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 Post subject: Wiring in a thermal fan in Sierra
PostPosted: Fri May 18, 2018 11:02 pm 
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Location: brisbane
So we have put in a thermal fan which comes on with the ignition. We have a switch tha allows us to turn it off when doing water crossings etc but the prefered option is for the ecu to controll it as it probably shoulnt be on all the time especiall when the engine is cold... I have tracked down the gti ecu pin out diagram from here...thanks...
https://www.redlinegti.com/forum/viewto ... cu+pin+out
and it tells me that 31 controls the fan..excellent.. but when I look for 31 ... there is no pin # 31....it is off to the left in a separate box with 32,33,34,and 35.... which all seem to go to pin 11 in the ecu...Very confusing... As you can tell this is all a bit of a mystery to me.... I was hoping there would be a wire/pin I could use to run to the relay that we fitted for the fan and the ecu could be the "switch" on the relay so the fan could be controlled by the ecu and we could over ride that in water.. Sorry if this seem a dumb question, but I can't work out the diagram at all, unless pin 11 turns on ALL of the things in the "box" eg..31,32,33,34 and 35... But that doesn't make sense..PS... the guy who made the loom didn't put in a wire for the thermal fan...aaahhhh...not sure why not.. he didn't do a very good job of the loom. The ecu was live ALL the time even with ignition off. Luckily I have a domestic sparky friend who sorted out the 3-4 things that the loom maker had got wrong.. It was a $400 loom so I was expecting it to be done right...


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 Post subject: Re: Wiring in a thermal fan in Sierra
PostPosted: Sat May 19, 2018 10:30 am 
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Location: Brisbane
I would need to dig out my wiring diagram to be sure, but I am fairly certain the fan is operated by a temp switch in the head and has no ECU control.

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 Post subject: Re: Wiring in a thermal fan in Sierra
PostPosted: Sat May 19, 2018 4:27 pm 
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Location: brisbane
That would make sense as it should be triggered by engine temp, but, like I said, there doen't seem to be any spare wires or switches or anything that weren't accounted for when we had this up and running..I was expecting a spare wire that said "thermal fan" on a tag but there was nothing...I am hoping for someone with a gti will pipe up and say.." ah yes, the fan is run of ecu pin bla bla " or " the fan gets a signal from bla bla switch located somewhere I haven't noticed.." Anyway , thanks for the reply . You suggestion makes sense..


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 Post subject: Re: Wiring in a thermal fan in Sierra
PostPosted: Sat May 19, 2018 8:12 pm 
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the thermo fan runs from its own temp sensor - there are 3 temp sensors. 1 for the ECU so it knows to swap out of the rich map settings for cold idle, 1 to run the temp gauge and the third runs the thermo fan. That 'box' you are looking at is a bunch of signals used to bump the idle up if there is an electrical load - like when the lights are on or the air conditioner is on.


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 Post subject: Re: Wiring in a thermal fan in Sierra
PostPosted: Sat May 19, 2018 11:49 pm 
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Location: brisbane
So.. the fan has a sensor within itself with no external trigger except for heat... ok.. Then I have a problem as I am not running a gti fan. I have an aftermarket fan that is, at the moment, turned on when ever the ignition is on. I understand now what the box represents.. things that would require a higher idle.. So I wonder if there is a way to turn the fan on when temp is high. So what I need is a gti fan that has a controller within itself that tells it to turn on and off. Is it a viscos type situation where a jelly within the fan solidifys when hot which engages the fan.. I shall investigate installing a gti fan.. I assume it bolts onto the front of the waterpump ..


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 Post subject: Re: Wiring in a thermal fan in Sierra
PostPosted: Sun May 20, 2018 8:37 am 
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Toomanycars wrote:
So what I need is a gti fan that has a controller within itself that tells it to turn on and off. Is it a viscos type situation where a jelly within the fan solidifys when hot which engages the fan.. I shall investigate installing a gti fan.. I assume it bolts onto the front of the waterpump ..
The fan is a simple electric motor that in a GTi is on the radiator. The fan sensor is in the block near the thermostat - power goes into the fan, out of the fan to the sensor and then to ground when it gets hot enough. Any aftermarket thermo switch / relay kit will work if the Gti sensor is unserviceable. Supercheap have a switch kit for the fans, although for their kit, you need to feed the capillary into the top hose to pick up the heat. Pretty simple kit that includes everything (including adjustable thermostat and relay) In a road going GTi, the fan is off most of the time.


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 Post subject: Re: Wiring in a thermal fan in Sierra
PostPosted: Sun May 20, 2018 10:24 am 
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Location: brisbane
Is it possible to get a photo of this fan sensor so I can see exactly where this is. Oh the joys of engine conversions .. Thanks for the replies.. I am slowly getting my head around this...There is a sender near there that is a simple male plug that has a wire connected into the new loom to the ecu. It is a real PITA to get to once the engine is installed as it is down under everything squeezed into the back of the engine bay.. With this engine in a Sierra the easy access you guys have to the end of the engine in a swift engine bay is totally gone. In a Sierra you also have the joy of all your heater hoses being right in among the mess there, as well as a 90 degree rotor cap that has your spark plug wires hindering any access from the top. You need to undo the mounts including transmission mount and slide the engine forward to get the dizzy cap off... :shock: ....I thought that sender was a temp sensor talking to the ecu but it sounds like it goes off to a "box" in the engine compartment ?? Am I missing some "hardware" ??


