Testing for the engine fan system
Thread Starter
Intermediate
Joined: Sep 2021
Posts: 39
Likes: 14
Testing for the engine fan system
1988 coupe
I'm making another attempt at doing some testing prior to hardwiring a switch to the engine fan.
The wiring and various parts, as I understand them, consists of the following:
A sensor attached to the engine block by cylinder 8.
A single wire routing from the sensor into the cabin and into the ECM.
I am only aware of one wire leading into the ECM - and that is in pin/plug C1. I need to verify the color.
a green/white wire then leads from the ECM to the cooling fan relay. I'm not certain if that is the wire from C1, but will do a continuity test.
If I recall correctly, the last time I measured pin F, it was slightly higher than at 0Vdc. Something like 0.3Vdc.
Today I am going to try and check the wire leading from the sensor to the ECM. I'll also take out the sensor and make sure it has a good connection to the engine block
Info from 65Z01:
The aux fan switch near #1 spark plug only controls the booster fan via the aux fan relay on the left top of the radiator shroud. This sensor does NOT control the main coolant fan, only the ECM controls the main coolant fan.
The main coolant fan relay is located on the rear of the left fender well, below the master cylinder. Wires to this relay are:
-at pin F a Grn/Wht wire from ECM pin C1,
-at pin E a large Red wire from Fusable Link D,
-at pin D a Dk Blu wire from the C. Fan Fuse,
-at pin A a Blk/Red wire to the Coolant Fan Motor.
Once you have the main coolant fan relay wired up properly simply jumper ALDL pins A&B (upper right), turn on the ignition and the main coolant fan should come on.
If not, verify that pin F is at 0Vdc.
If not, ring out the Grn/Wht wire to the ECM.
If so, verify that +12Vdc is present on the Red wire at pin E.
If not, trace power through the Fusable link and the connector.
If so, verify that +12Vdc is present on the Dk Blu wire with ignition On.
If not, check the C. Fan Fuse.
If so, verify that +12Vdc is present on the Blk/Red wire at pin A with the ALDL jumper in place and ignition On.
If not, replace the relay.
If so, pull the relay and jump +12Vdc to the Blk/Red wire pin to see if the main coolant fan comes on.
If not, repeat the jumper at the fan.
If so, trace the Blk/Red wire for an open.
If still not, replace the fan.
I'm making another attempt at doing some testing prior to hardwiring a switch to the engine fan.
The wiring and various parts, as I understand them, consists of the following:
A sensor attached to the engine block by cylinder 8.
A single wire routing from the sensor into the cabin and into the ECM.
I am only aware of one wire leading into the ECM - and that is in pin/plug C1. I need to verify the color.
a green/white wire then leads from the ECM to the cooling fan relay. I'm not certain if that is the wire from C1, but will do a continuity test.
If I recall correctly, the last time I measured pin F, it was slightly higher than at 0Vdc. Something like 0.3Vdc.
Today I am going to try and check the wire leading from the sensor to the ECM. I'll also take out the sensor and make sure it has a good connection to the engine block
Info from 65Z01:
The aux fan switch near #1 spark plug only controls the booster fan via the aux fan relay on the left top of the radiator shroud. This sensor does NOT control the main coolant fan, only the ECM controls the main coolant fan.
The main coolant fan relay is located on the rear of the left fender well, below the master cylinder. Wires to this relay are:
-at pin F a Grn/Wht wire from ECM pin C1,
-at pin E a large Red wire from Fusable Link D,
-at pin D a Dk Blu wire from the C. Fan Fuse,
-at pin A a Blk/Red wire to the Coolant Fan Motor.
Once you have the main coolant fan relay wired up properly simply jumper ALDL pins A&B (upper right), turn on the ignition and the main coolant fan should come on.
If not, verify that pin F is at 0Vdc.
If not, ring out the Grn/Wht wire to the ECM.
If so, verify that +12Vdc is present on the Red wire at pin E.
