BLOWER MOTOR RELAY MOD

[MIDNIGHT RIDER]

Sometime back, I read where someone routed the wiring of the blower-motor through a relay, thus making the fan blow like a cyclone, instead of like an asthmatic on a dusty day.

They didn't expand on exactly what they did, just stated that it was done and did work well.

Whoever has done this, please share detailed instructions on exactly which wire the relay was spliced into.

I don't really understand what happens in the motor when speeds are selected/changed.

If I simply cut into the main blower-motor wire, under the hood, and spliced in a relay, giving the motor full voltage, and the wimpy dash mount switch only triggering the circuit, will that accomplish what I want to do??

Do I assume correctly that the full current to the blower is routed through the dash mount switch??

Thanks.

 

[Agnem]

The motor already has full voltage. It is the swtich that varies the amount of ground that it sees. The switch selects one of several resistors that go in series with the blower motor. This assuming your year is the same as an 87'. A "relay mod" would probably consist of just a relay between the orange/black wire and ground. However, according to the schematic, full speed should not have a resistor in the circuit, consequently a relay mod may only compensate for resistance in the switch due to age.

 

[adrianspeeder]

Workin' on this right now actually in the 88 as I started to smell that wonderful electrical burnin' of ozone.

Before I owned it, apparently the fuse for the blower and AC clutch melted.

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This also took out the turn signal feed so some ****** with tools did this to bypass it above the fuse panel.

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Now here is why we don't use those stupid crimp connectors on yer trucks.

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At least they had the thought to downgrade the fuse to 20 from 30, but you can see how corrosion from the crimp connectors built heat and started to melt stuff.

Now the fix, I have enough capacity in my aux fuse panel for the headlight relay rewire and aux reverse lights. Power comes directly from the panel through only a 15 amp fuse (ten blew), and right into the hot side of the motor.

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I abandoned the melted fuse position 9 by cutting the blower motor feed off and goin straight to the motor from where my aux fuse panel is.

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Kinda funky how the dash toggle actually switches the ground side of the motor. Depending on which of the three resistors is grounded determines the fan speed. So basically you would need a relay for each speed if'n you wanted to go that route.

Now two things. Gotta try to figure out what caused the first sequence of failure and figure out how to get power correctly to the AC clutch system. Tear into the dash this weekend hopefully.

Did also get my aux panel wiring cleaned up with everything labeled, soldered, and heatshrunk.

Adrianspeeder

 

[swampdigger]

Damn speeder, I dig that aux panel you got going there....

 

[TLBREWER]

Speeder

Maybe you should do an electrical clinic at the next IDI Rally. Seems like you always pick the most obscure electrical problems we've all thought about and tackle it.

Tom

 

[MIDNIGHT RIDER]

BRING ON THE PICTURES--MR. SPEEDER

Now here is why we don't use those stupid crimp connectors on yer trucks.

I believe that there are different conductive capabilities of CRIMP-CONNECTORS of various qualities, some being of a poor conductor, therefore creating resistance and building heat.

I have had the same experiences with blade-type fuses; some will never shoot, regardless of load; they just overheat and melt everything close to them.

I only use BUSS fuses.

Where I can, I solder/heat-shrink; but, I will admit, I have several connections that use crimp-connectors.

I haven't had one melt like the one in your picture, in all my driving life; but, obviously it does happen, as per the photographic evidence.

How would you address that particular connection?? solder/heat-shrink, or some other method??

Kinda funky how the dash toggle actually switches the ground side of the motor. Depending on which of the three resistors is grounded determines the fan speed.
Adrianspeeder

Let's say I turn the key on, with the blower switch OFF, and then jumper a wire from the blower housing to ground, will the blower come to life??

I was trouble-shooting the wipers, on my old 78 Chevy K-20, replaced the switch--no go; then, while poking a hot jumper to various points on the wiper-motor, I discovered that the dash-switch switches the ground, a very perplexing situation.

To this day, after several hundreds of thousands of miles, there is a grounded toggle in the dash that will turn on the wipers;--WEIRD--huh??

 

[adrianspeeder]

Speeder

Maybe you should do an electrical clinic at the next IDI Rally. Seems like you always pick the most obscure electrical problems we've all thought about and tackle it.

Tom

Heh heh, thanky. You do know I'm a third year electrical engamaneerin' major right This is the stuff I'll be doin' fer the rest of my days.

Damn speeder, I dig that aux panel you got going there....

Thanky, here's a better view.

1. CB radio
2. Auxiliary reverse light power
3. Air Horn compressor power
4. Air Horn relay
5. HVAC blower (stock wiring melted for some yet unknown reason)
6. 12v power point's in the dash
7. Low beam power
9. High beam power

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Let's say I turn the key on, with the blower switch OFF, and then jumper a wire from the blower housing to ground, will the blower come to life??

