Lincoln/Mercury Repair: HVAC EATC Blower Speed, automatic temperature control, mercury mountaineer

Question
I have a 2000 Mercury Mountaineer with the digital HVAC automatic temp control and I only have high blower speed. I ran the self-test and received a code 888, which is supposed to mean no internal system problems.  I installed a new blower motor relay in the power distrib box #1.  The owner's manual doesn't show the auxiliary power relay dist box on the right side of the passenger compartment, under the air cleaner box.  There are relays in the box and I read where one controls power to the blower speed controller.   Can you tell me which relays I should check there, or elsewhere?  Also, do any of the PCM relays control power for the EATC that could be the problem?  Thanks

Answer
Hi Don,

No, not the relay, if it was bad you would have no fan. Two things here that will cause this.

The heater blower motor switch resistor has the following features:


The assembly is located on the evaporator housing in the engine compartment.
Three resistance elements are mounted on the resistor board to provide four blower motor speeds.
Depending on the heater blower motor switch position, series resistance is added or bypassed in the blower motor circuit to decrease or increase blower motor speed.
An overheating protective device (thermal limiter) will open the resistor coil circuit when the temperature reaches 121°C (250°F) interrupting the blower motor operation in all speeds except HIGH.
The thermal limiter cannot be reset and is not serviceable.

Or

Article No.
00-11-2

May 29, 2000

^ AIR CONDITIONING - BLOWER MOTOR STAYS ON
HIGH - EATC VEHICLES ONLY

^ AIR CONDITIONING - TEMPERATURE DOES NOT
MAINTAIN SETPOINT - EATC VEHICLES ONLY

FORD:
2000 CROWN VICTORIA, TAURUS
1999-2000 EXPLORER

LINCOLN:
2000 LS, TOWN CAR

MERCURY:
2000 GRAND MARQUIS, SABLE
1999-2000 MOUNTAINEER

ISSUE
On some vehicles equipped with Electronic Automatic Temperature Control (EATC), there may be concerns where the blower motor may stay on high after desired temperature is reached, where temperature control does not maintain setpoint, and/or where the temperature gradually wanders away from the setpoint.

ACTION
Refer to the following Service Procedure to aid in normal diagnostics of the EATC system.

OTHER APPLICABLE ARTICLES: NONE
WARRANTY STATUS: INFORMATION ONLY
OASIS CODES: 208000, 208100, 208200, 208300, 208999


This would mean you would need to replace the EATC in the dash.