#1  
Old 05-27-2020, 01:06 AM
65Bonnie389 65Bonnie389 is offline
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Default 65 Pontiac Heater Not Blowing Air?

Wondering if anyone can point me in the right direction to find an issue with my heater.
Car is a 65 Bonneville, without A/C, have replaced the heater core and seem to have all vacuum hoses and electrical connections hooked up correctly as per the shop manual and all in good condition, not rusted etc.
Also the fuse is ok, the heater hoses are connected and coolant level is good.
I can turn the heater on and all the push buttons work, the blower motor sounds like its blowing and changes speeds with the different control settings right up to high.
The issue is is that basically no air is actually coming out of the vents on any setting. None on the floor, or at the windshield defroster. There is a slight amount of air i can feel coming out but its next to nothing. Is it possible a door in the heater box is not opening when it should, and if this is the case what would be the issue?

Any help appreciated on where to start looking.

  #2  
Old 05-27-2020, 01:48 AM
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Chris65LeMans Chris65LeMans is offline
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You’ll have to pull it out and make sure all the cables are connected to the levers as they should be. Consult the shop manual to see how it oughta look.

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  #3  
Old 05-27-2020, 02:03 PM
Rincon Rincon is offline
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Rats nest in the duct work?

  #4  
Old 05-27-2020, 03:44 PM
mgarblik mgarblik is offline
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If you don't feel any air coming out of the heater box to the floor or up to the defroster vent, there is a door stuck or a link that has detached. There are two vacuum canisters that direct air on that system. One under the hood and one on top of the heater box you can access by removing the glove box interior. If I was working on this, I would find those vacuum actuators and attach a hand held vacuum pump to them and pull a vacuum. See if you have airflow and if the actuators will hold vacuum. The only cable on that system is the temperature control. If you have no airflow/hot or cold, that's not the issue. Good luck.

  #5  
Old 05-27-2020, 06:20 PM
65Bonnie389 65Bonnie389 is offline
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Quote:
Originally Posted by mgarblik View Post
If you don't feel any air coming out of the heater box to the floor or up to the defroster vent, there is a door stuck or a link that has detached. There are two vacuum canisters that direct air on that system. One under the hood and one on top of the heater box you can access by removing the glove box interior. If I was working on this, I would find those vacuum actuators and attach a hand held vacuum pump to them and pull a vacuum. See if you have airflow and if the actuators will hold vacuum. The only cable on that system is the temperature control. If you have no airflow/hot or cold, that's not the issue. Good luck.
Thank you for the reply, i was thinking that it must be some sort of vacuum issue, as everything else has been serviced when i had the car apart and put back correctly. I will check out those vacuum diaphragms and hopefully sort out the issue. Do those vacuum diaphragms wear out over time, if i need new ones I hope they are reproduced?

  #6  
Old 06-08-2020, 08:04 PM
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pfilean pfilean is offline
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Sounds like maybe your system is one that is vacuum control not cable control. There is a vacuum "router" in the heater control (behind the slide levers and blower switch) that begins to leak with age. Are a crap shoot to get them to reseal. As a quick test to see if the vacuum controlled door is working or not just take off the vacuum diaphragm on the heater duct in the engine compartment and move the little lever to see if you can open the door by hand. If that tells ou anything then you may also want to test the vacuum diaphragms with a piece of hose connected to each diaphragm and just suck on the hose. You can get enough vacuum that way to see if all the diaphragms work. If you chase the problem down to the "router" in the control good luck. Most of those old parts are unobtainable.

  #7  
Old 07-06-2020, 08:58 PM
65Bonnie389 65Bonnie389 is offline
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Quote:
Originally Posted by pfilean View Post
Sounds like maybe your system is one that is vacuum control not cable control. There is a vacuum "router" in the heater control (behind the slide levers and blower switch) that begins to leak with age. Are a crap shoot to get them to reseal. As a quick test to see if the vacuum controlled door is working or not just take off the vacuum diaphragm on the heater duct in the engine compartment and move the little lever to see if you can open the door by hand. If that tells ou anything then you may also want to test the vacuum diaphragms with a piece of hose connected to each diaphragm and just suck on the hose. You can get enough vacuum that way to see if all the diaphragms work. If you chase the problem down to the "router" in the control good luck. Most of those old parts are unobtainable.
Thanks for the replies, turns out it was the vacuum diaphragm on the heater box in the engine compartment, the rubber inside had completely turned to dust.
I actually had a spare one i pulled from another car years ago which was in good shape, so swapped it out with the good one and now works like new!
Interesting to learn something about these old vacuum operated heater systems, as this is the first one i have worked on.

  #8  
Old 07-07-2020, 10:21 AM
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pfilean pfilean is offline
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Probably wouldn't hurt yo replace the vacuum lines also if you haven't already . They get splits and cracks that are hard to locate. I did mine and even got some paint markers from an art store and put the original color stripes back on.

  #9  
Old 07-08-2020, 09:13 PM
65Bonnie389 65Bonnie389 is offline
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Quote:
Originally Posted by pfilean View Post
Probably wouldn't hurt yo replace the vacuum lines also if you haven't already . They get splits and cracks that are hard to locate. I did mine and even got some paint markers from an art store and put the original color stripes back on.
Yes, that's a good idea, will grab some new vacuum hose and get that in as well, amazing it still works after all these years.

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