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Old 06-18-2017, 03:15 PM   #1
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Strange fan behaviour

Hello everyone!


I have another one issue linked or not with this https://www.camaroz28.com/forums/gen...mp-lt1-885697/ one.
Need your advice and suggestions!


About month ago when my water pump started to leak, exactly that day I tried to reach home and in a half of my way I visited a shop where I parked my car and switched off the engine. When I returned to my car I noticed that tha fan is still tries to cool down the engine and some coolant leak form the pump detected. I thought was that some air passed to the water pump and there is no any coolant around the ECT sensor and it gives to the PCM a wrong data about the temperature. So I drove to home and all the way fan was working. Then at home I switched off the engine but the fan was working too. I don't know how the fans work on these cars from the factory, but mine often work some time after the engine is switched off - it is about 1-2 minutes in winter and up to 5-10 mintutes in summer. But this time it is already passed about 20 minutes and the fan is still working. So I went to my fuse box and tried to pull out all three relays and also a 10A fuse. But the fan still worked. Then I decided to disconnect the battery and it helped. I gave two hours to the engine to cool down and connected the battery again - fan didn't start again. That was the last day I used the car.
Two weeks ago I tried to start the car but the battery was discharged to 6 volts and it was surprise for me.
Today I brought well charged battery to my car, connected it. Turned a key to the 'on' position but didn't start the engine and then swithed off again and pull out a key. And in 20 seconds the fan is started again and yes - on a cold engine that didn't run about a month. Also tried to pull out all relays and fuses - didn't help. Also a fuse for PCM.


I know that my car is '95 and has a three relay configuration when two fans work at low speed and at high when it needed. But my car has a setup when the second fan is operated by the manual switch and only runs when I switch it. But what can be with my first fan??? How to check it?


Within a few days I will receive my own built cable to read the PCM about what temperature is from the ECT sensor and what fan relays it commands to run or not. But I think something is wrong with the fan.




Thank you very much!
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Old 06-18-2017, 05:26 PM   #2
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Re: Strange fan behaviour

Extremely difficult to sort out what appears to be a wiring issue, maybe a short, without knowing how you supplied power and ground to Fan #2 to make it run based only on your switch, and independent of the PCM control circuit. Assuming you have totally disconnected Fan #2 from the relays. Did you continue to supply (unswitched) 12 volts to Fan #2 from the fusible link at the red + box near the battery?

Also hard to understand how Fan #1 would operate at both low and high speeds, without Fan #2 available to be switched between series and parallel by the relays to change speed.

Might want to take the late production fan control diagram and mark up the changes you made.

http://shbox.com/1/fan_schematic_1995.jpg

While the 1995 factory setup supplies unswitched 12 volt power directly to the load side of the fan from the battery, the power is only connected to the fans when the relay control side is activated, the relay control side uses SWITCHED power.

That was changed in later years, maybe in 1998 for the LS1 cars, so the fans can run with the ignition switched off. Is your car an "export" model, which may have differences from the US models?

Last edited by Injuneer; 06-18-2017 at 05:37 PM.
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Old 06-19-2017, 02:08 AM   #3
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Re: Strange fan behaviour

Thank you very much!


Quote:
Originally Posted by Injuneer View Post
Extremely difficult to sort out what appears to be a wiring issue, maybe a short, without knowing how you supplied power and ground to Fan #2 to make it run based only on your switch, and independent of the PCM control circuit.
I know that to trace a problem is too difficult exactly because fans setup is not stock, it is difficult to me too. And the main problem of tracing is that this setup was done many years ago when this car was in the USA, the Powerdyne supercharger is also goes from that early years. So I brought this car two years ago already with all these modifications.


But I will try to trace fans wiring if you tell me where to start and where to look at.


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Assuming you have totally disconnected Fan #2 from the relays.
I think you are right, cause it is fully operational by my hand. Someone built in a tumbler switch in ashtray. So when it is very hot and I'm in the traffic jam, I just switch that tumbler on and the second (or the first) fans starts to cool down an engine. Also I will try to find what exact fan is operating automaticaly - passengers or drivers side.


