FANS (and AC)

[FAKKY]

Bought the BP AUTO DIY harness some time ago. Been working on the truck for almost 3-4 years. I couldnt determine how I had wired the truck so far back and was concerned AC wasn't done correct so pulled it all apart.

Here is a pic of the wiring as it comes for the BP auto harness.



The problem is that the FAN#1 has a smaller gauge green wire that is going to the engine harness ..... assume that is the signal (ground wire) received by sensor/ecm.

The blue (Fan#2 ) does not. The smaller gauge wire is free floating once it leaves the BP harness.

Is this due to my original donor vehicle only having 1 fan ? (2007 Hummer H2) and 1 wire control.

How would I go about making the 2nd fan work.

I want the 1st fan to control the radiator fan.

The 2nd fan I want to control the AC condenser fan with a binary switch (so always on as soon as the switch is enabled in cab).



The original instructions only say

Engine Connection Wiring Guide
=====================

** Dark Green - Fan1 Relay Control - This is the signal wire from the ecm/pcm that turns on the the low speed or first stage cooling fan. This is a ground signal.

**Dark Blue- Fan2 Relay Control - This is the signal wire from the ecm/pcm that turns on the the low speed or first stage cooling fan. This is a ground signal.



Chassis Connections Wiring Guide
=====================

Dark Green 12 Gauge - Fan 1 30A - This is the 12v feed to your low speed or first stage

Dark Blue 12 Gauge - Fan 2 30A - This is the 12v feed to your high speed or second stage

[FAKKY]

Think I worked out one part .....

Going back to LT1SWAP pinouts ..... looks like

C1 BLUE Pin #42 controls Fan 1
C2 GREEN pin #33 controls Fan 2

Doesnt look like I ever added a wire/pin for C2. Maybe as I was thinking to control condensor fan independently of the ECM.



So Should I add Pin #33 on the green ... and then have both fans controlled by ECM.

Not sure exactly when the condensor fan should really come on and off.

[kglowacky]

either way c2 needs to come on when you turn on the ac. on new cars the minute you turn on the ac the c2 fan comes on. There are people on this forum that know a lot more then me on how to connect these . Many add a third relay but since you don't have a ecm 2 ground trigger I would think at the least control your c2 by the ac compressor.

[FAKKY]

I think C1 and C2 wires are just ground signals to the Fans. I.e used to activate a low and high speed fan (fan1 fan2)

So thinking ......

Use the existing pinned C1 blue pinned 44 and associated relay to control main engine fan only. Basically come on and off as per engine temp and PCM tables.

For AC/condensor fan.
Just wire it with a binary switch like this.




Only downside is that the condensor fan will be on anytime the AC is on ..... even in highway speed traffic etc

[ls1nova71]

Adding the high speed fan wiring to the PCM may or may not do anything, it depends on if it was added in the tune if the original truck didn't have two electric fans, I'm not sure what a 2007 Hummer came with. As for hooking up the A/C part. I would skip the binary switch and get a trinary switch that is made to do the job. That way, the fans wont always be on whenever the A/C is turned on. It will shorten the life of the fans having them on all the time, and as you said, you don't need them on when you're on the highway since there will be enough airflow without them. By hooking it up to a binary switch, both the compressor and fan is going to come on at the exact same time which is going to put a pretty good load on the electrical system which could cause the engine to bog down for a second whenever it comes on. However the worst part is that the fan wont be on if the pressure gets too high, just when you need it the most, because the binary switch will shut the compressor off to avoid damage, therefor shutting the fan off at the same time. If you want to skip the trinary switch, then just wire the fan to come on any time the A/C is turned on but don't wire it through the binary switch.

