Yes. I have actually "fixed" a loose/dirty connection just by unplugging a connector and then reconnecting it. Areas where they use salt or "brine" can cause havoc on things like that.
Rad Fans run with no key on cold engine
- Thread starter wifes_truck
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wifes_truck
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yes i agree salt and electrical stuff.... great combination... lol
The cover for the PCM (if this is what it is called on the truck), is covered pretty decent in a plastic enclosure. just in a bad place.... I didn't want to pull to ******* the main plug to dis-lodge the wires as room is tough to find where they located this thing. figured if its not broken, don't fix it theory kicked in. (looked way to clean) lol
cheers
The cover for the PCM (if this is what it is called on the truck), is covered pretty decent in a plastic enclosure. just in a bad place.... I didn't want to pull to ******* the main plug to dis-lodge the wires as room is tough to find where they located this thing. figured if its not broken, don't fix it theory kicked in. (looked way to clean) lol
cheers
wifes_truck
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Well, that was a short lived fix ... Last night she went to jump in and head into town for last minute store run...
Dead Battery ... only guess can be a parasitical on again off again fan problem ... why would a set of fans just turn themselves on for no reason?
On the relays it is fan 1 that controls this running. can anyone tell me if fan one is the one that is controlled by the A/C? we have no coolant charged in the A/C and do not use it. I am at the point of keeping this relay out of the relay box and having the truck just running with out for a while. that will eliminate the run/no run without a key or any power to the fans from relay #1.
I might need to pull the wire harness off the pmc and take an investigating look there, but, by looking at the condition of those wires I would probably be wasting my time.
Only other thing is maybe a mouse has chewed a ground wire somewhere... but then that on/off would run 100% of the time. As this problem is not 100% If the truck is turned on for 5 mins, and turned off no fans keep running. however just turn the key to on position off and back a few times, then pull key out of the ignition. Bamm fans turn on.
completely baffled on this one now.
cheers
Dead Battery ... only guess can be a parasitical on again off again fan problem ... why would a set of fans just turn themselves on for no reason?
On the relays it is fan 1 that controls this running. can anyone tell me if fan one is the one that is controlled by the A/C? we have no coolant charged in the A/C and do not use it. I am at the point of keeping this relay out of the relay box and having the truck just running with out for a while. that will eliminate the run/no run without a key or any power to the fans from relay #1.
I might need to pull the wire harness off the pmc and take an investigating look there, but, by looking at the condition of those wires I would probably be wasting my time.
Only other thing is maybe a mouse has chewed a ground wire somewhere... but then that on/off would run 100% of the time. As this problem is not 100% If the truck is turned on for 5 mins, and turned off no fans keep running. however just turn the key to on position off and back a few times, then pull key out of the ignition. Bamm fans turn on.
completely baffled on this one now.
cheers
You can just unplug the a/c compressor clutch and leave the relay or leave plugged in and cross the wires at the low pressure cut off switch and then unplug the relay to see if that shuts the fans off. If you turn the a/c on and the low pressure switch is crossed and the compressor is plugged in, that should turn on the fans and then unplug relay as you wish.
wifes_truck
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hi ron,
yes that is looking like what i will try tomorrow and see if it can be taken out like that. nothing is adding up for sure. Purchased a couple new relays just to see if that will make a difference. marked one of the old ones ( 2 same) with a black marker, and started unplugging the 4 pronged ones (2) and at first it stopped the fan for spinning... i was HEY maybe it is a relay.... so.... turned on the truck to see ... nope, fan went on after turning off the ignition...
will need to check into the deleting of the A/C stuff and seeing if I can bypass the sending unit for that fan.
cheers and cross fingers for tomorrow.
yes that is looking like what i will try tomorrow and see if it can be taken out like that. nothing is adding up for sure. Purchased a couple new relays just to see if that will make a difference. marked one of the old ones ( 2 same) with a black marker, and started unplugging the 4 pronged ones (2) and at first it stopped the fan for spinning... i was HEY maybe it is a relay.... so.... turned on the truck to see ... nope, fan went on after turning off the ignition...
will need to check into the deleting of the A/C stuff and seeing if I can bypass the sending unit for that fan.
cheers and cross fingers for tomorrow.
Good luck and let us know.
wifes_truck
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Well.... A friend came over today and said, "lets tackle this thing"
We retraced everything we could find that has a wire attached to it. took apart, tested, pushed, pulled, cussed and bled on, in, under or above this Tahoe.
For the life of us we could not find a sending unit beside the water pump, thermostat housing. Just doesn't seem to be there. The only sending unit we could find was above the #1 plug.
we disconnected all electrical for the A/C, and removed the relay and 10 amp fuse. cleaned all battery posts and checked all ground connections.
Everything we tested and tried was confirmed pointless by the test light we placed into the positive plug for the fan and grounded to batt. the light would just stay on, meaning we had not solved the fan on situation.
