Friends of the Professional Car Society - Official Website of the Professional Car Society, Inc.Friends of the Professional Car Society - Official Website of the Professional Car Society, Inc.

Go Back   Friends of the Professional Car Society - Official Website of the Professional Car Society, Inc. > Professional Car Discussion > Technical Discussion Forum

Technical Discussion Forum For the discussion of technical questions about Professional Cars and their repair and maintenance. Posting in this forum is limited to PCS Members and / or Site Supporters. We encourage all website users to become members of the Professional Car Society and / or become Site Supporter.

Thread Tools Display Modes
Old 08-11-2019, 05:29 PM
Nicos Elias Nicos Elias is offline
PCS Member
Join Date: May 2013
Location: Allentown PA 18104
Posts: 32
Thanks: 54
Thanked 48 Times in 22 Posts
Groans: 0
Groaned at 0 Times in 0 Posts
Default '73 ambulance heat

Last time I drove my '73 Superior Cadillac, super-hot air was blowing into the driver's area from the climate control, even when off. If I turned it on, it would blow harder, and it's like oven-hot. Moving the temp. dial didn't change anything. Very uncomfortable and possibly dangerous? How do I stop it?
Reply With Quote
Old 08-11-2019, 06:21 PM
Peter Grave Peter Grave is online now
PCS Member

Join Date: Jul 2009
Location: Ottsville PA 18942-0250
Posts: 907
Thanks: 1,594
Thanked 2,154 Times in 1,202 Posts
Groans: 0
Groaned at 0 Times in 0 Posts

The issue is probably a vacume hose on the Climate Control system somewhere. My 96 Limo you can;t shut the heat off no blower problem after searching now in the spring I bypass the heater by hooking the in and out hoses together this bypasses heater core. In your case I would pull the blower fuse and do the bypass on the heater hose trick. Then start tracing the vacume hoses looking for pinched unhooked or broken.
Reply With Quote
Old 08-11-2019, 06:29 PM
Bill Leverett's Avatar
Bill Leverett Bill Leverett is offline
PCS Member/Super Site Supporter/Paramedic Supervisor
Join Date: Mar 2009
Location: Mill Bay BC Canada
Posts: 658
Thanks: 1,830
Thanked 1,094 Times in 378 Posts
Groans: 0
Groaned at 1 Time in 1 Post

I had the same sort of issue with my '73 Lifeliner. As Peter mentiond it's most likely a vacuum hose leak. These vacuum hoses control the blend of hot and cold air by opening/closing shutters in the system.

Having taken the dash apart on mine to fix some dash lights let me tell you that there is a multitude of vacuum hoses that come off a central point. If I recall correctly, something like 8 separate lines. If you are lucky it's just a hose that has come off and can be popped back on. If not, tracing a leak is a big job. Paul can give you some good advice on this. I'd be looking to replace all of the lines with new rubber. If you have a leak in oneline you'll likely develop leaks in the others.

Best of luck withthe fix.
Bill Leverett

1953 Pontiac/Barnette Combination
Reply With Quote
Old 08-11-2019, 10:48 PM
John ED Renstrom's Avatar
John ED Renstrom John ED Renstrom is offline
PCS Member - Elected Director 2017-2020
Join Date: Mar 2009
Location: Hot Springs SD 57747
Posts: 11,693
Thanks: 4,175
Thanked 15,115 Times in 6,388 Posts
Groans: 2
Groaned at 3 Times in 3 Posts

The shop manual has a decent flowchart that is a big help. Most people jump on the vacuum shut off valve but really it only closes when the system is on max air. A stuck flaper will do the same thing. Remember on this system the blower does not shut off. First place to check is under the hood the main vacuum line on the engine is a known problem. Next is the servos inside on the heater box. Some big foot is always knocking one of them off. Default mood is set for the system to go to defrost if the controller is bad. So if its just blowing hot air. Do as suggested First. It most likely the blend door unless your ac system is out of freon. As it uses heat and cold to give you the set temp.
drop in for coffee anytime
Reply With Quote
The Following 2 Users Say Thank You to John ED Renstrom For This Useful Post:
Bill Leverett (08-11-2019), Steve Loftin (08-12-2019)

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
heat risers FYI Mike Stevens Technical Discussion Forum 15 03-22-2012 10:25 AM
check those heat risers John ED Renstrom Technical Discussion Forum 12 09-09-2010 11:28 PM
no heat Josh Horton Technical Discussion Forum 9 01-12-2010 06:44 PM

All times are GMT -4. The time now is 06:48 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright 2009 - 2018 Friends of the Professional Car Society