Chery A21 2005, Service Manual, Page: 268 / 475

The A/C switch open, blower switch open , the A/C pressure is normal, the
evaporator temperature sensor detects the correct data, the A/C requirement signal is
sent to ECU via these switches. After receiving the signal, ECU controls the A/C relay
to close and sends the speed increasing signal to the stepper motor at the same time,
and start the electric fan, then the A/C system will start working.
The battery supplies power to electric fuel pump through fuel pump relay, the relay
can only p ut through the electric fuel pump circuit when startin g or the engine is run ning.
When the engine stop running accidently, the fuel pu mp will also stop automatically.
M
V
70
86 30
85 87
FB16
15A
Fuel Pump
Relay
ECU
Loud noise when running 、 can not well accelerate 、 can not
start （ start difficult ） and etc.
For t he using of bad fuel
1
． Colloid accumulate and form insulated surface
2 ． fuel pump b ushing and armature locked
3 ． fuel sensor unit erode.
（ Remove the pl ug ） set th e multimeter at the ohm position,
connectin g the two pens to the two pins of fuel pump, test the inner resistance, it is not 0
or
（ that's to say it is not short circuit or op en circuit state ） .
（ Connect the plug ） connect the fuel pressure gauge at th e oil intak e pipe, start the
engine, ch eck whether the fuel pump work; if it is not work, check the “ + ” pin t o see
whether th ere is power voltage; if it works, observe the working conditions of engine to see
whether th e fuel pressure is about 300kPa.
:
Fault description
Trou bleshoot
：
Fault analysis ：
：
（ ） Fuel pump relay
3
Figure9-18 Fuel p ump relay circuit di agram
（ 4 ） A/C relay
69
ECU
1 ． The blower mot or fault （ fuse burnt, relay circuit open circuit or short
circuit ）
2 ． The A/C pressure is abnormal （ high pressure is too high and low pressure
is too low ） the evaporator temperatu re sensor fault
3 ． A/C relay line fault （ short circuit to ground 、 short circuit to power 、 open
circuit ）
Common troubles ：
Figure9-1 9 A/C relay
To power To m ain relay
Front engine com partment box
Fuel pump
To main relay To main pow er
Electromagnetic clutch
A /C compres sor
20
A/C relay