For a last attempt i said, well lets take out that wire connection for the PMC. this time we took it completely off the plug in. we looked it over, and as suspected, the whole thing looked spotless. no corrosion nor any sign that would make a person think a fault was there.
We replaced it all back up. re-hooked the battery and waited for the test light to come on .. and waited ... and waited ... AND WAITED ........
Nothing .... we looked at each other with that WTF expression ....
been 3 hours now, wife took the truck to town 2 hours ago and its been sitting for an hour now... still nothing .....
One thing is 100% for certain ... I am not holding my breath that it is fixed (been down that road) LOL If this shorts out again I will take out the #1 fan relay and I have a Flex-Lite probe and relay system new in package on the wall in the shop that i was saving for a project (but the fan I bought for it came with its own controller. so i will just bypass the Tahoe relay system and build my own fan controlling system.
this is to much work and effort...
cheers and fingers crossed.
We retraced everything we could find that has a wire attached to it. took apart, tested, pushed, pulled, cussed and bled on, in, under or above this Tahoe.
For the life of us we could not find a sending unit beside the water pump, thermostat housing. Just doesn't seem to be there. The only sending unit we could find was above the #1 plug.
we disconnected all electrical for the A/C, and removed the relay and 10 amp fuse. cleaned all battery posts and checked all ground connections.
Everything we tested and tried was confirmed pointless by the test light we placed into the positive plug for the fan and grounded to batt. the light would just stay on, meaning we had not solved the fan on situation.
For a last attempt i said, well lets take out that wire connection for the PMC. this time we took it completely off the plug in. we looked it over, and as suspected, the whole thing looked spotless. no corrosion nor any sign that would make a person think a fault was there.
We replaced it all back up. re-hooked the battery and waited for the test light to come on .. and waited ... and waited ... AND WAITED ........
Nothing .... we looked at each other with that WTF expression ....
been 3 hours now, wife took the truck to town 2 hours ago and its been sitting for an hour now... still nothing .....
One thing is 100% for certain ... I am not holding my breath that it is fixed (been down that road) LOL If this shorts out again I will take out the #1 fan relay and I have a Flex-Lite probe and relay system new in package on the wall in the shop that i was saving for a project (but the fan I bought for it came with its own controller. so i will just bypass the Tahoe relay system and build my own fan controlling system.
this is to much work and effort...
cheers and fingers crossed.
Ever since you said that you wiggled wires down there and it stopped for a while till it came back on, I had said to really get in there and unplug it and inspect it and see what you could see, see post #17...................................................................but noooooooooooooooooooooooooooo, you would not take that chance and I understand why but myself, I have always wanted to get to the bottom of things. Even if what you did does not fix it, it has something to do with that circuit on that wire. Intermittent electrical problems are the worst there is and can make you lose your mind. My best time with these is when someone else, YOU, are doing it. I sometimes do not have the patience for sure. I do hope it is fixed, I really do. If the problem comes back, I feel for ya. I do. But if it doesn't come back, well I will rub it in a little bit. Well, maybe more than a little bit. Who am I kiddin'. I will rub it in a LOT!
wifes_truck
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well it was short lived. took the dog out for a squirt.... guess what... the fans were running so I am at a complete loss why. How is it possible a truck that is just sitting there can start up on its own for no reason? Won't be happening again tonight, unplugged the fans .... So much for was it the PCM? truck sat 4 hours, and i was out there an hour ago to check it. and just now it is running.... i give up.
cheers any options besides a KEG TNT?
cheers any options besides a KEG TNT?
Well, hell, my gloating ends........damn it. On this year, does anyone know if there is a separate coolant temp sensor and a separate sender for the gauge, like it used to be? Or am I just old enough and out of the shops long enough that it has all changed enough where I am out of the loop? I feel for ya, I do.
wifes_truck
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Hi Ron, I was hoping it was fixed. I would eat my words to not have to climb back into that engine compartment again... lol .. i have never seen or heard of anything like this before. Its almost like a Larel and Hardy sketch, or an inquisition of "who's on first". Wife did mention maybe bite the bullet and take the PCM to chevy dealer and see if the PCM is shot and they can reprogram it??? or buy a new one ... she does love the Tahoe ... It does run strong.
Loss for ideas now. I feel your caring ... LOL thanks for the encouragement.
cheers
Loss for ideas now. I feel your caring ... LOL thanks for the encouragement.
cheers
Tonyrodz
Resident Resident
Hmmm, I wonder if maybe some moisture and corrosion got to the pcm. It is possible.
Like Tony says, There is a real possibility that the PCM is FUBAR on that circuit. Typically the PCM is the last thing to think is bad. It is typically the other parts/items in the circuits that are exposed to real world exposed problems like temp and moisture and salt and such and in this case, that pcm is exposed. I really would be the last person to point at a pcm, but maybe, like the lady says, that damn thing is jinxed.
