jeepster
Active Member
I had the engine changed, now the radiator fan's not working.
Only if airconditioner is on: fan will start about half a second
after the compressor clutch and turn off 5 seconds after the
clutch.
Otherwise, running the engine with car in park, the temperature
rises and rises. The overflow tank starts bubbling at about 60% on the
temperature guage, but no fan. With old engine, the fan came
on before 50% on the guage (without aircon).
I checked the temperature guage with resistors - 39 ohms sends
the needle to H, and 62 ohms to midway, so it is working.
Next inspected the wiring for damage. I pulled the panels
out to get at PCM, all the connectors were firmly in place.
I swapped the fan relays, no effect.
I shorted out the contacts which are the relay normally
open pins, and the fans run. However low and high speed
sounded very similar.
I unplugged the coolant sensor, and started the engine:
low-speed then high-speed fan. A faulty sensor should turn on the
fan as failsafe. I should have tried this first.
I shorted contacts 5 and 6 of the PCM diagnostic connector: fan
did not run. I read somewhere that fan should start in diagnostic
mode. I got no PCM error codes, just 12.
I connected 180 ohm resistor across the sensor plug: fan off.
I connected 150 ohm resistor - this gave me low-speed fan.
Connecting 100 to 130 ohms: low speed for 5 seconds, then
high speed.
The last test suggests that the fuses, relays and PCM are
okay and the coolant sensor is bad. I could not get probes
of a multimeter on the sensor contacts, so I just bought a new
unit for $62. I put it in, topped up the coolant, and bled the
air. I ran the engine until the overflow tank was boiling, but
the fan still does not come on. The radiator cap is correct
pressure rating, and is 5 months old.
I was puzzled - is the new sensor bad?
I put the old sensor in boiling water and measured it, I got
181 ohms, which means the old sensor was near enough to good
and should have triggered the fan.
Any ideas?
Only if airconditioner is on: fan will start about half a second
after the compressor clutch and turn off 5 seconds after the
clutch.
Otherwise, running the engine with car in park, the temperature
rises and rises. The overflow tank starts bubbling at about 60% on the
temperature guage, but no fan. With old engine, the fan came
on before 50% on the guage (without aircon).
I checked the temperature guage with resistors - 39 ohms sends
the needle to H, and 62 ohms to midway, so it is working.
Next inspected the wiring for damage. I pulled the panels
out to get at PCM, all the connectors were firmly in place.
I swapped the fan relays, no effect.
I shorted out the contacts which are the relay normally
open pins, and the fans run. However low and high speed
sounded very similar.
I unplugged the coolant sensor, and started the engine:
low-speed then high-speed fan. A faulty sensor should turn on the
fan as failsafe. I should have tried this first.
I shorted contacts 5 and 6 of the PCM diagnostic connector: fan
did not run. I read somewhere that fan should start in diagnostic
mode. I got no PCM error codes, just 12.
I connected 180 ohm resistor across the sensor plug: fan off.
I connected 150 ohm resistor - this gave me low-speed fan.
Connecting 100 to 130 ohms: low speed for 5 seconds, then
high speed.
The last test suggests that the fuses, relays and PCM are
okay and the coolant sensor is bad. I could not get probes
of a multimeter on the sensor contacts, so I just bought a new
unit for $62. I put it in, topped up the coolant, and bled the
air. I ran the engine until the overflow tank was boiling, but
the fan still does not come on. The radiator cap is correct
pressure rating, and is 5 months old.
I was puzzled - is the new sensor bad?
I put the old sensor in boiling water and measured it, I got
181 ohms, which means the old sensor was near enough to good
and should have triggered the fan.
Any ideas?