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1999 DeVille Concours
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5 Posts
Discussion Starter #1
I am having an issue with A/C not blowing cold air.

I checked fuses all good. I pulled A/C Comp Relay and jumped the socket locations to check if clutch would engage.... It does.

So I know that the electromagnet and clutch work, also the compressor.

I need to know what voltage/ohm reading (if it any) I should have at the HIGH and LOW pressure sensor switch when the connector is unplugged.

The fans at the radiator work, I see them come on.

What other devices other than the ECM would be affecting the A/C to not blow cold air?
 

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98 DeVille, 97 DeVille d'Elegance
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7,345 Posts
Check for codes first off, the low ajd high sensors rarely go bad. Need gauges to check pressures as if freon low compressor will engage unless very low.
Other issue may have a door issue in the car if won't switch from hot to cold.
 

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Super Moderator
2010 DTS
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87,398 Posts
Follow Rodnok's advice and pull the DTC's first. You may simply be low on refrigerant. Low refrigerant will disable the compressor to protect it.
 

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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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20,082 Posts
I am having an issue with A/C not blowing cold air.

I checked fuses all good. I pulled A/C Comp Relay and jumped the socket locations to check if clutch would engage.... It does.

So I know that the electromagnet and clutch work, also the compressor.

I need to know what voltage/ohm reading (if it any) I should have at the HIGH and LOW pressure sensor switch when the connector is unplugged.

The fans at the radiator work, I see them come on.

What other devices other than the ECM would be affecting the A/C to not blow cold air?
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you are over thinking and over diagnosing this -

there are safety systems built into the AC system to protect itself -

these systems are all monitored -
and if a component fails -
a specific code is set -

STEP 1 - always -
check for Diagnostic Trouble Codes -
if you don't know how - go here and read the ENTIRE post -

http://www.cadillacforums.com/forums/cadillac-deville-1985-2005-including-1985/138257-how-pull-codes-dtcs.html

if you have any codes - post them here -
ALONG WITH THEIR DEFINITIONS -

----------------------

you will probably find a low freon code -

that will narrow down the problem
to either a faulty low pressure switch - doubtful -

or you are in fact - low on freon -

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clear the codes -

connect an AC gauge set -

start the engine -

report the pressure readings for BOTH -
the high side and low side -

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oh - jumping the compressor relay is a bad idea -

freon carries the oil that lubricates the compressor pistons -

forcing the compressor to run with a low freon charge
will starve the compressor of oil and destroy it -
 
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