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Did you continue to supply (unswitched) 12 volts to Fan #2 from the fusible link at the red + box near the battery?
Oh, that red oval box. Do you think that I must start to trace from that box? I will pop up front of the car to look at fans and to find where the wiring is going to. Also I will get some photos of that red box and harness around it, cause I saw som double-fuse box near, and maybe you can tell me what is that about.

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Also hard to understand how Fan #1 would operate at both low and high speeds, without Fan #2 available to be switched between series and parallel by the relays to change speed.
I have a surmise that this fan operates at two speeds like it should to do. Why? Beacuse I never heard it run at low, when it runs it is always very noisily, so I can hear it when it starts even when the engine is running and also hear it from my house window situated on fifth floor, when the engine is just switched off and the fan is yet running for a while.

Quote:
Originally Posted by Injuneer View Post
Might want to take the late production fan control diagram and mark up the changes you made.
http://shbox.com/1/fan_schematic_1995.jpg
I'm so dumb in electric, but i will try to collate what is in my car with that is in that diagram. Also if I will know where every element of the diagram is situated in the car, it will be much esier to me to find it or not and to build real diagram of my car fan setup.

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While the 1995 factory setup supplies unswitched 12 volt power directly to the load side of the fan from the battery, the power is only connected to the fans when the relay control side is activated, the relay control side uses SWITCHED power.
So you said that in factory configuration for the 1995 cars it is impossible to run the fan when engine is off and keys in my hands???

Quote:
Originally Posted by Injuneer View Post
That was changed in later years, maybe in 1998 for the LS1 cars, so the fans can run with the ignition switched off. Is your car an "export" model, which may have differences from the US models?
I think that my car was done for the US purposes, cause my speedo is in miles first and odo too, also a light setup is not european. Also I can provide my cars VIN if it helps to retrieve some important info. Here it is - 2G1FP22P3S2161187.
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Old 06-19-2017, 11:39 AM   #4
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Re: Strange fan behaviour

All the components of the cooling fan control system are shown on the electrical diagram I linked above. You are aware of the location of all of these, now that you know where the battery "+" box is located, and the info relative to connector C100..

PCM
Underhood fuse/relay box (3 relays and Fuse #6)
Dual fans
Fusible link
Connector C100 (see below)

The only way the fan(s) can run with the key in the "off" position, and the relays missing is if the fan is powered directly from the 12 volt source. Your switch can be used to interrupt the 12 volt source, with fan #2 permanently grounded; or fan #2 is permanently connected to the battery box 12 volt power, and the switch connects the fan to a ground.

Shoebox has a photo and a diagram of one way to add a manual fan switch. It shows you where connector C100 is located. This would be a good place to start looking for a wiring alteration.

http://shbox.com/1/fan_switch_wires.jpg

http://shbox.com/1/fan_sw_diagram1.jpg
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Old 06-20-2017, 02:36 AM   #5
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Re: Strange fan behaviour

Thank you very much.
Quote:
Originally Posted by Injuneer View Post
now that you know where the battery "+" box is located
Are you saying about that red oval box with big plus sign under the hood on passenger side?
Quote:
Originally Posted by Injuneer View Post
Fusible link
What is this? Where it is located under the hood?
Quote:
Originally Posted by Injuneer View Post
The only way the fan(s) can run with the key in the "off" position, and the relays missing is if the fan is powered directly from the 12 volt source. Your switch can be used to interrupt the 12 volt source, with fan #2 permanently grounded; or fan #2 is permanently connected to the battery box 12 volt power, and the switch connects the fan to a ground.
I think that this way my fan #2 connected - this is the fan that located on passengers side. I have tested it yesterday - it work fine - starts from the tumler switch in the ashtray and goes of the same way.
I will try to find out how the fan #1 (drivers side) works. I can't understand how it starts when the temperature goes up, but at the same time it is relays and fuse independent? Could someone put an independent temperature sensor somewhere? I even don't know exactly where, maybe to the radiator, but I never saw there some strange, looks like stock.
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This would be a good place to start looking for a wiring alteration.
Yes, I will try to start tracing there.
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Old 06-20-2017, 10:20 AM   #6
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Re: Strange fan behaviour

