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99 Deville
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5 Posts
Discussion Starter #1
I'm at the same place. Mine blows only cold air. No codes.

I have the service manual, it wants me to do the following:

Use a scan tool override while monitoring the feedback value. Command the door to these positions...

So I dug into scan tools including used ones that should work on a 99 Deville. I might as well dig in a swamp. It seems like a used $150 pro tool should do this, but heck if I can figure out what old tools actually do what. Any guidance?
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,059 Posts
I'm at the same place. Mine blows only cold air. No codes.

I have the service manual, it wants me to do the following:

Use a scan tool override while monitoring the feedback value. Command the door to these positions...

So I dug into scan tools including used ones that should work on a 99 Deville. I might as well dig in a swamp. It seems like a used $150 pro tool should do this, but heck if I can figure out what old tools actually do what. Any guidance?
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the HVAC system on a 1999 Deville is completely different than a 2000+ Deville -
vacuum controls the MODE -
electric actuators control the temp -

if you are getting COLD on BOTH sides -
AND you have NO "B" codes -
you probably have a clogged heater core -

simple way to verify this -
with the engine at operating temp -
set the cabin temp to 90* -
blower on medium speed -
grab the 2 heater hoses where they go through the firewall -

BOTH hoses should be equally HOT - too hot to hold for more than a few seconds -

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regarding the scan tools - don't waste your money - you don't need one -

FIRST -
MOST scan tools are ONE-WAY-communication -
meaning they can only RECEIVE information from the car's computers -

the only 2-way communication scanners that I know of
are the VERY expensive TECH2 and a SnapOn model -

SECOND -
using a scan tool to override the various MIX DOOR actuators will only verify what the DTC's already told you -
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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19,059 Posts
thx, you made me realize I never checked the passenger side, which is hot.

It's the driver's side actuator.
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you need to actually visually inspect the actuator -
it is not uncommon for the connecting rod to disconnect from the actuator arm -
this could explain the lack of codes -

IF the actuator arm IS connected - and the actuator IS defective -
you need ACDELCO 15-72215 - best price I found was $70 - with free shipping -

or $77 - with free shipping - on Amazon -
 

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Registered
99 Deville
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5 Posts
Discussion Starter #5
Yeah, easy to get to for the driver's side, my lack of heat was solved via a manual sliding of the door. New part arrives tomorrow to keep it automatic, an easy fix on this one. I actually got it for $63 direct from Dorman on Amazon.
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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67,924 Posts
Your posts have been moved to their own 1999 thread from the other thread that you hijacked.
 

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I gambled with the cheapest replacement on this one when mine went out, I believe the one that had a heart on RockAuto - it was fairly easy to access through the glove box hole. Opened the broken one up and there was nothing much inside, and it gave me confidence that a very cheap one will probably still work fine. It still works to this date.
 
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