Protecting your blower motor switch (non-EATC)

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Protecting your blower motor switch (non-EATC)

August 10, 2012, 10:44:01 PM

Here's a little tip for those of us without EATC: we all know that the connector to the fan switch is pr0ne to melting. Ford actually redesigned it a few years later to run the current through a relay when the fan is switched to Hi. A few years ago I rewired it using my 1997 Explorer EVTM as a guide, and hopefully the connector won't ever melt again. It's a pretty easy project for anyone who is interested.

Protecting your blower motor switch (non-EATC)

Reply #1 – August 10, 2012, 11:29:46 PM

Do you have details to share? This sounds like a worthwhile project to undertake, especially if you are already in the dash doing something like replacing a heater core or something else of that nature.

Protecting your blower motor switch (non-EATC)

Reply #2 – August 11, 2012, 12:11:43 AM

yeah, ill put it up on my photo bucket link with your credits within the evtm bundle.

Protecting your blower motor switch (non-EATC)

Reply #3 – August 11, 2012, 12:14:03 AM

Well, I don't have a scanner, but I do have a digital camera:

The diagram doesn't specify what kind of relay, but I used a 50A one just in case. Explorers use two sizes of relays, big square ones and ones that are half that size. This is the larger kind. They come in different amp ratings, so be careful which one you use. I also used a relay block from a 1995-ish Taurus for mounting the relay, but that might have been more trouble than it was worth since I had to replace all the wires with heavier-gauge ones. I went that route to avoid any chance of short-circuits between relay terminals. There are aftermarket mounting blocks for single relays which is what I would use if I had to do it again.

Protecting your blower motor switch (non-EATC)

Reply #4 – August 11, 2012, 01:02:07 AM

Awesome, Thank you!

Protecting your blower motor switch (non-EATC)

Reply #5 – August 12, 2012, 11:39:17 AM

This should do fine, not sure if this is what you ended up with or not but i cant see over complicating it.
Notice the R&R of the original fuse to 5A (approx).

You can intercept the existing DB/LG wire for the relay then apply ground & power as shown.

Protecting your blower motor switch (non-EATC)

Reply #6 – August 12, 2012, 12:04:58 PM

Thanks jcassity, that is terrific!

Protecting your blower motor switch (non-EATC)

Reply #7 – August 12, 2012, 12:19:24 PM

let it cyclel through here a couple days, several eyes on things are better than one set.
Im now working on headlamp relays while jacking with this amp guage converting it by using a volt meter. digikey has a few.

Protecting your blower motor switch (non-EATC)

Reply #8 – August 12, 2012, 03:51:52 PM

I don't see how that protects the blower motor switch...it protects the multifunction switch (which is a mod I hadn't considered), but it still routes all the current through the blower motor switch when set to Hi.

Apologies if I hadn't been clear about which switch I was protecting. It looks like we have two good mods here.

Protecting your blower motor switch (non-EATC)

Reply #9 – August 12, 2012, 04:02:46 PM

ok, you missed calling out which one you were protecting. Will fix now.

Protecting your blower motor switch (non-EATC)

Reply #10 – August 12, 2012, 04:09:57 PM

I think your mod is also valid, maybe they should be combined?

Protecting your blower motor switch (non-EATC)

Reply #11 – August 12, 2012, 05:50:45 PM

Quote from: Quietleaf;395817

I think your mod is also valid, maybe they should be combined?

Agreed. Jcassity's mod protects the function contol switch, which isn't a bad thing, as it is the hot side to the blower. Quietleaf wants to protect the blower speed switch, which we know melts the connector because that black-out "hi-speed" is carrying the full current load on the ground side, which would require that dual-relay gimmick to switch the ground, correct?

Protecting your blower motor switch (non-EATC)

Reply #12 – August 12, 2012, 06:22:00 PM

i just about broke my head trying to figure this out without as you called it a dual slave of a slave relay.

I think i nailed it,,, circuit is de-energized now on paper.
Add power to the upstream relay and power is also applied to the lower downstream relay coil and common contact after the motor.

**when high speed is selected the lower relay coil gets an open ground but the power for the motor is now able to see ground from the contacts.

this just might fly,, any thoughts?

Protecting your blower motor switch (non-EATC)

Reply #13 – August 12, 2012, 07:26:01 PM

Hmm. That doesn't look quite right. I believe this is what I had to do:

Edit: scratch that. Mine isn't right either...

Protecting your blower motor switch (non-EATC)

Reply #14 – August 12, 2012, 08:36:00 PM

Got it. Now I remember: I had to put the relay after the Hi output: