1972 Duster Heater Control Unit - defrost question

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TKoers

TKoers

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Hello,

I'm new to the A body world as my dad just gave back a car my brother and I got him for father's day 8 years ago as he can no longer work on it.

I am trying to get the defrost working in the car. I pulled the heater control unit out (that wasn't easy but it made it through the radio slot) and discovered that whomever owned the car previously had been trying to rig the temperature control cable to the adjustment switch through some sort of what appears to be soldered connection assuming to a vertical post riveted to the control lever itself (you'll see that in the cable picture below). That of course did not hold so I have to find a way to re-connect it just to be able to pull heat to the defroster when needed. You'll see on the lever picture the riveted post (numbered 1), the missing piece I assume was for AC control as it would only be activated when the temp lever was all the way on cool (numbered 2) and lastly a hole where the temperature control cable retaining clip was screwed into (numbered 3). The car was originally a slant 6 with AC but who knows when the AC was pulled out and that's fine as I'm not looking to reinstall AC in the unit - just want to be able to move the temp to hot if needed for defrost. The control unit has a broken nipple and I can't find a vacuum diagram. I am wondering if anyone knows what the broken nipple was for and if it is for AC only or if it will prevent the defrost from working assuming I can find a way to reattach the temperature control cable to the adjustment lever. Thanks in advance for any help you can provide.

TempControlCable.jpg


BrokenVacuumNipple.jpg


RivetedPostOnControlLever.jpg
 
Hi! Thank you for this topic, I've been fixing it lately, so I'm looking for similar topics, for which thank you very much
 
TKoers said:
Hello,

The control unit has a broken nipple and I can't find a vacuum diagram. I am wondering if anyone knows what the broken nipple was for and if it is for AC only or if it will prevent the defrost from working assuming I can find a way to reattach the temperature control cable to the adjustment lever. Thanks in advance for any help you can provide.
Click to expand...

Go to MyMopar and download (free) the 72 Plymouth chassis manual (factory service manual). Down through about 24-50, and especially page 24-63

Several of the manuals over there came from the guys right here
 
I think that the push button dash vac module is available on eBay.
 
67Dart273 said:
Go to MyMopar and download (free) the 72 Plymouth chassis manual (factory service manual). Down through about 24-50, and especially page 24-63

Several of the manuals over there came from the guys right here
Click to expand...

Thank you 67Dart273 for the call out and recommendation.

The chassis manual is an incredibly useful tool.

On page 24-64 there is a diagram that shows the vacuum ports in a configuration that reflects what the 3502414 control switch looks like and according to that picture it appears that on my switch the broken port is number 2.

I have sourced a replacement unit from Ebay which is in rougher shape than my existing one but the switch has no broken ports so I'll try swapping those out.

Again, appreciate the feedback.
 
A question for anyone. He says his car is a 1972 duster, but all his photos are ac parts from 1973 thru 1976 dusters. ???
 
Last edited:
townsend said:
A question for anyone. He says his car is a 1972 duster, but all his photos are ac parts from 1973 thru 1976 dusters. ???
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I have only started working on the car and pulled this out without too much trouble but what makes you think the heater control unit isn’t the right one?
 
3502414 control switch was only used on 73 thru 76 Valiant ,Darts and Dusters. How about posting the month and year of manufacture on the left door decal.
 
townsend said:
3502414 control switch was only used on 73 thru 76 Valiant ,Darts and Dusters. How about posting the month and year of manufacture on the left door decal.
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Wow - thanks - that's interesting that that switch was only used on 73-76's... Appreciate the update. Perhaps the person in CO where this car originated from had swapped out the original heater control unit for a 73-76 model as you've indicated. The unit fits in dash fine and the fan works - it's just that the temperature control cable wasn't connected to be able to defrost the windows. Attached is a pic of the side of the unit too.

There is no left door decal since the car was restored in CO. All I have is the VIN on the car and the title that shows it's a '72. Maybe the 73-76 units were interchangeable with the 72's... You wouldn't have a picture or switch number for the 72 model by chance would you? I'm not trying to restore the car to factory originals - it's a clone car (was a slant 6 with a column shifter but the guy in CO who restored it dropped an '84 360 in it and moved the shifter to the center console...

Thanks

HCU Switch Number.jpg
 
Ok, lets take this one step at a time. Go to mymopar and look at the 72 Mopar parts catalog. On page 6 you'll find how to decode the body plate. That will show the date information. Hopefully the body plate will still be on the left inner fender.
You're complete control switch and multi pin rubber vacuum hose connector are from 73-76 Dusters. Very different from the 72 and earlier models.
Pictures of the ac control can be found on the hamtramck registry site. Once there click on library, then under dealership data books click on 72 plymouth image, then valiant/duster. Scroll down and you'll find photo of the ac/heater control switch. Do the same for the 73 model year. There's other useful info on this site.
 
Thanks for the referrals. I’ll check those sites out. Unfortunately there is no fender tag on the car. We only have the VIN and I haven’t come across any broadcast/build sheet that I often see people find behind their rear seats or somehow in the dash.

Hopefully between the sites you shared and the network here I’ll find a way to get the defrost working.
Thanks again
 
Let's try to identify the complete dash. Give us photos of the left, center and right sections of the dash.
 
townsend said:
Let's try to identify the complete dash. Give us photos of the left, center and right sections of the dash.
Click to expand...

I appreciate the helpful references above. After reviewing them, it appears that the control unit in my 72 is from the 73+ year model and that likely explains the way it was jury-rigged. I have obtained another control switch with all of the plastic vacuum nipples intact and I'm going to swap it out and see if that will get the defrost working again.

Thanks again for the references @townsend!
 
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