blower motor dosn't blow on heat or max a/c

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72_dart

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Ok I just finished rebuilding my a/c heater box in my 72 dart with a slant six. While I had everything out I replaced the heater switch. Actually this is a 2 part questions that may be related. There is what appears to be a brown (ground wire?) That is attached to the hold down for the heater core.... I don't remember where the other end was supposed to get attached. The other question is what could I have possibly hooked up backwards that will make blower not run in the heat or max a/c position?

Like always any help is greatly appreciated.
Sincerely, John
 
Donno. The wiring diagrams for AC stuff is not in the wiring section, as a rule. It's in the back chapters on "heaters and air conditioning"
 
Thanks, I was looking at a diagram that you supplied me with. But I dont see anything that would allow the blower motor to work on defrost and ac but not on heat and max ac. Ive looked it over several times and just dont seewhat it could be. Would a bad heater switch cause this???
 
Yup... the contact pairs are there for 4 positions (all but OFF) and any of the 4 phosphor bronze contact pairs can get messed up causing that position to not work. These tend to corrode and get reeeealy hot (what with the high current draw of the blower) and melt the plastic and so sometimes a set of contacts will melt out of alignment with the wiper.

You might have luck if you cut off the little plastic 'rivets' on the back of the control/switch, carefully removing the back cover, and see what is melted/corroded and see if it can be fixed. I fixed all but one postion in my control in this way. Use epoxy to re-attach the back when done if you are successful. There is a 'sticky' thread here on a rebuild.

Classic Industries advertises replacements; not sure how available they are though.
 
Thanks I might try that i just baught the switch from the old car parts northwest guy on ebay. I figured it was NOS so it should be good right? well i know its damp in the northwest and it wasnt in plastic so that makes sense. man i dont want to take that switch out again that was an SOB with my big arms. what is it that gets cleaned inside the switch? I did have 1 apart before but I dont remember how it worked. it just looked like a bunch of mountian shaped cutouts.
Thanks again.
 
The 'mountain shaped' pieces are the 'cams' so to speak that move things around. Look at the sticky thread at the very top of this subfroum; it has lots of good pix of theis switch taken apart. You ought to be looking at cleaning up the copper pieces.

I would be rather surprised that the NOS switch from OCPNW did not work. But, the grease could get old and not allow the parts to move around properly. Does it move smoothly from position ot position?

Let me ask; does the blower work in ANY position (like defrost)?
 
I hope this can give some help

It's not for a 72
 

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There should be a ground wire with ring terminal that attaches at a sheet metal screw behind the right kick panel.
 
Sorry I've been traveling for work. Yes nm9stheham the switch does work in 3 of the 5 positions. Defrost and a/c and of course off all work. When the switch is in max a/c or heat nothing happens. The doors don't move and the blower motor will just stop.

Thanks redfish that's right I couldn't remember where I unhooked it from.
 
The answer to your problem HAS to be "right in the switch"
 
Hmm if the doors don't move, it almost sounds like the mountain shaped 'cams' are not moving freely and not allowing things to move properly. They shuttle the vacuum 'thingie' back and forth to route the vacuum for the door movement. (Sorry for the high tech talk there lol...)

But the blower contact on each position depends on the button you have selected being pushed in far enough, so something is stopping some of the buttons from moving in as far as they should (old grease?) OR the contacts are tarnished badly. Try pushing hard on one of the non-working buttons and wiggling it around. Still sounds like you need to get it out and work on it.
 
The old switch everything worked but the buttons didn't move smoothly and didn't fully push all the way in when I took it away the mountain shaped cutouts were rounded out so I figured that it wasn't fully canceling out before the next button gets pushed. The new switch seems to work like it's full of butter (real nice). When I get home in a few days I'll try to take the switch apart and clean the contacts. Out of the whole job that is the part that I had the least amount of fun with (contorting my arms and scraping up my arms on sharp tight spots just to remove 2 screws. Either way I want it all to work so I'll do it.

Also didn't mean to make it sound like is was bashing OCPNW, I haven't ordered much from him but have been really happy with him reasonable prices and supper fast shipping I would not hesitate to buy anything from him.
 
While in there, consider adding a relay that actuates in the "blower hi" switch position (to keep the high current out of the switches). I did that long ago in my 69 Dart after replacing the expensive 5 button pneumo-switch. Otherwise, the new switches will eventually melt too. Those button switches are priced like gold today.
 
Thanks for the tip Bill. If I wanted to use a relay to feed the blower on all three positions would I need 3 relays or could it be done with one? Also you were the only one that responded to another thread asking the difference in these switches. Is it possible that the switch I'm using is different and just not compatible? I was lazy this weekend so I haven't taken it out to clean the internal contacts.
 
Yes. You would need a separate relay for each blower speed position (L-M-H). However, I think only the high position has much risk of melting the speed switch and push-button switch, so that is the only position I added a relay. The other positions have series resistors that limit the current.

I don't recall your other post. There were several blower speed switches, over years and even bodies in the same year. My 69 Dart had a chrome steel switch you slide horizontally. Behind the scenes was a lever and fairly standard sliding electrical switch. I picked the switch open and added cut teflon behind the slider to replace the melted plastic I found, as I recall.
 
Yup, that's what it was. Opened up the switch pulled out all the contacts, threw them in my tumbler with crushed walnut for about an hour and they weren't the same color. Before they looked like brass. Now they are shiny silver. Before I screwed the back on I hooked everything up in the car and made sure that everything worked. Which it did. Now to putting it back in.
Thanks all for the help. It's greatly appreciated. I thought with a new switch I would be safe but it turns out that these even though new are actually quite old and could use a little cleaning.
 
The grease deteriorates. A real problem with older electronics
 
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