1998 S90 EEC fault code 151

dmg4 · Post by **dmg4** » 28 Dec 2014, 08:44

The Electronic Climate Control/AC switch has been flashing, indicating a system fault. The blower motor does not operate when this happens. The problem is intermittent, and more common in damp or rainy weather. If I restart the car after a few minutes of running, the fault may clear and the system (both AC and heat) work perfectly.

Going through the diagnostic procedure on the attached pdf, I consistently get the fault code 151: Alternator (D+ signal fault), and no other fault codes.

Any suggestions on what to do next? What are the likely causes of the code, given the above symptoms?

Frogestil · Post by **Frogestil** » 29 Dec 2014, 11:15

Does this only happen with the knobs on auto or can you force the blower to run by taking it off auto and adjusting blower speed?

dmg4 · Post by **dmg4** » 29 Dec 2014, 15:06

The blower does not operate if the fault light is flashing, irrespective of the switch position. I can still get some heat by following the instructions in the owners manual: set fan speed to "0", and air flow to "vent". As long as the car is moving, there will be a slight amount of warm air coming out of the dash vents.

There are times when the blower motor pulses on and off, as if there is a bad connection to the blower motor. This does not occur while the fault light is flashing, and the pulsing never lasts more than a second or two, and then the system goes into "fault" and shuts down.

93Regina · Post by **93Regina** » 30 Dec 2014, 11:53

dmg4 wrote:fault code 151: Alternator (D+ signal fault)

Homework Assignment: Charging System Tests

I know nothing of this newer stuff, but this author explains and shows how to test those alternators with D+