Simplified Troubleshooting of the Alfa Romeo 164 Cooling Fan System
Background: This simple system seems to be one of the hardest to understand and one of the most confounding and troublesome for the 164 owner to troubleshoot and repair.
I hope this paper will finally keep it simpler.
Wiring diagram info for 91- 95 USA and Canadian models attached in pdf file. Euro models differ slightly.
It is really a simple system to troubleshoot. I suggest you print off the 4 pages I put in pdf file.
Fan motor side of system is HOT AT ALL TIMES via 12v battery power through 40A fuse bar on front of false firewall.
The control system is ONLY HOT WITH KEY ON via F14 fuse in main fuse box under dash. All the control system does is power the energizing side of fan relays and then ground the fan motor relays by either the radiator thermal switch or the A/C trinary pressure switch when either coolant temperature or Freon pressure makes switch click onto ground relays.
TESTING THE WHOLE SYSTEM (key on)
The easiest way to test whole system without any formal test equipment with just a paper clip is to access radiator thermal switch wiring connector(s) next to headlight in front of air cleaner. Remove black plastic cover between headlight and A/C condenser in front of radiator. Disconnect two connectors to thermal switch. If factory thermal switch still installed red wire goes to brown-white wire and is high speed and white wire goes to brown wire and is low speed.
TURN on Key then, using paper clip wire jumper single brown-white wire to black wire in two wire connector or ground to chassis. If F14 fuse in fuse box and the G254 40A fuse bar on false firewall is good, the system working fan will run on high speed or at least relay should click. Now, jumper the brown and black wires in 2-wire connector together with paper clip. Fan should now run on low speed if resistor in fan shroud good or at least relay should click.
If system not passing this test and both fuses F14 and G254 are good test the fan motor circuit next.
If fan runs on high speed only then resistor in fan shroud or wiring to it may be bad if relay clicks.
TESTING JUST THE FAN MOTOR (key off)
The 40A fuse bar G254 must be good to supply 12v HOT AT ALL TIMES) to fan motor. Note: the 40A fuse bar can have a hair line crack in it and look good.
The easiest way is test motor circuit is to remove MIDDLE black cooling fan relays cover on top radiator support. It is the cover between the one for engine ECU red/stripe and fuel pump NON-red stripe relays and the fuses ones for headlight, horn; A/T cooler fan relays.
You need a proper size/gauge wire jumper with two spade connectors to safely do this test this way (at least 2.5mm/12awg size wire).
Now remove both low speed and high speed 50A relays from sockets. Now jumper pin socket 30 in MIDDLE of socket (looks like long leg of letter I pointing towards rear of car) with forward pin socket 87 (top socket of two that looks like = sign closet to front of car). Test each relay socket same way. Fan has to run on high with one relay socket and low with other one if resistor working.
If fan will not work with either relay sockets 30 to 87 jumpered verify 40A fuse has 12v in and out.
Then to test wiring to and from fan motor locate pin 87 (top socket of = sign again and test for 12v with meter red lead to socket 87 and black lead to ground. If no voltage then either motor is bad or more likely bad connection of 2-wire red and brown connector at motor. Repair and test again.
If the resistor or wiring is bad, repair the wiring and/or replace resistor. If you bypass resistor and jumper 2.5 blue and brown wires together fan will run on higher speed but wiring will get hot because wire not full size like high speed side.
Hope this write up helps.
Now as for the A/C system, the Q20 trinary switch on A/C receiver dryer on top of evaporator box behind false firewall by upper engine mount chassis attach point will turn on cooling fan on low speed if fan resistor is good when freon pressure rises to 215 psi and turn it back off about 150 psi. It grounds relay the same way with same colr wires as low temp switch does in radiator.
Background: This simple system seems to be one of the hardest to understand and one of the most confounding and troublesome for the 164 owner to troubleshoot and repair.
I hope this paper will finally keep it simpler.
Wiring diagram info for 91- 95 USA and Canadian models attached in pdf file. Euro models differ slightly.
It is really a simple system to troubleshoot. I suggest you print off the 4 pages I put in pdf file.
Fan motor side of system is HOT AT ALL TIMES via 12v battery power through 40A fuse bar on front of false firewall.
The control system is ONLY HOT WITH KEY ON via F14 fuse in main fuse box under dash. All the control system does is power the energizing side of fan relays and then ground the fan motor relays by either the radiator thermal switch or the A/C trinary pressure switch when either coolant temperature or Freon pressure makes switch click onto ground relays.
TESTING THE WHOLE SYSTEM (key on)
The easiest way to test whole system without any formal test equipment with just a paper clip is to access radiator thermal switch wiring connector(s) next to headlight in front of air cleaner. Remove black plastic cover between headlight and A/C condenser in front of radiator. Disconnect two connectors to thermal switch. If factory thermal switch still installed red wire goes to brown-white wire and is high speed and white wire goes to brown wire and is low speed.
TURN on Key then, using paper clip wire jumper single brown-white wire to black wire in two wire connector or ground to chassis. If F14 fuse in fuse box and the G254 40A fuse bar on false firewall is good, the system working fan will run on high speed or at least relay should click. Now, jumper the brown and black wires in 2-wire connector together with paper clip. Fan should now run on low speed if resistor in fan shroud good or at least relay should click.
If system not passing this test and both fuses F14 and G254 are good test the fan motor circuit next.
If fan runs on high speed only then resistor in fan shroud or wiring to it may be bad if relay clicks.
TESTING JUST THE FAN MOTOR (key off)
The 40A fuse bar G254 must be good to supply 12v HOT AT ALL TIMES) to fan motor. Note: the 40A fuse bar can have a hair line crack in it and look good.
The easiest way is test motor circuit is to remove MIDDLE black cooling fan relays cover on top radiator support. It is the cover between the one for engine ECU red/stripe and fuel pump NON-red stripe relays and the fuses ones for headlight, horn; A/T cooler fan relays.
You need a proper size/gauge wire jumper with two spade connectors to safely do this test this way (at least 2.5mm/12awg size wire).
Now remove both low speed and high speed 50A relays from sockets. Now jumper pin socket 30 in MIDDLE of socket (looks like long leg of letter I pointing towards rear of car) with forward pin socket 87 (top socket of two that looks like = sign closet to front of car). Test each relay socket same way. Fan has to run on high with one relay socket and low with other one if resistor working.
If fan will not work with either relay sockets 30 to 87 jumpered verify 40A fuse has 12v in and out.
Then to test wiring to and from fan motor locate pin 87 (top socket of = sign again and test for 12v with meter red lead to socket 87 and black lead to ground. If no voltage then either motor is bad or more likely bad connection of 2-wire red and brown connector at motor. Repair and test again.
If the resistor or wiring is bad, repair the wiring and/or replace resistor. If you bypass resistor and jumper 2.5 blue and brown wires together fan will run on higher speed but wiring will get hot because wire not full size like high speed side.
Hope this write up helps.
Now as for the A/C system, the Q20 trinary switch on A/C receiver dryer on top of evaporator box behind false firewall by upper engine mount chassis attach point will turn on cooling fan on low speed if fan resistor is good when freon pressure rises to 215 psi and turn it back off about 150 psi. It grounds relay the same way with same colr wires as low temp switch does in radiator.
