What Pin to Add Ground on relay to Make Rad Fans run
Rolm
10-04-2012, 04:06 PM
Can anyone tell me what pin to add a ground on Rad Fan relay no.1 to make the Rad fans run at low speed.
Rolm
10-04-2012, 06:13 PM
Ok i found the pin where to place the ground and yes the fans do run in a slow speed. Now I need a switched ground so when I turn off the car the fans stop.
Rolm
10-08-2012, 12:43 PM
Ok I can control the temp by placing a ground and the fans run at low speed which I want and the temp stays 3/4 of the way before the mid point on the temp gauge which is perfect. When I do this I get an engine lite come on with an error code of fan 1 is defective. I guess the choice here is do I keep the fans running and keep the engine cool with the engine light on or turn off the fans over-heat the engine with no engine light on. I think I will keep the fans running till I find a permanent fix.
sverker
10-09-2012, 03:34 AM
This is the cooling fan circuit:
46817
Probably the PCM is detecting that you are forcing the signal pin low. You should be able to avoid that by adding a diod in series with the signal from PCM to block the backcurrent and a pull up resistor to keep the signal high.
46817
Probably the PCM is detecting that you are forcing the signal pin low. You should be able to avoid that by adding a diod in series with the signal from PCM to block the backcurrent and a pull up resistor to keep the signal high.
Tech II
10-09-2012, 12:13 PM
Here's the rub.....if the PCM is detecting 0 volts because he has grounded the circuit, and runs the fan, it means the circuit is good to the PCM......I would like to get a Tech II on that car and command the fan on, and check ECT data.....
Rolm
10-19-2012, 07:47 PM
Here's the rub.....if the PCM is detecting 0 volts because he has grounded the circuit, and runs the fan, it means the circuit is good to the PCM......I would like to get a Tech II on that car and command the fan on, and check ECT data.....
I agree with you that is the frustrating part, I was surprised that the PCM detected the ground I was sure it was the ground from the PCM that was missing and that was the cause of the problem.
So now What??
Next question what is a Tech II ???
I agree with you that is the frustrating part, I was surprised that the PCM detected the ground I was sure it was the ground from the PCM that was missing and that was the cause of the problem.
So now What??
Next question what is a Tech II ???
Rolm
10-19-2012, 07:51 PM
This is the cooling fan circuit:
46817
Probably the PCM is detecting that you are forcing the signal pin low. You should be able to avoid that by adding a diod in series with the signal from PCM to block the backcurrent and a pull up resistor to keep the signal high.
Thanks for the suggestion I am not going there.
Do you know where I can get a switched ground if not then I will have to build a set-up with the relay where I will get a switched ground.
If I had the choice of running with a cool engine and an engine light I will choose the engine light been on.
46817
Probably the PCM is detecting that you are forcing the signal pin low. You should be able to avoid that by adding a diod in series with the signal from PCM to block the backcurrent and a pull up resistor to keep the signal high.
Thanks for the suggestion I am not going there.
Do you know where I can get a switched ground if not then I will have to build a set-up with the relay where I will get a switched ground.
If I had the choice of running with a cool engine and an engine light I will choose the engine light been on.
Rolm
10-19-2012, 07:57 PM
Many years ago I had the same problem with my 99 olds and the way I fixed that was by buying a bypass cooling harness that the guys used to cool their engine with the engine off. You just unplugged the the cooling fans and pluged this harness in it's place and you had a switch the allowed you to turn the fans on low or hi high it was a nice set-up. I can't find it on web I did by it off a guy on Kijiji
Tech II
10-19-2012, 10:37 PM
OK, I guess I am the one who has to ask the question: Why are you doing this?
Is it overheating? If you manually run the fan, it doesn't overheat? Have you checked coolant level in the radiator and the reservoir, when the engine is COLD?
There is nothing wrong with the cooling fan circuit, because it runs with the A/C on.......the circuit is controlled by the PCM, for A/C cooling AND for cooling off the engine.....
First off, a Tech II is the scan tool used by GM techs to diagnose vehicles....
When I check a car for a P0128, I take a vehicle at normal operating temp, out on the highway and cruise at 65 and watch ECT data.......being on the highway, with 65mph air going through the radiator fins, no cooling fan is necessary, so it should be off.....Therm should open at 190F, but it could vary a few degrees either way.......when a P0128 is set, you will see the ECT data go very low, maybe 160-170F, and if you drive on the highway for any length of time, the temp will stay in this range, and not reach 190F, and will set P0128.....Also while watching data, you watch the temp gage at the same time, to make sure they read the same.......have seen as much as 5-15F difference due to a bad cluster....