If not, trace power through the Fusable link and the connector.
If so, verify that +12Vdc is present on the Dk Blu wire with ignition On.
If not, check the C. Fan Fuse.
If so, verify that +12Vdc is present on the Blk/Red wire at pin A with the ALDL jumper in place and ignition On.
If not, replace the relay.
If so, pull the relay and jump +12Vdc to the Blk/Red wire pin to see if the main coolant fan comes on.
If not, repeat the jumper at the fan.
If so, trace the Blk/Red wire for an open.
If still not, replace the fan.
Drifting
Joined: Jan 2021
Posts: 1,312
Likes: 383
From: Northern California
(I have no idea on how this affects or doesn't affect your proposed cooling fan switch mod, I'm just correcting the part about what those sensors do and where they are located)
1988 coupe
I'm making another attempt at doing some testing prior to hardwiring a switch to the engine fan.
The wiring and various parts, as I understand them, consists of the following:
A sensor attached to the engine block by cylinder 8. (Nope, that's for the dash gauge cluster temperature display reading. The Coolant Temperature Sensor (CTS) which feeds information to the ECM is in the front of the intake manifold underneath the throttle body area.)
A single wire routing from the sensor into the cabin and into the ECM. (The CTS above is a two-wire connector back into the main harness to the ECM; I haven't looked at the schematic but one of those may be a ground wire and the other is signal to ECM. Either way, that CTS has two wires from it.)
I am only aware of one wire leading into the ECM - and that is in pin/plug C1. I need to verify the color.
a green/white wire then leads from the ECM to the cooling fan relay. I'm not certain if that is the wire from C1, but will do a continuity test.
If I recall correctly, the last time I measured pin F, it was slightly higher than at 0Vdc. Something like 0.3Vdc.
Today I am going to try and check the wire leading from the sensor to the ECM. I'll also take out the sensor and make sure it has a good connection to the engine block
1988 coupe
I'm making another attempt at doing some testing prior to hardwiring a switch to the engine fan.
The wiring and various parts, as I understand them, consists of the following:
I am only aware of one wire leading into the ECM - and that is in pin/plug C1. I need to verify the color.
a green/white wire then leads from the ECM to the cooling fan relay. I'm not certain if that is the wire from C1, but will do a continuity test.
If I recall correctly, the last time I measured pin F, it was slightly higher than at 0Vdc. Something like 0.3Vdc.
Today I am going to try and check the wire leading from the sensor to the ECM. I'll also take out the sensor and make sure it has a good connection to the engine block
Last edited by ajp01; Oct 25, 2021 at 05:52 PM. Reason: quote fix
Thread Starter
Intermediate
Joined: Sep 2021
Posts: 39
Likes: 14
(I have no idea on how this affects or doesn't affect your proposed cooling fan switch mod, I'm just correcting the part about what those sensors do and where they are located)
1988 coupe
I'm making another attempt at doing some testing prior to hardwiring a switch to the engine fan.
The wiring and various parts, as I understand them, consists of the following:
A sensor attached to the engine block by cylinder 8. (Nope, that's for the dash gauge cluster temperature display reading. The Coolant Temperature Sensor (CTS) which feeds information to the ECM is in the front of the intake manifold underneath the throttle body area.)
A single wire routing from the sensor into the cabin and into the ECM. (The CTS above is a two-wire connector back into the main harness to the ECM; I haven't looked at the schematic but one of those may be a ground wire and the other is signal to ECM. Either way, that CTS has two wires from it.)
I am only aware of one wire leading into the ECM - and that is in pin/plug C1. I need to verify the color.
a green/white wire then leads from the ECM to the cooling fan relay. I'm not certain if that is the wire from C1, but will do a continuity test.
If I recall correctly, the last time I measured pin F, it was slightly higher than at 0Vdc. Something like 0.3Vdc.
Today I am going to try and check the wire leading from the sensor to the ECM. I'll also take out the sensor and make sure it has a good connection to the engine block
1988 coupe
I'm making another attempt at doing some testing prior to hardwiring a switch to the engine fan.
