New owner weeding out the problems
01-13-2002, 02:18 PM
#1
Racer
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New owner weeding out the problems
Hello All,
I have bought a 87' 928S4 U.S., automatic and I'm trying to solve a overheating problem, the electric radiator fan is not coming on when the temp. rises up into the no no zone, when I energize the a/c both fans come on as they should and the temp. drops to normal, also when the car is moving the temp. is ok. I don't have a manual set for the car yet so any help will be greatly appreciated.
I have bought a 87' 928S4 U.S., automatic and I'm trying to solve a overheating problem, the electric radiator fan is not coming on when the temp. rises up into the no no zone, when I energize the a/c both fans come on as they should and the temp. drops to normal, also when the car is moving the temp. is ok. I don't have a manual set for the car yet so any help will be greatly appreciated.
01-13-2002, 02:26 PM
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Welcome!
Give this a shot while you're waiting for the gurus here to contribute.
The on-line bible of collected 928 wisdom is at:
Nichols page
There's an entire section on engine cooling there.
Good luck.
Give this a shot while you're waiting for the gurus here to contribute.
The on-line bible of collected 928 wisdom is at:
Nichols page
There's an entire section on engine cooling there.
Good luck.
01-13-2002, 04:05 PM
#3
Erik,
It appears you fan temp switch is bad. Not sure where it is located on your model, but mine is located on the drivers side, front bottom of the radiator.
Dennis
It appears you fan temp switch is bad. Not sure where it is located on your model, but mine is located on the drivers side, front bottom of the radiator.
Dennis
01-13-2002, 04:10 PM
#4
Three Wheelin'
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Eric,
First check fuses and relays. Next check the fan motor, feed 12V and ground to the disconnected fan wires. If the fan does not come on the motor is bad. If the fan comes on, jump the fan switch plug, two wires driver’s side front of the radiator, lower corner. If the fan does not come, there are two output stage modules for fan control, not an easy fix.
When the ac fan is on are the front flaps open all the way?
SteveC
The Great White
First check fuses and relays. Next check the fan motor, feed 12V and ground to the disconnected fan wires. If the fan does not come on the motor is bad. If the fan comes on, jump the fan switch plug, two wires driver’s side front of the radiator, lower corner. If the fan does not come, there are two output stage modules for fan control, not an easy fix.
When the ac fan is on are the front flaps open all the way?
SteveC
The Great White
01-14-2002, 12:03 AM
#5
Racer
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Thanks for the help,
I found what I think is the temp. senser in the lower left front of the radiator, the connector has two wires a blue with a green stripe and a brown with a black stripe. I don't want to jump out the circuit until I'm sure this is the right connector and that the wires are to be jumped together or jumped to ground (most of these type switches I've checked in the past have been grounding type.
Steve, the front flaps do open when the a/c is switched on and both fans run.
I found what I think is the temp. senser in the lower left front of the radiator, the connector has two wires a blue with a green stripe and a brown with a black stripe. I don't want to jump out the circuit until I'm sure this is the right connector and that the wires are to be jumped together or jumped to ground (most of these type switches I've checked in the past have been grounding type.
Steve, the front flaps do open when the a/c is switched on and both fans run.
01-14-2002, 04:02 PM
#6
Chronic Tool Dropper
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Eric:
Welcome to the 928!
Fans operate on a remp signal from a temp transducer rather than a switch on the S4+ cars. A sender if you will. Temp profile determines the fan speed, as does hi-side pressure in the AC system. If the fans run with the AC as you indicate, your fans and the FET speed module (thick black heatsink fins on the pass side apron under the front edge of the hood) are fine. I don't remember exactly where on the radiator the sender is for fan control, but definitely not a good idea to short it out or 'jumper' the wires.
Simple test before you get too deep: Is there circulation through the radiator? The 928 has a thermostat that manages flow through the radiator by blocking coolant flow through a recirculation passage in the block. So in addition to any "normal" thermostat function you might expect blocking flow to the radiator when cold, it also needs to block the recirc flow when warm. If you PO decided that a cure for a heating problem is thermostat removal, overheating is inevitable. Easy hands-on test for coolant circulation is heat in the lower (that's the one on the right as you face the front of the car...) hose when the engine is started and warms up.
This of course all assumes that you've done the basic stuff like make sure there is actually coolant in the car... Worth checking.
Hope this helps!
Welcome to the 928!
Fans operate on a remp signal from a temp transducer rather than a switch on the S4+ cars. A sender if you will. Temp profile determines the fan speed, as does hi-side pressure in the AC system. If the fans run with the AC as you indicate, your fans and the FET speed module (thick black heatsink fins on the pass side apron under the front edge of the hood) are fine. I don't remember exactly where on the radiator the sender is for fan control, but definitely not a good idea to short it out or 'jumper' the wires.
Simple test before you get too deep: Is there circulation through the radiator? The 928 has a thermostat that manages flow through the radiator by blocking coolant flow through a recirculation passage in the block. So in addition to any "normal" thermostat function you might expect blocking flow to the radiator when cold, it also needs to block the recirc flow when warm. If you PO decided that a cure for a heating problem is thermostat removal, overheating is inevitable. Easy hands-on test for coolant circulation is heat in the lower (that's the one on the right as you face the front of the car...) hose when the engine is started and warms up.
This of course all assumes that you've done the basic stuff like make sure there is actually coolant in the car... Worth checking.
Hope this helps!
01-15-2002, 10:41 PM
#7
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Eric,
The coolant temperature sender for the fan is a thermo switch. It has a negative temperature coefficient (NTC). Just like any temperature switch. This is a fancy name for a resistor whose resistance decreases when temperature increases. What that means is when the coolant is 60 degrees C; the sensor will have a resistance of 3862 Ohm’s (cold engine). At 100 degrees C, the switch will have a resistance of 967 Ohm’s (hot engine).
I can understand your concern with jumping the sensor. Go to radio shack and buy a 967 Ohm resistor, install it in series with the wires from the temp sensor. This will simulate a hot engine. If the fan goes on you have a bad switch.
Good Luck,
Steve C
The Great White
The coolant temperature sender for the fan is a thermo switch. It has a negative temperature coefficient (NTC). Just like any temperature switch. This is a fancy name for a resistor whose resistance decreases when temperature increases. What that means is when the coolant is 60 degrees C; the sensor will have a resistance of 3862 Ohm’s (cold engine). At 100 degrees C, the switch will have a resistance of 967 Ohm’s (hot engine).
I can understand your concern with jumping the sensor. Go to radio shack and buy a 967 Ohm resistor, install it in series with the wires from the temp sensor. This will simulate a hot engine. If the fan goes on you have a bad switch.
Good Luck,
Steve C
The Great White