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 Post subject: Re: Wiring in a thermal fan in Sierra
PostPosted: Sun May 20, 2018 3:32 pm 
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The radiator thermo switch originally had a brown plug with a Blue wire with white trace and a blue wire. It's one of 2 sensors on the thermostat housing - the second sensor has a single terminal / plug with a Yellow with a white trace (that's the dash Temp Gauge) ECU sensor is into the block below the thermostat housing - blue plug.

Power goes to the thermo switch on the housing via the fan fuse and then via the Blue / white wire. When the temp turns the switch on, power goes to the fan via the blue wire, then from the fan to ground via the fan black wire.


Attachments:
File comment: Sensors and fan - best I can do without a scanner.
20180520_152850[1].jpg
20180520_152850[1].jpg [ 1.01 MiB | Viewed 148 times ]
File comment: Brown plug
20180520_150151[1].jpg
20180520_150151[1].jpg [ 943.89 KiB | Viewed 157 times ]
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 Post subject: Re: Wiring in a thermal fan in Sierra
PostPosted: Sun May 20, 2018 5:02 pm 
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Location: brisbane
Thanks Zedd for taking the time.. I have the brown plug with the Bl/wh and the blue wire ..It has the plug coming from the loom and going to the brown plug on the thermostat housing.. But those 2 wires just disappears into the loom and goes back to the ecu. We have had to unwrap the loom completely once and i am reluctant to unwrap it all again.. The is the single connection is already going to the original Sierra loom to the temp gauge so I have that sorted..

So.... I need to investigate the loom further before I go cutting into it and re routing that bl/wh wire through a "fuse" ( the sierra does not have a fan fuse as the fan is bolted to the water pump pully but I can use the fuse I bought and have on the fan wiring that I have installed to turn it on manually)... continue it then to that brown switch then the blue wire to the pos+ side of the fan and then earth the black wire from the fan to the chassis...Do I need to have it all kind of connected to the engine (which is out and in pieces) to run a meter over that bl/wh to see if it has 12 volts, or can I simply reconnect the battery with the engine out to check some voltages.. I don't want to freak out the ecu and fill it with error codes cause it is trying to talk to an engine that is not there.. (sorry if these questions seem a bit stupid). That bl/wh wire should have 12 v with the ignition on shouldn't it ?? I can't help wondering why the bl/wh wire runs to the brown switch and then both bl/wh and blue wires go back to the ecu ....why would he make the loom like that... surely he should have made allowances for the fan .......


Last edited by Toomanycars on Mon May 21, 2018 4:58 pm, edited 1 time in total.

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 Post subject: Re: Wiring in a thermal fan in Sierra
PostPosted: Sun May 20, 2018 6:27 pm 
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Because the fan motor consumes a fair wack of power there will be a relay the thermos switch activates. Find that.

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 Post subject: Re: Wiring in a thermal fan in Sierra
PostPosted: Sun May 20, 2018 6:33 pm 
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Joined: Wed May 09, 2018 11:48 am
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Location: brisbane
Being a Sierra, it won't have that unless you are talking about one of the 2 relays that came with the new loom. I have no idea what they are for. I have installed a relay, fuse and switch to run the fan manually so could I use the "blue" wire as the activation switch on the relay I have already installed in the engine bay..I could then run the "blue" wire to the relay via the dash switch so I can still manually turn the fan off in water..Will that work ok ???? Sorry for being a pain and thanks for the replies. I wish I was more electronically savy !!!


Last edited by Toomanycars on Mon May 21, 2018 4:54 pm, edited 1 time in total.

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 Post subject: Re: Wiring in a thermal fan in Sierra
PostPosted: Mon May 21, 2018 4:53 pm 
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Joined: Wed May 09, 2018 11:48 am
Posts: 86
Location: brisbane
I spoke to the loom maker and he has pointed me to the wire that is a trigger for the fan from the thermostat fan switch..It was the only left over wire that had no "TAG" on it to identify it...All I need to do now is connect it up to the fan relay I have installed as the "trigger" and run it via the on/off switch so it can be turned off for water crossings.. He also said that even with the engine out, as a test, I can reconnect the battery and with a bit of wire , bypass the thermo switch and see if the "fan switch wire" get 12v...


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 Post subject: Re: Wiring in a thermal fan in Sierra
PostPosted: Tue May 22, 2018 4:10 pm 
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Joined: Wed May 09, 2018 11:48 am
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Well that was such a simple thing once the "wire" was identified.. I simply cut the 12 volt feed that goes to the on/off water crossing switch and connected it to the "thermo" fan trigger wire instead for its 12v feed. So.. now the fan just comes on and off as the thermostat temp sensor tells it to and if he wants, he can switch it off at the dash... 8)


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 Post subject: Re: Wiring in a thermal fan in Sierra
PostPosted: Tue May 22, 2018 4:33 pm 
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Location: Napier
yay for a solution!

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