This is more for the people who have made the harness themselves rather than purchasing the nelson harness. My question is what did you do for the a/c. I have read that people have used a 3rd relay but im not really sure how you would wire it in where the load wouldn't be dependent on just the one relay, or do you use just one fan for the a/c? i can understand just using a 3rd relay if you are just using one fan with the ac on until the engine tempature rises... Also why couldn't you just use the negative triger for the compressor and hook that to the same part of the relay as the aux fan trigger? the only problem i could see with that is that could cause problems with backfeed into the pcm, but is that a problem? im just wondering how this is setup with a/c and the pcm controlling the fans

 

THe fan harness I made has a high and low switch. The PCM toggles the high side, which is either high, or the single fan on high, depending on the low side switch. The low switch is triggered with a piece I bought from O'Reilly's. It's a fan controller in itself, but they have it with 16 gauge wire claiming it will run 2 sets of fans. Instead of letting it power the fans, I just let it power the relays that power the fans, wired with much heavier wire (10 gauge, and 8 gauge for the main power wire).

The O'Reilly's piece has a temp probe that sticks in the radiator like the VSC does and will also trigger the fans (actually the low side in my setup) when the AC is on. So ... The O'Reilly's piece will turn on when the temp probe threshold is crossed or the AC is on. The PCM turns the fans on at a higher temp than the setting on the O'Reilly piece, which then kicks them on high. Very seemless and factory like.

 

The third(A/C) relay will be reversed. Instead of being triggered by a Neg, it will be wired so it can be triggered by a Pos and provide a neg for the other two relays making both fans turn on when the A/C is turned on.

More on relays:
http://www.partsexpress.com/resources/relays.html
http://www.eatel.net/~amptech/elecdisc/relays.htm

 

i like the nelson harness. and i reccomend not skimping on cooling. with the three relay system>>>
a/c on engine cool-1 fan on high
engine reaches temp-both fans on 50%
a/c on and engine at temp-both fans 100%

 

OK... Back to the original question. If someone DOES NOT WANT TO USE THE NELSON HARNESS, how do you wire it yourself?

There are a lot of people on here that are more than competent enough to hook up a few wires. Also, we would like to save money on the harness so we can waste our money on other things...

Sorry for the rant, just seems like EVERY post on how to gets directed to a harness you can buy. Can we just keep on topic ONCE???

Ryan

 

no that is why it is an opinionated forumn. take all info in and use it. yes it can be done with some relays and some wiring. there is a schematic on here do a search.

 

the search button works!!
https://ls1tech.com/forums/showthrea...ring+schematic

 

Always has. I used it and it worked great. However, since you seem to just post to use the harness when people ask how, search can be a real pain in the butt. I guess that bumps your post count though, right?

This post just turned into a useful one when you posted the link (I think you were trying to be a smart *** but you ended up actually answering the question asked, good job!!)

Thanks for some USEFUL information!

Ryan

Edit: If everyone on here used the search engine, there would only be about 100 topics... Asking the same question over and over gets different answers much of the time. By doing this, you can compare multiple posts and see what may really work. PCM pinouts do change over time so this could be useful to everyone ( example: 1998 Camaro pinout is totally different than a 99-02....)

 

whatever man. i meant what i said and i meant to answer the question. you asked what would work and we give answers. a smart ***. i can be. especially when some one as you begins to post up things like you did and now accusing me of **** i dont do. my post count is up since i answer a lot of questions and post opinions and experiences.

 

I think the 3 relay schematic in the mentioned thread is the one I used. Instead of using it solely for the AC though, I went and got a fan controller kit to run that side of the fan switch. It's a temp switch by coolant temp at the radiator and the AC, which I have them set to turn on at low. THe PCM turns on the high side.

I think I spent about 50 bucks on the relays and the kit. I had all the wires already. I think the Nelson harness is the same as the 3 relay schematic, just all loomed and stuff already.

02, have you been back to the track and sprayed that 80e yet? What did it run?