Need Help Please "Coolant temp sensor"
07-25-2002, 06:58 PM
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Need Help Please "Coolant temp sensor"
I need help.
Every time I connect the Coolant temperature sensor "which attaches in the thermostat housing" my 928 '82 turns off. Before this my car would not turn on at all. I disconnected the Coolant temperature switch and the car started again. I just recently replaced it with a new one. Guess what happened? There is no change. Could it be a short in the connecting wires?
New porsche owner...
1982 928
Every time I connect the Coolant temperature sensor "which attaches in the thermostat housing" my 928 '82 turns off. Before this my car would not turn on at all. I disconnected the Coolant temperature switch and the car started again. I just recently replaced it with a new one. Guess what happened? There is no change. Could it be a short in the connecting wires?
New porsche owner...
1982 928
07-29-2002, 12:11 PM
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Iacast,
Check the lead to the sensor (ign on) and see if it has +12V on it. It should have some volts on it. Does the sensor have one contact pin, or 2? Which injection is your car - CIS, L or LH - 82 US I would guess L-jet. I have seen a report that some sensors have a pin for temp gauge and another for 'too hot' red light - ???
What does your car do if you short the lead to earth (engine metal)? Does the temp gauge read at all, engine running or not, lead connected or not? Does the gauge read if you short the lead to engine earth?
Check resistance between lead end (not connected ) and earth - should be some if it is going through a gauge. If near zero, sounds like shorted, but still dont know whay that would stop engine, unless shorted with something critical. I suggest you locate the fuse board connection for the lead, and test that it gets there without being grounded anywhere along the way. You may need some sort of cable tracing tool to help here, BTDT.
jp
Check the lead to the sensor (ign on) and see if it has +12V on it. It should have some volts on it. Does the sensor have one contact pin, or 2? Which injection is your car - CIS, L or LH - 82 US I would guess L-jet. I have seen a report that some sensors have a pin for temp gauge and another for 'too hot' red light - ???
What does your car do if you short the lead to earth (engine metal)? Does the temp gauge read at all, engine running or not, lead connected or not? Does the gauge read if you short the lead to engine earth?
Check resistance between lead end (not connected ) and earth - should be some if it is going through a gauge. If near zero, sounds like shorted, but still dont know whay that would stop engine, unless shorted with something critical. I suggest you locate the fuse board connection for the lead, and test that it gets there without being grounded anywhere along the way. You may need some sort of cable tracing tool to help here, BTDT.
jp
07-29-2002, 02:33 PM
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On the '82 ...
The coolant temp sending unit has two outputs - the blue/yellow wire attached to "G" operates the temp gauge; the blue/green wire attached to "W" operates the overheat warning light. I know of no way that either of these could kill the engine.
The thermotime switch for the cold start valve has a brown/yellow wire attached to "G" and two yellow wires attached to "W". If the switch is shorted, it will activate the cold start valve, resulting in a very rich mixture, killing a warm engine.
Measuring from the terminals to ground, below 86 deg F there should be 0 Ohms; above 104 deg F there should be 100-160 Ohms.
Measuring between the terminals, below 86 deg F there should be 25-40 Ohms; above 104 deg F there should be 50-80 Ohms.
The injection temp sensor (Temp Sensor II) has a gray plug and a single yellow wire attached. If the sensor is bad, it could result in a very rich mixture, killing a warm engine. At 68 deg F there should be 2-3 kOhms to ground, at 176 deg F there should be 250-300 Ohms to ground.
The coolant temp sending unit has two outputs - the blue/yellow wire attached to "G" operates the temp gauge; the blue/green wire attached to "W" operates the overheat warning light. I know of no way that either of these could kill the engine.
The thermotime switch for the cold start valve has a brown/yellow wire attached to "G" and two yellow wires attached to "W". If the switch is shorted, it will activate the cold start valve, resulting in a very rich mixture, killing a warm engine.
Measuring from the terminals to ground, below 86 deg F there should be 0 Ohms; above 104 deg F there should be 100-160 Ohms.
Measuring between the terminals, below 86 deg F there should be 25-40 Ohms; above 104 deg F there should be 50-80 Ohms.
The injection temp sensor (Temp Sensor II) has a gray plug and a single yellow wire attached. If the sensor is bad, it could result in a very rich mixture, killing a warm engine. At 68 deg F there should be 2-3 kOhms to ground, at 176 deg F there should be 250-300 Ohms to ground.