Tonyrodz
Resident Resident
I had a pcm go bad once in my old express van. Took forever to find that was the problem. Had to replace it. Never had another issue afterwards.
wifes_truck
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Hi tony, ron,
Yes I am thinking that is the only thing left, the PCM. Maybe the problem is actually inside the box itself and this is the unseen ghost. as said all the wires going into it are spotless. That's where the head scratch comes from. Now question remains... bother with second hand and getting another problem child (possible) or biting the bullet and saying ouch to chevy on a 16 year old truck ...LOL should try a scrap yard 1 first to see if that changes anything i guess.
thanks guys, cheers
Yes I am thinking that is the only thing left, the PCM. Maybe the problem is actually inside the box itself and this is the unseen ghost. as said all the wires going into it are spotless. That's where the head scratch comes from. Now question remains... bother with second hand and getting another problem child (possible) or biting the bullet and saying ouch to chevy on a 16 year old truck ...LOL should try a scrap yard 1 first to see if that changes anything i guess.
thanks guys, cheers
mikeyss
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I'm thinking outside the box a little bit here... But could the fan motor itself have an internal failure that is causing a short?
wifes_truck
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hi mike.
I don't know how the fan(s) could be shorting, but you make an interesting question as only the drivers side fan is the one that I have been un-hooking and not the passenger side. The test light turns on instead of the fan being plugged in, so maybe i should leave driver side plugged in and test the passenger side. never thought about the other fan, but they are wired together in same configuration.
thanks
(PS) but that still doesn't answer the why the fans kick in 4 hours after the ignition is killed and no key in the truck.
I don't know how the fan(s) could be shorting, but you make an interesting question as only the drivers side fan is the one that I have been un-hooking and not the passenger side. The test light turns on instead of the fan being plugged in, so maybe i should leave driver side plugged in and test the passenger side. never thought about the other fan, but they are wired together in same configuration.
thanks
(PS) but that still doesn't answer the why the fans kick in 4 hours after the ignition is killed and no key in the truck.
Tonyrodz
Resident Resident
You won't be able to plug in a used pcm--it won't start. You can buy a good used pcm and have it flashed/programmed for your vehicle. I bought a brand new pcm for $200, and paid around $150 to get it flashed. These prices were in my area, yours may differ.
EDIT--Try looking into this--https://www.amazon.com/dp/B07N98MBR9/ref=cm_sw_r_cp_apa_i_I6H8Fb7A46ESF
wifes_truck
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Hey All,
Can anyone supply me with a real PCM wire plug code for a 2005 Tahoe? I am on this circle jerk merry-go round in google hell trying to find a wire diagram for this PCM. I want to double check the wires and the situation to the pins. Nothing I am finding is coherent to what I am seeing in the physical plugs versus the wire diagrams on line. From any wire diagram I am seeing that shows the relays and the PCM say/show:
High speed / low speed
Bank c1 = 80 BU
Bank c2 = 80 GN
Problem is, all diagrams I am finding show no such wires at those pin numbers. cannot find the proper PCM schematics
Nothing in this basic diagram states what actually sends the signal to the (PCM) to engage the fans. what/where is the sending unit that turns on the relays? or grounds the relays? or how does the signal get to turn on the fans at 200 degrees or what have you...
I will be putting the truck back into the shop soon to physically pull out the PCM, open wide the pin connectors, and I mean go over every wire that is in that group/plug to eliminate any signs or corrosion. is there a way to OPEN a PCM and inspect for corrosion? or it a sealed unit with no access?
cheers and thanks.
(still haven't ruled out plan B and re-wiring in a after market fan controller.)
Can anyone supply me with a real PCM wire plug code for a 2005 Tahoe? I am on this circle jerk merry-go round in google hell trying to find a wire diagram for this PCM. I want to double check the wires and the situation to the pins. Nothing I am finding is coherent to what I am seeing in the physical plugs versus the wire diagrams on line. From any wire diagram I am seeing that shows the relays and the PCM say/show:
High speed / low speed
Bank c1 = 80 BU
Bank c2 = 80 GN
Problem is, all diagrams I am finding show no such wires at those pin numbers. cannot find the proper PCM schematics
Nothing in this basic diagram states what actually sends the signal to the (PCM) to engage the fans. what/where is the sending unit that turns on the relays? or grounds the relays? or how does the signal get to turn on the fans at 200 degrees or what have you...
I will be putting the truck back into the shop soon to physically pull out the PCM, open wide the pin connectors, and I mean go over every wire that is in that group/plug to eliminate any signs or corrosion. is there a way to OPEN a PCM and inspect for corrosion? or it a sealed unit with no access?
cheers and thanks.
(still haven't ruled out plan B and re-wiring in a after market fan controller.)
Tonyrodz
Resident Resident
As far as I know it's a sealed unit--I could be wrong tho.
