I'm not a big fan of running wires and switches into the cockpit, but was looking for better cooling fan control. I know that I can fake it by using the A/C controls, but that's a double-edged sword in the staging lanes because it engages the air compressor clutch.

I came upon a mod using a temp sensor probe, adjustable temp switch that is installed by jumpering across the fan relay closed contact wires. The author just took a visual of when his thermostat opened and set the switch to bring the fans on at the same temp. I guess you could even set it down lower when waiting for a run.

Here's the questions:
- Is this much ado about nothing? Will using the A/C controls suffice?
- Will an HPP3 setting accomplish basically the same thing?
- Does the SLP switch (or other mod) run the fans with the engine off?

Follow up question about the A4:
- Does the HPP3 increase shift firmness like the B&M switch (line pressure only)? If so, how do the settings compare? If they are similar, is a tranny cooler recommended either way?

Happy Thanksgiving to all - and thanks for helping a newbie come up to speed.

 

Funny you mention this, as I've tinkered with a lot of different methods.

I started on the '95Z with the JET Fan Switch, which has you remove the passenger side water jacket plug (which requires a 5/16" square fitting, sold pretty much only by Snap-On), that plugs directly into the wiring harness on '94-'97 models. Not bad, and with a 160 degree thermostat, did a great job. Then came the header install, and fried that damn sensor & the wires into a charcoal briquette. It's residue is for sale or keeps, if you want it. Harness complete, melted in half right before the sensor. The sensor is fine, just needs a new connector soldered to it.

Next came the SLP Fan Switch, which is in my opinion, the best fan control you can get. It comes complete with harness and switch, and is the simplest install of the two. Plug into wiring harness, route 3-wire switch connection through firewall (there are at least two holes big enough to do this, I used the same one my pedal assembly runs through, just pull the bottom panels off and replace, no biggie), and done. I did drill a hole into my dash to install the toggle, but you can opt not to, it's up to you. It's in a location that is very remote and blends with the Z28's dash completely, right behind the key between the steering column and rear window defrost. This switch has 2 speeds, high and low and middle position is factory default, which will kick the fans on at stock temperature, or if you have a HPP, whenever you have it set for. It's the best switch for consistency, as you can leave the fans on till you're ready to stage if you desire. I highly recommend this switch.

The third is the HPP, which I also use as my default on both 4th gens, and with the 160 powerstat, can even give you a couple extra ponies in warm weather (on the dyno anyways). There are 3 settings you can use, the 160 setting, the 180 and stock. I am using the 180 on my '94 during winter, as it already takes the thing forever and a day to warm up in this frozen tundra I'm currently living in. The function does not justify it's price though, if you're only using for the fan switch though. Just a great tool to have if you're switching gear ratios or in need of a multiple-functioning tuner without sending your ECM out for a flash.

Good luck!

Oh BTW: I notice it's a '98/newer, so never mind about the Jet Fan Switch, but anyways, the SLP switch will run with the engine off with the key in the on position. Just be careful if running the fans on high that you don't kill your battery, you have roughly 5-10 minutes of time before your battery can drain, depending on your existing charging system and if you're running other accessories, etc.