Not the housing...

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If you would cut the orange with black tracer wire coming out of the motor and sent it to ground, with the key on it would come on full, but this is just what the dash switch does on high.

My problems are on the unswitched hot side of the motor (I think) so I ran a direct hot wire from my fuse panel to the brown with orange tracer on the hot side of the motor.


Edit: While I'm up on my breaker box, (instead of soap box... get it? ) these "suitcase" connectors are not good either.

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You can kinda see how when exposed to air the copper wires and aluminum tab corroded and this connection started to heat up melting the insulation.

Now don't misunderstand, crimp and suitcase connectors are handy to have for emergency repairs, but I frown upon them for permanent wiring. This is what I had to do in a dorm parkin' lot when I was goin' to school down in philly to make the air horns work. Not too bad fer 15mins of work in the rain.

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Adrianspeeder

 

[Exekiel69]

Adrianspeeder, where can I get one of those eux fuse panels? I'd like to get Myself one before I start burning things.

Thank You.

 

[MIDNIGHT RIDER]

LET THE SPARKS FLY !!!

Edit: While I'm up on my breaker box, (instead of soap box... get it? ) these "suitcase" connectors are not good either.

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Adrianspeeder

It's amazing how many people, that I would think should know better, have a reverent awe for those wire-cutting splice-lock connectors.

High-dollar name-brand gooseneck trailers will have them by the hand-fulls; and, after a few trips, you have to yank a wire to get a whole string of lights to come on.

I keep a few for dire emergencies, but never use them.

 

[MIDNIGHT RIDER]

UNDER THE HOOD FUSE BOXES

Adrianspeeder, where can I get one of those eux fuse panels? I'd like to get Myself one before I start burning things.

Thank You.

My intentions are to rob one of those neat fuse boxes from under the hood of a later model truck, one that has maxi-fuses, standard fuses, and several relays.

Then, wire by wire, I am going to completely eliminate the mess under the dash.

It is much easier standing in the rain, in the dark, replacing a fuse in a box under the hood, than it is to lay on your back, in a dirty floor, all contorted up, trying to hold a flash-light in one hand, needle-nose pliers in the other hand, and your legs sticking out in front of oncoming traffic.

 

[Agnem]

You'll find those auxiliary fuse panels at NAPA. I've started using them on everything.

 

[Mr_Roboto]

I'm with Mel, a relay will only fix blower problems if there is a problem with the wiring or switch. If the switch has high resistance, just replace the switch.

Crimp connectors are fine, if you use the proper crimping tool and of course a good connector. I used to be a machine builder and our crimpers had to be sent out and "calibrated" every 6 months to keep ISO certification to the machines. These were ratcheting type crimpers which would not release without the crimp being completed to the proper depth.

Simply squeezing a crimp connector with pliars will certainly NOT give a good connection.

 

[h2odrx]

i had a melt down in my fuse box too.. i went and got one from a 90's model ranger at my friends yard, then one by one switched all wires out and replaced. it took me a little while but it looks and works good. my next project will be the under hood wiring.

 

[adrianspeeder]

High-dollar name-brand gooseneck trailers will have them by the hand-fulls; and, after a few trips, you have to yank a wire to get a whole string of lights to come on.

I'd be Pissed if I found that for what I see them gooses go for pricewise....

ANyway,

Pulled the HVAC panel today and looked for trouble.

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Did find out there is a lightbulb that was burnt out back there though.

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Didn't find anything fried electrical wise which makes me worried to what caused the original fault on the blower/clutch circuit. Plan at this point is to keep the blower motor on the new 15 amp circuit with a "key on" controlled relay to buypass the stock power wire. The hot wired direct with a fuse method right now has a problem of even with the key off the blower motor still runs.

Using the Fluke meter, sending power directly to the AC button, I found the initial spike was 1.2amps with a steady draw of .2amps. What I'm gonna do is run a new line from the to be added blower relay directly to the AC switch with a 5 amp fuse.



Interesting comment from where I'm also posting this on fullsizebronco...

Computer will shut off the A/C at WOT.

No way for that to happen though, it's just 12v sent to the computer when the AC is manually turned on and the pressure switch locks the AC clutch. No way for the computer to feed back and control anything. Yer prolly right on it bumping the idle.

Sometimes I wish we had a retired powertrain engineer from ford we could poke questions like that too.

Adrianspeeder

 

[adrianspeeder]

Well back to runnin in the cool today. Got a 15amp circuit drivin a new relay that is triggered when the PCM relay comes on. The relay then powers the blower direct and backfeeds to the stock AC button with a 5amp fuse for the most protection I can give it.

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Adrianspeeder