauge wire at the time) and then the normally open (87) pin goes to the + line on the blower. I did all this from the harness side of the wiring to the blower (just in case of future replacements) and it was a good thing too since my blower fried after about 2 years and I had to replace it. It was the original blower though... so it was probably time.

The magenta? wires are the two power wires for my amplifier that drives the 2 10s in the trunk.

[L1011tristar17]

That doesn't look as complicated as I thought it would be. What is the second red wire connected to? (The one that goes under the blower motor connector)

[sly]

That doesn't look as complicated as I thought it would be. What is the second red wire connected to? (The one that goes under the blower motor connector)

that's the one from the original + wire to the blower (doesn't need to be fat since it's just driving the coil)

[L1011tristar17]

Now I'm really confused. By the + Wire, do you mean the wire from the battery, or the one to the blower motor? To me, the red wire looks like it goes to the ATC Selector Switch (from Pin 85 on 86Vicky's diagram)