The wiring and various parts, as I understand them, consists of the following:
I am only aware of one wire leading into the ECM - and that is in pin/plug C1. I need to verify the color.
a green/white wire then leads from the ECM to the cooling fan relay. I'm not certain if that is the wire from C1, but will do a continuity test.
If I recall correctly, the last time I measured pin F, it was slightly higher than at 0Vdc. Something like 0.3Vdc.
Today I am going to try and check the wire leading from the sensor to the ECM. I'll also take out the sensor and make sure it has a good connection to the engine block
Team Owner
Joined: Sep 2003
Posts: 25,386
Likes: 2,740
ECM from CTS is C10 'YELLOW' Cir 410
In an older post you mention ECM issues and posted snapshot with some issues.
Assuming you don't have the AUX FAN why wouldn't you consider using a Temp Sensor Control in left cylinder head between 1 & 3? Add to that if you like the 'manual control switch'! There are various switches for open/close temp control.
If you've issues with CTS & ECM you've likely more critical issues to be concerned with other than FAN control.
What/how does the information by '65Z01' relate at all? If you've the FSM all info you need is there. 6E3-A-1 through 7 for ECM info.
In an older post you mention ECM issues and posted snapshot with some issues.
Assuming you don't have the AUX FAN why wouldn't you consider using a Temp Sensor Control in left cylinder head between 1 & 3? Add to that if you like the 'manual control switch'! There are various switches for open/close temp control.
If you've issues with CTS & ECM you've likely more critical issues to be concerned with other than FAN control.
What/how does the information by '65Z01' relate at all? If you've the FSM all info you need is there. 6E3-A-1 through 7 for ECM info.
Last edited by WVZR-1; Oct 26, 2021 at 09:26 AM.
Thread Starter
Intermediate
Joined: Sep 2021
Posts: 39
Likes: 14
ECM from CTS is C10 'YELLOW' Cir 410
In an older post you mention ECM issues and posted snapshot with some issues.
Assuming you don't have the AUX FAN why wouldn't you consider using a Temp Sensor Control in left cylinder head between 1 & 3? Add to that if you like the 'manual control switch'! There are various switches for open/close temp control.
If you've issues with CTS & ECM you've likely more critical issues to be concerned with other than FAN control.
In an older post you mention ECM issues and posted snapshot with some issues.
Assuming you don't have the AUX FAN why wouldn't you consider using a Temp Sensor Control in left cylinder head between 1 & 3? Add to that if you like the 'manual control switch'! There are various switches for open/close temp control.
If you've issues with CTS & ECM you've likely more critical issues to be concerned with other than FAN control.
Thanks again - comments like this are gold for those of us new to the car.
Team Owner
Joined: Sep 2003
Posts: 25,386
Likes: 2,740
You need to spend more time in the 6E3-A section of the FSM. It would be very interesting to maybe search 'locally' for some one with an appropriate scanner to confirm your issues. Having the ECM issues mentioned in other post a scan would be maybe a 'tell-all'!
Where are you located?
Where are you located?
Thread Starter
Intermediate
Joined: Sep 2021
Posts: 39
Likes: 14
You need to spend more time in the 6E3-A section of the FSM. It would be very interesting to maybe search 'locally' for some one with an appropriate scanner to confirm your issues. Having the ECM issues mentioned in other post a scan would be maybe a 'tell-all'!
Where are you located?
Where are you located?
Team Owner
Joined: Sep 2003
Posts: 25,386
Likes: 2,740
Post in this section mention looking for Tech1 or Tech1a OR similar scanner in your area to buy rent or 'HIRE'!!
Someone might mention a shop or maybe offer use of!!
https://www.corvetteforum.com/forums...in-prairie-46/
I'll have one available for sale likely soon but not right now!
Last edited by WVZR-1; Oct 27, 2021 at 09:49 AM.
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