heater trouble

[1970shortwide]

What's going on fellas? I got a 1970 chevrolet c10, who is giving me electrical problems. Its my daily driver and my pride and joy.......some of the time. I have bought a new engine wiring harness, a new front engine wiring harness after the old one caught fire. New starter, alternator, voltage regulator, and new battery. She is running like a champ but now since its starting to get cold I decided to try to hook my heater up. I bought a new heater core, new heater wiring harness, new heater control unit. And new vents. I have hooked everything up but the blower still doesn't turn on. I have a shop manual I bought but it does nothing for me with the wiring diagram on the heater. I don't know how the fan switch gets power and if it does how does it fit in the harness? I have replace fuses and all kinds of junk and still nothing! Please somebody help me! Any information will help. Thanks guys

[john]

Welcome to the board. Does your truck have A/C?

[69GMCLonghorn]

I'm going to assume you DON'T have A/C, mainly because I couldn't help you if you did... Here's what I would do:

Run a jumper directly to the blower fan connection from a 12 volt source that you know is hot. See if the fan comes on. If it doesn't, run an additional jumper to a good, solid ground, and see what happens. I had a really bad problem keeping mine grounded. I ended the problem by running a ground wire to the negative post on the battery. It worked like a charm.

If the hot side is the problem; It has to run back to the fuse block at some point. That is where the fuse is. You should be able to trace (with your diagrams) the wire out of the fuse block and see where it goes. If there isn't one, then run one, hook it up properly and you should be good to go!

[PanelDeland]

There is also a resistor on the right side under the dash.If it is bad it can cause speed problems and may be able to cause a no run situation.

[oldblue1968chevy]

mine doesnt blow very hot, i cleaned the rats nests from the heater core area. But still doesnt blow hot, our 53 chevy belair blows hoter than my truck. I just have steel floors btw. whats my problem

[1970shortwide]

I don't have a/c. I also read the wiring diagram and there is a brown wire that runs from the fuse box to the heater bracket thing. I am 99% sure that wire is no good, and I don't have the money for a under dash wiring harness. Is it possible to run a wire from let's say the radio part of the fuse box to the heater harness, would that work? Another thing if that does work where exactly does it go to connect to the heater harness? I see picture of a wire running to the harness but there is not a good view or instructions on how it actually connects to the harness. And seriously thanks for all the advice guys! Its just been me and my dad trying to figure this stuff out and now having the knowledge and experience from you all really helps.

['68 C-20]

oldblue1968chevy , Have you ever flushed the heater core? But I think you might want to start a new thread with your problem, It will get better visibility.