I have a 68 that I cannot get the blower to work (NO HEATER) and it's getting cold.
My diagram does not show the blower switch or blower as if this was an option on this truck.
I can put a hot on the blower and it works fine but not when I hook up the switch....SOMEONE HELP MAKE MY TEETH STOP CHATTERING PLEASE by sending me a diagram if possible.

Wayne S.

 

The blower switch should be on the right side of the heater control plate. Checked the fuse? If you have power to the switch, and still no go, sounds like a bad switch. As a second test, you could ohm the switch and see if it's good or not. If it's open on all settings, it's bad. But I'd be betting it's more likely power is not making it to the switch. MK

 

I have power to the switch but when I plug the wires back in the power goes away...this is nuts.

 

Looks like a corroded wire, switch or connection......seen it before you can measure the voltage with a meter but as soon as you try and use the power all the voltage is dropped at the corrosion.
Maybe try bypassing the switch it could be dirty/corroded/pitted/worn out.

 

My slide switch was worn badly and only worked sometimes...the u-pull-it replaced it easily. Also, check the ground wire on top of the blower assembly...mine was loose and only worked when I pounded on the dash(bad idea). Clean all connections and tighten. If that doesn't work, your motor might be bad, but I've never seen that happen. Good Luck

p.s. was it only the 68 with the round **** controls and then the slide type from 68-72 ?

 

Yep, sounds like excessive corrosion or a bad connection somewhere. I doubt it's the switch, although it's possible. Sounds like it's before the switch going back towards the fuse box. In fact, it could be the fuse box itself having a bad connection to the wire. I had this problem on mine with the wire to the heavy current cig lighter and dome lights. The problem was a flaky connection behind the fuse box. Usually when a fan switch starts to flake out, certain speeds go before others. It usually doesn't just go at once. Only the 67 had the **** heater controls. 68 has the newer type heater plate. The fan switch is a lever on the right side of the plate. Check for a voltage drop from the fuse, and then onwards towards the switch. If the voltage at the battery side of the fuse doesn't drop much, but it does at the switch, then you know it's in the wiring or connections between those two points. The old ford fuse boxes are known for problems once the connections get resistive and then you get heat that starts to build up. I'd almost bet thats where the problem is. I'd bet the wiring is probably ok from the box to the switch. BTW, access to the fuse box, and taking it out is not really easy. The wires behind it will hold it in place for one thing. It's hard to move around even unhooked. Not to mention the contorted position you will be in to work on it... If it's a fuse box fault, knowing my lazy rear, I'd just run a new wire to the fan switch from the battery, or other good high current power source, and use an inline fuse. Not the most elegant fix, but about 500% easier... It wouldn't be anything really noticable to the average viewer... The wires would still be hidden. MK

 

Wayne, you say you have power to the switch. And you are saying that there is no power going through the switch to the blower. Is this true for all switch positions L, M and high? The reason I ask is because there is a resistor set in the circuit between the switch and blower that gives you your low and medium speeds. High speed is a straight connection from the battery through the switch to the blower. This resistor tends to burn out after a few years. It is mounted on the front side of the heater housing and you have to pull the heater back to get at it. What I'm saying is is if you have no fan in the lower two speeds but the high position works, it's probably the resistor. If all positions are dead, it could be the switch or connections.

mike

 

All positions are dead so I will start checking the wiring...at least all leads are pointing that way.

Thank you all for your input on this

Wayne S.

 

I wouldn't be a bit scared to run a temporary switch until it warmed up outside if I was in the cold without a warm place to work. Wiring is not a good place to cut a corner and suffer for the long term.

 

Voltage is a difference in potential measured between two points. If you measure between the input of the switch and a known good ground and get 12VDC with the switch off then measure from the same point with the switch on and your not getting any voltage then somewhere on the blower side of the switch is grounding out the voltage causing no difference of potential. Maybe corrosion, insulation missing or rotted, etc.

 

so far I have not found any corrosion but I did find a pinched wire...my test light would not light up but my meter said I had voltage...which leaves me to guess a broken or almost broken wire in the insulation that is allowing voltage but no amps. Thanks again for the help here in this problem. I would still love to get my hands on a decent wiring diagram for future problems.

Wayne S.

 

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Would one for a 67 be the same for the 68?

 

It might be but never assume anything for a 67 is the same, it is a breed all it's own.

Since most of my temporary fixs end up semi-permanent, I don't reccomend running a wire to the battery for anything. Since the fuse block in these old trucks is woefully inadequate, I would get a good aftermarket fuse block and get one that has a dual feed capability. Run at least a 12 guage(10 would be better) wire from the starter relay hot to one side and use a relay through a key on power source for the other side. Now you have a place to run acessories and reroute other things through.

 

I have to run cables to the battery in my case. None of the truck wiring is large enough for my radios, and also it's much preferred to run straight off the battery as far as an HF radio. The battery acts as a huge cap, and tends to act as a good filter. Less chance of engine/alternator noise problems. Also no extra points of resistance from the radio to the battery. IE: connectors, etc. I run 6 gauge jumper cable wire from the battery to the cab. I also have another one going to the back camper for lighting and radios in the back. I use anderson power connectors on all cable ends and radios and other 12v gear. All the connectors are non gender.
IE: any connector will plug into any other connector, and you can't go the wrong way by accident. The contacts are silver plated and rated for 50 amps at 600v. Back when I usually drove a monte carlo, I kept a second battery behind the back seat for radio use only. All my wiring and connectors are so heavy duty I can actually jump start the car from the 2nd battery without even opening the hood, or getting out of the car. I just unhook the radio, and plug it's power cable into the one from the 2nd battery. And the wiring and connector won't even get warm. I keep a spot for a 2nd battery in the back utility bed box of the truck.
But I agree, for just a fan fix, I'd prefer to keep the wiring in the cab. But being lazy still, I'd probably just run a short clip jumper from the fan side of the fuse on the fusebox over to the fan wire. Bypassing the bad spot on the back of the box. I bet that fuse box is a pain to change out being you have to do it nearly standing on your head or crunched next to the truck in a near fetal position. Not much room to work either. I dread the thought of changing mine...Doesn't look like fun. Maybe it's easier than it looks...
Plumcrazy, As far as the possible crimp, one way to test would be to run a short jumper wire wrapped around sharp pins on each end to stick thru the insulation into the wire and bridge the possible bad spot. That way if it's not the bad spot, nothing is damaged with the wiring. If the fan comes to life, thats the bad spot. But, dunno...I've still got a hunch it's a flaky connection on the back of the fuse box. Mainly cuz I had the same exact thing happen with my cig lighter circuit. I never did really fix it properly. I just jiggled the wire and fuse box until it started working again, and I no longer use my cig lighter much. The dome light doesn't draw enough current to be a problem, only the lighter in my case. I've been thinking about running a fairly high current wire to the lighter, so I can run fairly high current gadgets off of it if needed. IE: laptops, inverters, chargers, etc. To me and my way of thinking, if a wire was hanging by a thread, and then you start the fan and draw a large load, the thread of wire should burn up. That it's intermittant, to me, points to a flaky connection on the fuse box. That won't instantly burn up like a wire. It just gets hot for a second at that point, and gets slightly more resistive due to the arcing and overheating. It's like trying to start a car with the battery cables just laying on top of the posts and not tightened down. Sure, the dome light might work. Until you try to crank the engine, and all goes deader than a doornail... MK