I've replaced the blower motor , still nothing. no dtc. at the blower motor plug , there's 2 ohms to ground on black,12v on red and 4 to9 volts on white, depending on blower speed with engine running and warm. what do I check next? If the acm is bad would it have any voltage on the white wire?I don't have a cadillac scan tool.
Blower Motor Inoperative at Any Speed (Front) ?
The heater & A/C programmer is probably the problem . The 4 to9 volts on white - that's not how you test that circuit . That is a PWM - pulse width modulation circuit . The programer switches that signal on an off real fast . You need a automotive lab scope to see the square wave that would be produced .
HVAC Blower Motor Circuit
SOURCE: 1999 cadillac deville blower dont
red black and gray are just half the connections. Red is positive 12 volts coming from fuse of circuit breaker. The black wire is either the ground or the main hot wire going to the blower motor (3 pin connection only), and the gray wire (if is is small in size) is a variable voltage coming from the body control module requesting speed for the blower motor.The blower control module varies voltage on the main wire going to the blower motor, supposedly in accordance with the requested voltage from the body control module. Usually if all fuses are okay and present on the apprpriate wire of the blower control module, the a blower motor that will not run or stays running after the key is turned off is the fault of the blower control module. If the blower control module has failed the the cause must be determined (over amping blower motor) or else new blower control module may fail when powered up.Usually blower control modules have more than three wires. Usual connections are: B+ (battery voltage) GND (chassis or engine ground), two large wires going directly to blower motor (can be any color, but are usually 10 guage in size), and an optional wire that reports voltage level back to the body control module.
SOURCE: i have only low speed on the blower motor for
on the housing under the hood where your heater core and AC plumbing is there is a plug in rheostat that you need to remove and replace-take it off with the two screws that hold it and take it to a napa and they will sell you the replacement for about $20. Good Luck!
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Ohm testing a wire is no good , the wire could be damaged inside (corrosion) an have just one strand ,would show same resistance as a fully intact wire . Loaded circuit testing is the correct way , current flowing . Use a sealed beam headlamp with the correct wire gage. Hook to the B+ side an ground of the blower motor connector . If the light shines bright the power an ground circuits are good . If dim ,has resistance in the circuit . Go on youtube an watch videos on voltage drop testing .
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