[FAKKY]

Originally Posted by ls1nova71

Adding the high speed fan wiring to the PCM may or may not do anything, it depends on if it was added in the tune if the original truck didn't have two electric fans, I'm not sure what a 2007 Hummer came with. As for hooking up the A/C part. I would skip the binary switch and get a trinary switch that is made to do the job. That way, the fans wont always be on whenever the A/C is turned on. It will shorten the life of the fans having them on all the time, and as you said, you don't need them on when you're on the highway since there will be enough airflow without them. By hooking it up to a binary switch, both the compressor and fan is going to come on at the exact same time which is going to put a pretty good load on the electrical system which could cause the engine to bog down for a second whenever it comes on. However the worst part is that the fan wont be on if the pressure gets too high, just when you need it the most, because the binary switch will shut the compressor off to avoid damage, therefor shutting the fan off at the same time. If you want to skip the trinary switch, then just wire the fan to come on any time the A/C is turned on but don't wire it through the binary switch.

Thx nova.

1) So how would you wire the trinary switch in this case .....

And thats the part that guess I dont understand .... how does a trinary switch enable the FAN to still be on ..... when pressures get too high and compressor is shutoff.

2) Will any old trinary switch do or do I need the $35 VA one. HArd to read the LCOP and HCOP - but assume mostly standard ?

https://www.amazon.com/UAC-SW-4082C-...omotive&sr=1-2

[ls1nova71]

A trinary switch has 3 sets of contacts inside of it, one for low pressure cut off, one for high pressure cut off and a third for an electric fan. A binary switch just has two high and low contacts in it. To wire it up, the compressor would wire the same, one wire from the A/C switch on the dash would be on the high/low set of wires and then would go to the compressor. Then to wire the fan, you would ground one side of the switch and the other would go to the fan relay so it would get grounded whenever the pressure dictates the fan should be on. I cant say what wires are what, but they should be labeled or come with some kind of instructions saying what wire is what. As for what switch to use, all i have ever used were VA switches, but that one you linked looks like its the same thing, and its possible VA just puts their name on them.

[FAKKY]

thx sir
So is the idea with the trinary that the contact for say high pressure kicks in and shus off the compressor ...... but the circuit to the fan is still open ..... so still operates to bring down the pressure .....

[nsb29]

I would like to jump in here with some thing I’m in the same process and have a BP harness it is setup to use a pressure transducer to turn the fans on I told VA what I had and could they supply me with what I needed they sent me a binary switch with 4 wires not what I wonted and have no idea what to do with it

[FAKKY]

Originally Posted by nsb29

I would like to jump in here with some thing I’m in the same process and have a BP harness it is setup to use a pressure transducer to turn the fans on I told VA what I had and could they supply me with what I needed they sent me a binary switch with 4 wires not what I wonted and have no idea what to do with it

No idea on the VA side of it .... but BP sells all you need for that setup.

https://www.bp-automotive.com/air-conditioning-faq/

https://www.bp-automotive.com/produc...re-transducer/

[nsb29]

Originally Posted by FAKKY

No idea on the VA side of it .... but BP sells all you need for that setup.

https://www.bp-automotive.com/air-conditioning-faq/

https://www.bp-automotive.com/produc...re-transducer/

I ordered a weld in fitting this morning

[Low Elco]

I have 2 fans, wired 1 through a VA trinary and the other to the low temp kick on. Then wired the other (VA, fan 1) fan also to the high temp kick on. So one side works on the kick on at 195 deal and the other workd mainly with the AC, but can kick on if it gets real hot. I've sat in a drive through for 20+ minutes in 95 deg weather no problem. I love DQ, but that's another problem.

[derotoreut]

I would use a trinary switch and not binary. I have dual fans with Fan-1 wired to low fan temp set point, which doesn't come on until 200 deg F. The Fan-2 is wired to the high fan temp set point and also tied to the VA trinary.

[uxdesigner]

Check this out, he does a really good job of explaining the wiring and logic behind the switches.

https://m.youtube.com/watch?v=l604JCZx_ow

[72MARIO]

My wiring diagram

[72MARIO]

Just wanted to let you know how I did my fan setup using 1 fan but 2 controls. I used the green ac clutch power wire to control the trigger wire for fan 1 relay . Fan 1 was set on at 80f off at 280. Basically fan 1 is alway on using the pcm ground trigger. I set my fan 2 to come on at 205 off at 195. I just tied both the 10 gauge wires for the fan power together.
Both are set.to turn off at 30 mph. Works perfectly as long as you set fan 1 to be on constant.

I didnt want any more switches and wanted the ac fan off at road speed.