Also try and trace the wires from the switch in the ashtray, locating where they pass through the firewall
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Old 06-23-2017, 04:04 AM   #7
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Re: Strange fan behaviour

O.k. I have minor update about this issue.
Yesterday I've checked a PCM.
  • Went to my car and connected both leads to the battery;
  • Drivers side fan had instantly run;
  • I've got in the car and turn the key to the run position, so all the bulbs on my instrument cluster lighted on for a while and fuel pump pumped a gas;
  • I've connected my laptop to the PCM, the drivers side fan is still working and SES light is on (but it always stays on while the key is in run position but the engine is still off);
  • Checked the Scan9495 for the ECT sensor data - it is 82 degrees by Fahrenheit, but actual weather temperature was 68 degrees at that time in the evening, I think it is normal, cause my car didn't start about a month;
  • Started the engine for a while just to be confident that it is still able to run, so I can see that the engine is running fine, and coolant temperature rised to 90 degrees within a minute, then I have switched off the engine, the drivers side fan ran all this time;
  • Just disconnected both leads of the battery to shut down the fan.
Unfortunately I didn't test the ECT sensor with my DVM, cause I can't access it through the intake elbow and several hoses with DVM's leads in my hand.


So I assumed that my drivers side fan doesn't control by PCM. Scan9495 shows no of the relay is powered whle the fan is working, or the fan takes a power and a ground somewhere else.


http://www.mediafire.com/file/b88bo1...nt_temp_01.jpg
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Old 06-23-2017, 08:19 AM   #8
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Re: Strange fan behaviour

Seems like you should do Injuneers suggestion in Post #6 and trace the wires from the switch in the ashtray to where they go to help you figure this out !
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Old 06-23-2017, 09:02 AM   #9
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Re: Strange fan behaviour

Thank you! And yes, I will do it within a few days. But this was just one point of the check list - to check the ECT sensor.
But that switch in the ashtray controls passengers side fan only. First of all I will try to trace drivers side fan that operates automatically and for now it is failed.
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Old 06-24-2017, 01:08 PM   #10
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Re: Strange fan behaviour

Hello again!

Long story short. It took me only first five minutes under the car to get frustrated!

So, tracing the wires clarified me that my cooling fans system was completely modified compared to the stock one. Someone decided that he doesn't trust the GM way to cool the engine. So for now cooling fans system is completely separated from the ECT sensor in the water pump and the PCM. It works like... ...just look at the my diagram...

http://www.mediafire.com/file/gq2tyv...ns_Diagram.jpg

After the discovery I took that relay for test. And if I connect 12 volts to the relay it works well - starts clicking. I assumed that if relay is healthy than the issue is in that custom ECT, that is installed in the hose that goes from thermostat to the radiator. I don't know why it is failed. But there is an easy way to go, just replace it while replacing a water pump, when all of the coolant will be drained.

But I will try to find a way to return to the stock fan system setup, when three rerkay system is used and both fans operate low and high speed togetger.Thus I need to test all the wiring between PCM, fuse box and fans.Diagrams and images of stock wiring of the fans system will be the best.
Thank you very much!!!

Last edited by Novo; 06-24-2017 at 01:13 PM.
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Old 06-24-2017, 02:01 PM   #11
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Re: Strange fan behaviour

Would appear that the "sensor" in the coolant hose would actually have to be a thermal switch, providing an on/off control at a specific temperature.
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Old 06-24-2017, 02:22 PM   #12
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Re: Strange fan behaviour

Yes, you right! Sorry it is my fault, that I called it a 'sensor', but I meant exactly a switch as you corrected me. Thank you. I don't know even a trigger temperature of this switch.
Why do people sofisticate all the things around? The stock setup looks good, reliable and convenient for using.
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