What you are looking for, with a normally operating thermostat, is for the ECT data to cycle from 190-200F, approximately, on the highway.......so when the therm closes, temp will start to rise.....can reach as much as 200F, before it drops back down to 190F, because the therm has opened....have to remember, temps are not instantaneous......it takes awhile for the coolant to flow out of the engine through the radiator and then back to the engine......as it enters the engine it's lower than when it left, but by the time it gets back to the ECT sensor, it has picked up some heat from the engine, so this is a gradual rise and fall we have here.....So if I see this aprox 190-200 cycle on the highway, I know the therm is ok....
Now, you check the cycling of the coolant fan.....You let the car idle in park, and since no air is flowing across the radiator, temp will really start to rise.....I"m guessing your low speed fan comes on at about 218F.......when the fan comes on at 218F, temp can still rise until the cooled, coolant returns to the engine.......but with the fan continuously running, temp will probably drop to about 210, and the fan shuts off.....temp could still drop a few more degrees.......then the temp rises, and we have another repeated cycle of 210-220F(approx)....If you are in heavy traffic, on a hot day, the low speed fan can't handle the the high temp, and if the coolant reaches 228(once again this is a guess on my part), then the PCM commands the fan(s) to high......the temp could actually rise a few degrees more, before the effect of the high speed fan is realized.......when it approaches 218F, the speed could drop to low speed.....
This is about the only way, that the system can be truly checked (especially if the gage is slightly off)......
Is it overheating? If you manually run the fan, it doesn't overheat? Have you checked coolant level in the radiator and the reservoir, when the engine is COLD?
There is nothing wrong with the cooling fan circuit, because it runs with the A/C on.......the circuit is controlled by the PCM, for A/C cooling AND for cooling off the engine.....
First off, a Tech II is the scan tool used by GM techs to diagnose vehicles....
When I check a car for a P0128, I take a vehicle at normal operating temp, out on the highway and cruise at 65 and watch ECT data.......being on the highway, with 65mph air going through the radiator fins, no cooling fan is necessary, so it should be off.....Therm should open at 190F, but it could vary a few degrees either way.......when a P0128 is set, you will see the ECT data go very low, maybe 160-170F, and if you drive on the highway for any length of time, the temp will stay in this range, and not reach 190F, and will set P0128.....Also while watching data, you watch the temp gage at the same time, to make sure they read the same.......have seen as much as 5-15F difference due to a bad cluster....
What you are looking for, with a normally operating thermostat, is for the ECT data to cycle from 190-200F, approximately, on the highway.......so when the therm closes, temp will start to rise.....can reach as much as 200F, before it drops back down to 190F, because the therm has opened....have to remember, temps are not instantaneous......it takes awhile for the coolant to flow out of the engine through the radiator and then back to the engine......as it enters the engine it's lower than when it left, but by the time it gets back to the ECT sensor, it has picked up some heat from the engine, so this is a gradual rise and fall we have here.....So if I see this aprox 190-200 cycle on the highway, I know the therm is ok....
Now, you check the cycling of the coolant fan.....You let the car idle in park, and since no air is flowing across the radiator, temp will really start to rise.....I"m guessing your low speed fan comes on at about 218F.......when the fan comes on at 218F, temp can still rise until the cooled, coolant returns to the engine.......but with the fan continuously running, temp will probably drop to about 210, and the fan shuts off.....temp could still drop a few more degrees.......then the temp rises, and we have another repeated cycle of 210-220F(approx)....If you are in heavy traffic, on a hot day, the low speed fan can't handle the the high temp, and if the coolant reaches 228(once again this is a guess on my part), then the PCM commands the fan(s) to high......the temp could actually rise a few degrees more, before the effect of the high speed fan is realized.......when it approaches 218F, the speed could drop to low speed.....
This is about the only way, that the system can be truly checked (especially if the gage is slightly off)......
Rolm
10-20-2012, 01:12 PM
OK, I guess I am the one who has to ask the question: Why are you doing this?
Is it overheating? If you manually run the fan, it doesn't overheat? Have you checked coolant level in the radiator and the reservoir, when the engine is COLD?
There is nothing wrong with the cooling fan circuit, because it runs with the A/C on.......the circuit is controlled by the PCM, for A/C cooling AND for cooling off the engine.....
First off, a Tech II is the scan tool used by GM techs to diagnose vehicles....
