1985 12A #2 Temperature Switch function
05-02-23, 09:28 AM
#1
Junior Member
Thread Starter
1985 12A #2 Temperature Switch function
I am trying to diagnose my poorly running 12A. I recently upgraded to an aluminum radiator and dual electric fans. The new radiator does not have a bung for either the coolant level sensor or #2 Temperature Switch. I don't think this temperature switch is at all related because it did run ok for a short while after swapping in this radiator but I'm trying to chase down all possible issues. For the life of me I can't figure out what this temperature switch does based on the FSM wiring.
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Seniorchief (05-19-23)
05-21-23, 09:14 AM
#4
84SE-EGI helpy-helperton
He's talking about the No 2 Water Temp Switch located on the Water pump: you're talking about the Overheat Sensor near the cats under the passenger side carpet.
The water temp switches are used to signal the ECU as to when the coolant is hot or cold which is used by the ECU to set Choke hold and other idle co sensation controls. If the Water Temp Switch goes out, typically you'll get high idle, poor exhaust emissions, and an overly rich mixture, because the ECU thinks the coolant is cold all the time and never turns off cold start systems.
There are 2 Water Temp switches, obviously - one on the back of the Water Pump and another on the block, at least on the 84SE model. Follow your wiring diagram to locate them. The block mounted water temp switch is used as a differential reference between the block temp and coolant temp, and are simple On/Off registers.
For a solution to aluminum radiators which lack a threaded bung for your coolant level sensor, search here on my username and "aftermarket aluminum radiator".
The water temp switches are used to signal the ECU as to when the coolant is hot or cold which is used by the ECU to set Choke hold and other idle co sensation controls. If the Water Temp Switch goes out, typically you'll get high idle, poor exhaust emissions, and an overly rich mixture, because the ECU thinks the coolant is cold all the time and never turns off cold start systems.
There are 2 Water Temp switches, obviously - one on the back of the Water Pump and another on the block, at least on the 84SE model. Follow your wiring diagram to locate them. The block mounted water temp switch is used as a differential reference between the block temp and coolant temp, and are simple On/Off registers.
For a solution to aluminum radiators which lack a threaded bung for your coolant level sensor, search here on my username and "aftermarket aluminum radiator".
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diabolical1 (05-23-23)
05-24-23, 09:16 AM
#5
Junior Member
Thread Starter
He's talking about the No 2 Water Temp Switch located on the Water pump: you're talking about the Overheat Sensor near the cats under the passenger side carpet.
The water temp switches are used to signal the ECU as to when the coolant is hot or cold which is used by the ECU to set Choke hold and other idle co sensation controls. If the Water Temp Switch goes out, typically you'll get high idle, poor exhaust emissions, and an overly rich mixture, because the ECU thinks the coolant is cold all the time and never turns off cold start systems.
There are 2 Water Temp switches, obviously - one on the back of the Water Pump and another on the block, at least on the 84SE model. Follow your wiring diagram to locate them. The block mounted water temp switch is used as a differential reference between the block temp and coolant temp, and are simple On/Off registers.
For a solution to aluminum radiators which lack a threaded bung for your coolant level sensor, search here on my username and "aftermarket aluminum radiator".
The water temp switches are used to signal the ECU as to when the coolant is hot or cold which is used by the ECU to set Choke hold and other idle co sensation controls. If the Water Temp Switch goes out, typically you'll get high idle, poor exhaust emissions, and an overly rich mixture, because the ECU thinks the coolant is cold all the time and never turns off cold start systems.
There are 2 Water Temp switches, obviously - one on the back of the Water Pump and another on the block, at least on the 84SE model. Follow your wiring diagram to locate them. The block mounted water temp switch is used as a differential reference between the block temp and coolant temp, and are simple On/Off registers.
For a solution to aluminum radiators which lack a threaded bung for your coolant level sensor, search here on my username and "aftermarket aluminum radiator".
05-24-23, 09:49 AM
#6
Junior Member
Thread Starter
Found my answer while looking for info on aftermarket aluminum radiators:
https://www.rx7club.com/new-member-r...t-out-1153401/
TL;DR: It has to do with the smog pump/emissions which I no longer have so no need to bother with this sensor.
https://www.rx7club.com/new-member-r...t-out-1153401/
TL;DR: It has to do with the smog pump/emissions which I no longer have so no need to bother with this sensor.
05-24-23, 09:50 AM
#7
To test if this NO.2 switch is the issue, put it in a cup of ice water and see how it runs. You could also use a lighter and apply some heat to test. No sure what the threshold for this switch/sensor is but the factory service manual generally has some good test procedures.
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05-24-23, 09:54 AM
#8
Junior Member
Thread Starter
Wish I could test the switch but it basically crumbled to bits upon removal from the old radiator. Per the link I just posted above, sounds like it only impacts the air injection pump which I no longer have. I'll try to jumper/un-jumper the connector though at start up and see if there's any impact just to be 100% sure.
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