Is there a TECH article or any good threads on adding a relayed HOT wire and bigger/better ground to the blower-motor ??

I read somewhere that simply jumping a hot wire from the battery to the terminal at the blower would yield cyclone-like wind from the vents, sort of really kicking the blower into high-gear, thus proving that it suffers from voltage starvation.


Whatever slows it down for the lower speeds works off the ground, right ?? or is it the HOT ??

Thanks.

 

The resistor assembly mounted in the ductwork slows the blower motor. The speed selector switch controls which resistor is in the circuit for the speed selected. "High" speed on the selector bypasses the resistor and puts a full 12 volts to the blower.

Anything in the truck that you hook directly to the battery is going to run faster and be brighter than the original wiring can supply. That's just the way Ford designed it. They put the bare minimum size wire for everything inside the truck. If you ran a wire directly from the battery to the headlights, they would be brighter too.

It's a matter of how much you want to re-wire the truck.

 

So, I can find the high-speed wire down-stream of the speed-selector switch and use it to trigger a relay, which in turn provides full voltage directly at the blower, right ??

This is providing the speed selection resistors are in the positive wires, and not the ground.

Thanks.

 

If you jump the black and red/orange wires at the plug to the speed switch (called the fan relay), you'll get the full force 12 volts you're looking for. What's interesting is that it's much higher fan speed than you get with the switch set to high.

 

Meaning I could just route leads from those two wires through a toggle-switch and "jump" them at will, with the factory function being un-molested when the toggle was OFF, RIGHT ???


Or must those two wires be dis-connected from the switch before "jumping" ??


Thanks.

 

You would have to experiment with it. I've only done it with the wires removed when replacing the plug. But it did run for about a week like that. A double throw switch might work best where one throw maintains the factory routing.

 

I un-plugged the connection at the blower-motor and rigged a pair of short jumper-wires, such that I could test voltage at the blower without having to cut into the insulation on the wires.

With engine idling, max A/C on, and highest fan speed on, I only had 10.8-volts at the blower; no other electrical drains were in use.

Not surprising, considering that the current must travel through the firewall, ignition-switch, fuse-block, fan-switch, back through the firewall, and finally to the blower, then the ground must travel back through the firewall, through the resistor mess, through the speed-switch, and finally to ground; it's a wonder it works at all.

I have 14.2-volts at the main-power-junction/remote-voltage-sensing location, which is less than a foot from the blower.


I used two twenty-foot 12AWG test-leads, one on HOT and the other on GROUND, at my temporary jumper-wires, and was able to boost the voltage to 12.6 at the blower, and there was a very noticable improvement in blower speed; with more suitable length wires, I should be able to get close to the 14.2-volts.


I mounted two relays onto a bracket that mounts to the top two blower-screws, routing a 12AWG HOT through one, and a 12AWG GROUND through the other, splicing these wires into the proper wires at the blower plug.

A dry run without the engine running yielded a VERY noticable improvement in blower speed and the motor really smoothed out and ran much better.


Un-expected company popped in, so I was unable to finish the project and test voltage with the engine running; so, I will have to finish it up tomorrow and test voltage then.

Thus far, I am well pleased.

 

Keep us posted.

I live in Pennsylvania, and the winters get pretty cold here and anything that would help boost the output of the blower would be a "warm" welcome.

Speaking of blowers: has anyone seen the high output heater cores? I've seen one once at the junk yard and I was wondering what the difference is.

 

You may be meaning something different than what I am talking about; but, it is my understanding that ONLY the non-A/C cabs came equipped with a much larger "high output" heater-core and a much stronger blower-motor.

A smart man would figure it would have been the other way around; buy a fully dressed truck and receive an anemic blower and kiddie-size heater-core, or buy a bare-bones truck and get a DELUXE blower/heater package as standard equipment; it don't make good sense.

 

Not true. I have a non-a/c truck and it has the smaller heater core.

I've saw a truck in the yard with dual battery trays and heater box that had "high output" molded into the case.......

It was not a diesel truck either. Maybe a cold weather package. They crushed the truck before I had a chance to go back for the assembly.

 

I got things back together and now have the rest of the numbers.

Before any modifications, engine running, A/C on max, fan-speed on highest setting, no other electrical drains, I had 10.8-volts at the blower-motor and 14.2 at the main power junction.


Now, with both a 12AWG relay-switched direct HOT and GROUND, both spliced into the existing blower-motor wires near the disconnect-plug, and the factory system otherwise intact, with the relays OFF, I still have 10.8-volts; but, when I flip the switch that energizes the relays, thus giving the motor all available power and ground, I have 13.5-volts at the blower and still 14.2 at the main junction.


Blower speed probably doubles, the anemic rattling hum disappears, and the blower runs smooth as silk.


This will have to be good for all components in the system, taking a load off of the ignition-switch, the fuse-block, the fan-switch, and wiring.


The difference at the vents is definitely noticable.

 

Can you post a wire diagram of what you've done?

 

I ain't smart enough to do a diagram; but, I can tell you what I did.


I made a simple folded aluminum bracket that is held to the blower-motor flange by the two top-most screws.

This bracket is approximately 8" long and I drilled seven equally spaced holes for future relay installations; I only used two holes for this project.


Just above the blower is a good copper GROUND-strap that grounds the hood to the firewall.

I used the firewall end of that strap for an attachment point for my 12AWG GROUND-wire.

I spliced both little black GROUND-wires from relay-terminal #85 into the 12AWG GROUND-wire, thus providing GROUND for the switch-circuit of both relays.

This GROUND-wire attaches to relay-terminal #30, or "battery", of the GROUND relay.

Another length of 12AWG wire attaches to relay-terminal #87 and from there it splices into the existing GROUND-wire near the blower-motor plug.

The relay-terminal #86 "switch" wires of both relays are spliced into one wire that runs through the firewall, into the cab, to a switch mounted in the dash.

For HOT, I started with a 12AWG wire connected to the HOT stud of the starter-relay, which is also the main power junction.

This wire goes to relay-terminal #30.

Then, from relay-terminal #87, a 12AWG wire splices into the existing HOT wire at the blower-motor plug.


Turning the fan-speed switch to HIGH, then flipping the dash-mounted switch to ON, thus energizing the relays, switches direct full voltage to the blower-motor.

The single dash-mounted switch controls both relays.

 

If this was my truck, I would pull the blower motor, replace it with a new one, and while I was in there, I would clean the blower fan of ALL dirt and stuff. Also, clean out the area inside the heater box. They're always attracting leaves, etc.

I doubt that the OEM heater motor will survive for very long running at these new voltages. Its around 25 years old!!!

 

Before attacking this project, I removed the cowl, kick-panels, blower-motor, and A/C air-box.

I dug out two five-gallon bucket-fulls of leaves, pine-needles, dead mice, black rotten gook, etc.

I washed and flushed the A/C air-box and used some foaming cleaner on the evaporator itself.

I attached screen-wire underneath the cowl openings.

I installed a new heater-core and cleaned another bunch of yuk out of there.



When it comes down to blower replacement, I am gonna research and find out just what year-model Crown Victoria blowers will interchange.

Does anyone know which years the Crown Vic blowers are a bolt-in fit ??

From what I hear, they are supposed to blow like a tornado.