When I check a car for a P0128, I take a vehicle at normal operating temp, out on the highway and cruise at 65 and watch ECT data.......being on the highway, with 65mph air going through the radiator fins, no cooling fan is necessary, so it should be off.....Therm should open at 190F, but it could vary a few degrees either way.......when a P0128 is set, you will see the ECT data go very low, maybe 160-170F, and if you drive on the highway for any length of time, the temp will stay in this range, and not reach 190F, and will set P0128.....Also while watching data, you watch the temp gage at the same time, to make sure they read the same.......have seen as much as 5-15F difference due to a bad cluster....
What you are looking for, with a normally operating thermostat, is for the ECT data to cycle from 190-200F, approximately, on the highway.......so when the therm closes, temp will start to rise.....can reach as much as 200F, before it drops back down to 190F, because the therm has opened....have to remember, temps are not instantaneous......it takes awhile for the coolant to flow out of the engine through the radiator and then back to the engine......as it enters the engine it's lower than when it left, but by the time it gets back to the ECT sensor, it has picked up some heat from the engine, so this is a gradual rise and fall we have here.....So if I see this aprox 190-200 cycle on the highway, I know the therm is ok....
Now, you check the cycling of the coolant fan.....You let the car idle in park, and since no air is flowing across the radiator, temp will really start to rise.....I"m guessing your low speed fan comes on at about 218F.......when the fan comes on at 218F, temp can still rise until the cooled, coolant returns to the engine.......but with the fan continuously running, temp will probably drop to about 210, and the fan shuts off.....temp could still drop a few more degrees.......then the temp rises, and we have another repeated cycle of 210-220F(approx)....If you are in heavy traffic, on a hot day, the low speed fan can't handle the the high temp, and if the coolant reaches 228(once again this is a guess on my part), then the PCM commands the fan(s) to high......the temp could actually rise a few degrees more, before the effect of the high speed fan is realized.......when it approaches 218F, the speed could drop to low speed.....
This is about the only way, that the system can be truly checked (especially if the gage is slightly off)......
As I stated the car cooling fans do not come on at all unless the AC is running. If I let the car idle the engine goes all the way to the red point with no fans coming on. If I turn on the AC the cooling fans come on at high speed and the temp goes to normal in abought 5 minutes. Now that is colder outside I can keep the engine at normal temp by driving above 20 miles this forces air through the rad if I am in stop and go traffic I have to turn on the AC or turn on the front and rear heater and that keeps the engine from over heating. This is the problem. I can make the fans run at low speed by placing a ground on relay number 1 Problem is this caused and engine light to come on and when I read the code it pointed to relay number 1 been defective The interesting part is the PCM is reading either the voltage or the ground I placed on relay 1 where the PCM should have placed a ground. Strange thing is I had the same problem on my 1999 Olds 3.8 I fixed that by buying a harness that pluged into the rad fans and I could then flip a switch to turn on the fans in low or high speed.
Is it overheating? If you manually run the fan, it doesn't overheat? Have you checked coolant level in the radiator and the reservoir, when the engine is COLD?
There is nothing wrong with the cooling fan circuit, because it runs with the A/C on.......the circuit is controlled by the PCM, for A/C cooling AND for cooling off the engine.....
First off, a Tech II is the scan tool used by GM techs to diagnose vehicles....
When I check a car for a P0128, I take a vehicle at normal operating temp, out on the highway and cruise at 65 and watch ECT data.......being on the highway, with 65mph air going through the radiator fins, no cooling fan is necessary, so it should be off.....Therm should open at 190F, but it could vary a few degrees either way.......when a P0128 is set, you will see the ECT data go very low, maybe 160-170F, and if you drive on the highway for any length of time, the temp will stay in this range, and not reach 190F, and will set P0128.....Also while watching data, you watch the temp gage at the same time, to make sure they read the same.......have seen as much as 5-15F difference due to a bad cluster....
What you are looking for, with a normally operating thermostat, is for the ECT data to cycle from 190-200F, approximately, on the highway.......so when the therm closes, temp will start to rise.....can reach as much as 200F, before it drops back down to 190F, because the therm has opened....have to remember, temps are not instantaneous......it takes awhile for the coolant to flow out of the engine through the radiator and then back to the engine......as it enters the engine it's lower than when it left, but by the time it gets back to the ECT sensor, it has picked up some heat from the engine, so this is a gradual rise and fall we have here.....So if I see this aprox 190-200 cycle on the highway, I know the therm is ok....
