Is there a way to redo the blower motor wiring with a relay like you can the headlights? My wiring harness is partially melted, and I'd like to run it all with relays so I don't have so many amps running through the dash wiring. I'm just no sure how you could get the different speeds.

I guess I don't really need anything other than high, b/c there are so many holes that it can't even keep up on high, lol. I wonder if using a relay would actually make it blow harder?

 

I did a quick search, and found several blower motor relays for all sorts of vehicles, but no info on how they work. Do they make relays that have variable voltage or amperage inputs and outputs? If so I guess it would be a pretty simple task.

 

You bascially wire the relay to provide the switch with power on LOW and MID and then have HI on the switch trigger the relay to run the battery power straight to the blower.

Josh

 

So it's one relay with multiple outputs? And the output is determined by the input which is the output of the multi position switch?

 

Not quite, A 5 prong Bosch relay would have one output (87a) that is always hot, that would run to the original switch likely with a new wire.

Output 87 on the relay is the "switched" portion.

When HI is toggled on the switch a new wire would run to from that particular output to terminal 85 on the relay which would engage the relay to send full battery voltage to the heater. So the new HI output from 85 would tie into the old heater wire coming from the old low-mid resistor.

Josh

 

I couldn't sleep last night, so I was sipping a little crown to help me relax. Your post makes much more sense now.

So in what you described the relay is only sending power on high, right? Otherwise it goes through the switch as usual?

 

I looked at a few wiring diagrams, and several have a resistor pack and a relay. The power comes from the relay, and the switch provides the ground.

Here's one diagram that is pretty easy to read:



Would this be a better setup than what we have?

 

No, that diagram is showing the relay supplying voltage to the switch, the actual heater switch works exactly the same as our trucks.

I'm sure there are a few ways to do it. With my idea, the voltage runs thru it for off-low-mid and then is activated for HI. And with the relay staying in the engine compartment, likely right there next to the battery you only have a couple feet of wire to the blower, full voltage.

Rather than the voltage coming from the solenoid/ battery thru the harness, thru the fuse block, up to the switch, down thru the resistor and then up thru the harness again back to the blower motor. It sucks just typing all that, let alone expecting the voltage to go all that way when the blower is right there.

Same ordeal with the headlights BTW.

Josh