Temporarily converting HVAC fan speed from 3 spd to single spd. X-posted

[bullnose1985]

Hello All,
Experiencing HVAC havoc in ol'blue. However the leafs have fallen and that means it's wood cutting time. Ol'blues call to Duty.

So of course the heater goes out.....

background:
power to the fuse and fuse not burnt out.
No power at switch, no power to fan or resistor.

just wanted to run my idea past the FTE brain trust befour I proceed with my plan prior to executing it in order to possibly keep me from burning up the truck or making things worse.

If i understand the wiring diagrams on Gary's site. For the hvac fan speed control. Power goes from the fuse block to the fan and the switch controls the ground side of the circuit. Feel free to correct me if I am wrong.

so temporarily I plan to to run a fused relay from the battery directly to the blower fan. Then run a simple wire or two thru the firewall to under the dash mounted switch.

thus providing a single switch for high fan speed operation only.

figure since on high the fan bypasses the resistors all together so it Would work?

what do you good people think?

[Gary Lewis]

Jon - I think you copied your FTE post and pasted it here.  

For simplicities sake I've pasted the schematic here.  And if you have power at the fuse but not the switch then you have a problem with the wire between.  So I wouldn't start adding relays and wires.  I'd find out what is wrong on that fairly short wire, which leaves the fuse block as a brown/orange wire and then changes to brown/white at C606, which is supposed to be at the left side of the switch.

[bullnose1985]

Hi Gary,
I did cut copy and paste the same message kind of fishing for a answer. As I am sure your aware in Missouri the weather can be different from hour to hour. The ground should be dry enough to get to a heavily wooded area down by the creek to harvest some prime hard wood for next winter.

I have a buddy that took off to help. So time is of the essence. I know in the past I can part there and the heat from the engine vs the very cold water alway causes the windows to fog over. Come up out of the of that area is Harry enough without fogged over windows. Very narrow very washed out and extremely steep.

Yes i have that and the rest of the HVAC chapter on my tablet. Very very helpfull


.

I didn't mention that the resistor is in bad shape as well.

I understand that  it's a short wire but  it appears to be behind and under the dash. I am out of daylight for the day and tomorrow morning it's go time. This would be very temporary like to be corrected by end of day tomorrow Thursday morning at the lastest..

I was just curious if it would work the way I was thinking.

By the way I was reading a few threads regarding Big Blue those threads are pure gold. Thanks for all you do for everyone around here. You may not hear it every day but your efforts are much appreciated .

[Gary Lewis]

So your weather varies from hour to hour?  In Okiehoma we say if you don't like the weather wait 15 minutes!  

On the heater, I think what you proposed will work - if your resistor pack is good.  The resistors ground the motor, so if they aren't good it still won't run.  But High has full ground, so that should work regardless.

[1986F150Six]

Jon, this is likely a dumb question as I think "outside the box"... did this condition just suddenly appear? What about your gauges and turn signals? I ask because if the ignition switch gets sticky in cold weather, it can "rest" in such a position as to affect all of these things.

[mat in tn]

this is a very good point. my truck has this issue. its part of its personality at this time. when it turns cold like 'now' the ignition switch (key) does not fully relax back into the run position. i have become trained to return it myself and barely even know im doing it.
yes it is the grease inside the actual switch that hardens up over time and creates enough drag to hold against the return spring. funny thing is by the time i get home i have forgotten all about it

[mat in tn]

oh and i found it doing this because the heat did not work nor did the radio. wiggle the key and all good.
now where did i put the bag of ignition switches?

[bullnose1985]

Hi Gary,
I had pulled the switch, blower and resistor. The switch is in working order checked it with my meter. The blower was stiff to say the least but works. Almost jumped out of my hand when I touched it to the battery. The resistor was heavley corroded I cleaned up the terrmerals and tried to test the resistor it's self and didn't get any ohms at all out of it also checked it with the continuity and it didn't make a circuit. So I will assume it is shot.

Hence I figured I could run it at high and bypass the the resistor all together. Honestly I don't ever run the fan unless it's on high anyway.

Thank  for  your time and effort.

[bullnose1985]

Hi 1986F150Six,
Yes everything works as it should. It's only a heater no air in ol'blue. No sticking that I am aware of. I use a key chain that allows me to unclaspt the ingniton key so not to jackhammer the ingniton switch with a heavy key chain full of keys.
The problem seems to be between the fuse block and the blower.

Thanks for your time and effort.

[bullnose1985]

Hi Mat in th,

No everything is good with the key switch. I replaced it a few years ago. The original someone has shot the inside with lithium grease which just collected dust like a magnet and had ran a heavy set of keys.

Thanks for your time and effort .

[bullnose1985]

Thank you mat in tn.

[bullnose1985]

Update my friends.
I ended up using a converter and a heat gun. Lol. It worked.
Thank you all for your help it is greatly appreciated

[Gary Lewis]

Converter = inverter?  Meaning 12v dc to 120v ac?  That should do it!

On the resistor pack, there is a thermal limiter in the line and when it blows it appears like the resistors are bad.  The limiter looks a bit like a diode, so check your resistors ahead of it.

[bullnose1985]

Hi Gary,

Yes inverter rather my apologies.

As that say a pictures are worth a thousand words.these pictures where taken after cleaning. I am getting tired and going to have to hit the hay. I will talk to you guys tomorrow.
Thanks for everything Gary.

[RenoHuskerDu]

I have a tip related to that resistor. Puddles the 86 suffered a burnt one a few years back, due to leaves and tree detritus accumulated in there. Smelled like a campfire in the cab one morning.

I kept back burnering an idea I had to put a screen across the slots of the cowl. Never got to it, but I would tape off the cowl if parking under oak trees in fall.

Then we bought Farm Truck, our first Bricky. I spied its improved cowl. It fits a Bully, and keeps out leaves much better.  But the secret is out, as many Bricknoses in junkyards have a missing cowl. We've switched to a buy-entire-parts-trucks approach, because we are fortunate to live rural and have acres. At this point we have enough cowls to equip all our Bully trucks with a Bricky cowl. No more burnt resistors.

FYI

[Gary Lewis]

Big Blue is sporting one of the pin cushion cowls.  Works great.  

[mat in tn]

pay attention on the resistor. it has multiple resistors to create three different speeds, but it also has a thermo-fuse crimped in there too. you cannot see if is blown it must be checked for continuity on its own . either way it requires a replacement unless you are willing to replace it. fiddly and needs to be crimped and not soldered but still doable .

[bullnose1985]

Hi Reno,
I was kind of surprised I only found one pine neddle in the blower fan compartment and nothing but a shot resistor asy in the other opening.
I will probably convert it to a single speed via a relay. I like to keep things as simple as possible when possible. This is one of those times.
I may have to look for a pin hole intake cover.
Thank you for you're post.

[bullnose1985]

I will have to put that on my next junkyard shopping list. Good advice.

[bullnose1985]

Hi mat in tn,
Oh yeah its shot, ohm and continuity zero it is toast. I cleaned and re smashed the crimps nothing worked. I am going to turn it in to a single speed fan tomorrow.
Thanks for you're post.