Now, you check the cycling of the coolant fan.....You let the car idle in park, and since no air is flowing across the radiator, temp will really start to rise.....I"m guessing your low speed fan comes on at about 218F.......when the fan comes on at 218F, temp can still rise until the cooled, coolant returns to the engine.......but with the fan continuously running, temp will probably drop to about 210, and the fan shuts off.....temp could still drop a few more degrees.......then the temp rises, and we have another repeated cycle of 210-220F(approx)....If you are in heavy traffic, on a hot day, the low speed fan can't handle the the high temp, and if the coolant reaches 228(once again this is a guess on my part), then the PCM commands the fan(s) to high......the temp could actually rise a few degrees more, before the effect of the high speed fan is realized.......when it approaches 218F, the speed could drop to low speed.....
This is about the only way, that the system can be truly checked (especially if the gage is slightly off)......
As I stated the car cooling fans do not come on at all unless the AC is running. If I let the car idle the engine goes all the way to the red point with no fans coming on. If I turn on the AC the cooling fans come on at high speed and the temp goes to normal in abought 5 minutes. Now that is colder outside I can keep the engine at normal temp by driving above 20 miles this forces air through the rad if I am in stop and go traffic I have to turn on the AC or turn on the front and rear heater and that keeps the engine from over heating. This is the problem. I can make the fans run at low speed by placing a ground on relay number 1 Problem is this caused and engine light to come on and when I read the code it pointed to relay number 1 been defective The interesting part is the PCM is reading either the voltage or the ground I placed on relay 1 where the PCM should have placed a ground. Strange thing is I had the same problem on my 1999 Olds 3.8 I fixed that by buying a harness that pluged into the rad fans and I could then flip a switch to turn on the fans in low or high speed.
Rolm
10-20-2012, 05:45 PM
More info I found on the web
I own my own shop for years I have all dealership diagnostic equipment for all makes and models, I experienced alot of these problems first thing to check for is what the coolant temp sensor is reading if it is damaged or not then check for power and grounds the most common failure with these fan problems is the pcm the unit for the fan relay control which is a resistor that limits current to the fan relays to control low or high speed depending on the command of the motor, Most common failure with the coolant fans not comming on the chevy venture is the pcm or known as the power train control module located inside of the air box to the left side of the engine by the air cleaner. Hope this helps you out. Just remember to check your coolant temp sesnor for faulty readings which would cause your fans not operate also.
I own my own shop for years I have all dealership diagnostic equipment for all makes and models, I experienced alot of these problems first thing to check for is what the coolant temp sensor is reading if it is damaged or not then check for power and grounds the most common failure with these fan problems is the pcm the unit for the fan relay control which is a resistor that limits current to the fan relays to control low or high speed depending on the command of the motor, Most common failure with the coolant fans not comming on the chevy venture is the pcm or known as the power train control module located inside of the air box to the left side of the engine by the air cleaner. Hope this helps you out. Just remember to check your coolant temp sesnor for faulty readings which would cause your fans not operate also.
Rolm
10-21-2012, 08:51 AM
This is the cooling fan circuit:
46817
Probably the PCM is detecting that you are forcing the signal pin low. You should be able to avoid that by adding a diod in series with the signal from PCM to block the backcurrent and a pull up resistor to keep the signal high.
Hi
As a second thought I will do what you suggested I did find a nice diagram, See link. I do understand why the diode is there buy why is the resistor need at the ground point.
http://www.wildweasel.ca/HowTo/Auto/J-Body/FanSwitch.aspx
46817
Probably the PCM is detecting that you are forcing the signal pin low. You should be able to avoid that by adding a diod in series with the signal from PCM to block the backcurrent and a pull up resistor to keep the signal high.
Hi
As a second thought I will do what you suggested I did find a nice diagram, See link. I do understand why the diode is there buy why is the resistor need at the ground point.
http://www.wildweasel.ca/HowTo/Auto/J-Body/FanSwitch.aspx
Rolm
10-22-2012, 01:35 PM
I did complete the diode and resistor on the circuit and it seems to work perfect with engine check light. The next project will be to wire-up a relay from a switched 12v + and create a switched ground. I do not want to rely on turning on and off the fans manually
Rolm
10-23-2012, 11:28 AM
I also completed the relay that turns the fans on when the engine is running and off when engine is not running, no need to remember to turn the fans off & on. I also installed a kill switch to keep the fans off during cold winter mornings. It was a long road to this point but at least I will not fry the engine and transmission fluid. If I find a 2005 PCM at a reliable price I may try that fix.
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