Mechanics

FAN COOLANTS

1999 Cadillac Deville • V8 2WD Automatic •

No the fans do not come on when the compresser comes on
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Jimmy phillips
July 7, 2011.



And the compressor does come on? The PCM controls the three fan relays to give two speeds, low and high. On low speed only the left fan will operate, high speed both fan motors should spin up. If both fans never come on, check first the COOL FNS 50A fuse in the RH underhood fuse block. You will probably have to remove a plastic cover in front of the left strut tower to access this MAXI fuse block. There should be a sticker(legend) illustrating which fuse is which under the cover. If this fuse is not open, check that there is power at/through it. If the fuse is open, the wiring could be shorted, or a fan(s) motor could be shorted causing too much amperage to flow and open the fuse. At this point, compare the resistance of both fan motors. I am not sure what the typical value should be, but I would think that the one with considerably lower resistance is a bad one. If they are the same, the plot may thicken. A fan should definately come on with A/C request and compressor operation, and both should come on at somewhere around 220 degrees(F). If both fans are inoperative, another common denominator is the ground G107 which is bolted to the transmission housing under the thermostat, best viewed from the underside. If you had an open ground at G107, you would have other issues, like no compressor operation, and possibly an ABS fault, but the ground lead from the fans circuit is spliced into the other circuits, so anything is possible. Has this car ever been in a frontal collision? That could play into other causes of the fuse being blown and/or an abnormal ground issue.

Factoryjack
Jul 9, 2011.