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Discussion Starter #1
Hello guys, I have a 1991 DeVille with a converted ac to r134. The problem I got is very strange when I start the car after it has sitting for a while the ac blows cold and works but when I’m driving in the city or the car stays in one place with engine on the ac shuts off. When I drive in highway after a while it starts to work again. What is this kind of strange thing going on. Pleas help Br
 

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2001 eldorado,2008 DTS,2005 XLR, '96 eldo,'95 eldo,' 89 eldo,'78 eldo,'11CTS-V
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What shuts off; the HVAC blower fan, or the compressor?
 

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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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there are several sensors and devices that are designed to disable the compressor for a number of reasons -

from your description - I suspect that the freon is getting too hot -
or you have a faulty freon temperature sensor -
OR -
you might have a freon over-pressure condition -
or a defective pressure sensor -

check for codes -
 

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Discussion Starter #5
there are several sensors and devices that are designed to disable the compressor for a number of reasons -

from your description - I suspect that the freon is getting too hot -
or you have a faulty freon temperature sensor -
OR -
you might have a freon over-pressure condition -
or a defective pressure sensor -

check for codes -
Thanks but i have no codes I have checked it. but is there any other way to check the things you tell me and What do you think is the solution for this br
 

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White Diamond '03 DHS (with DTS floor shift)
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Excessive clutch gap would prevent the clutch from engaging, but would not disengage it once engaged.
 

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Discussion Starter #11
Does someone know where to buy pressure sensor I have searched but it seams that it’s hard do find?
 

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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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Does someone know where to buy pressure sensor I have searched but it seams that it’s hard do find?
=======================
they are next to impossible to find here in the US -
there are no new ones - used it your only hope -
 

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Discussion Starter #13
=======================
they are next to impossible to find here in the US -
there are no new ones - used it your only hope -
I’m screwed, is it possible to use a universal or something or can I change something else in the system so I can have another pressure sensor or does it have to be original 😥
 

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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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19,863 Posts
I’m screwed, is it possible to use a universal or something or can I change something else in the system so I can have another pressure sensor or does it have to be original 😥
============================
it must be the correct part -
the same pressure switch was used in ALL Cadillac models from 1987 through 1993 -
 

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Discussion Starter #15
Ok thanks then I know. Basscatt is the high and the low pressure the same in the 1991 Deville and is this the one in the picture
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73A572A7-D1EB-405B-BEF0-BD95A594205A.jpeg
 

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92 Fleetwood 2dr cpe - FWD, 96 Seville SLS, 02 Seville
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Get yourself a full set of guages. Hook em up and monitor while idling. Post static pressure and pressures when the compressor shuts off.
 

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Discussion Starter #17
Get yourself a full set of guages. Hook em up and monitor while idling. Post static pressure and pressures when the compressor shuts off.
My English is little bad I’m from Sweden what do you mean by “Post static pressure and pressures when the compressor shuts off”
 

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92 Fleetwood 2dr cpe - FWD, 96 Seville SLS, 02 Seville
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When guages are hooked up, car or AC off, the pressure will equalize with low and high showing the same pressure - static.

Turn on the ac, low should drop to somewhere in the 30-40 psi range and high will get over 175 psi. The pressures might keep moving around. Watch the guages looking for the point where the compressor shuts off, the pressures will start to move back to static.

Try this with doors and windows closed. And again with doors, windows open. (The test with Windows is to observe if the temp sensor in the passenger compartment is influencing the control of the compressor).
 

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Discussion Starter #19
When guages are hooked up, car or AC off, the pressure will equalize with low and high showing the same pressure - static.

Turn on the ac, low should drop to somewhere in the 30-40 psi range and high will get over 175 psi. The pressures might keep moving around. Watch the guages looking for the point where the compressor shuts off, the pressures will start to move back to static.

Try this with doors and windows closed. And again with doors, windows open. (The test with Windows is to observe if the temp sensor in the passenger compartment is influencing the control of the compressor).
Thank you good suggestion I’ll try that 👍🏻
 
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