My 18 year old son has a raggedy 99 Silverado that I am helping him slowly fix up. He scored a set of electric fans from a local junkyard, but he obviously needs a tune to have the PCM control the fans. We discussed using a temperature switch on the coolant hose, but I think the PCM controlling it would be much better. I have a Blackbear tune on mine, and I have the temperature pin wired to pin 42 on the PCM, and the AC trigger wire spliced into the positive AC compressor wire. I figured I could wire his the same way, as mine has been working perfectly fine like that for 7 solid years now. He doesn't have a tune, nor does he need one (not any time soon at least). So is there a place that I can send his PCM and they will ONLY turn on pin 42 for the Efans? I remember seeing a website somewhere that said they can do it for about $65 or $75 or something like that, but I can't remember the name of that site for the life of me. So if you guys know of someone or somewhere that will do it for CHEAP, please let me know. Thanks.

 

I can take care of that for you and also do some basic tuning on it at the same time (assuming its all stock) for $165 shipped. Shift points, more timing, efans, torque management, etc. Send me a PM or an email at atomicfandp@gmail.com if you are interested. Thanks

 

If you're going to pay someone to alter the PCM, you may as well get the other benefits that Atomic mentioned.

If you absolutely don't want those features, a cheap fan controller with a 40A relay would be easiest. https://www.summitracing.com/parts/hda-3653/overview/

 

Where are you located?

 

X2 maybe some one local can help.

 

Thanks for the offer Atomic. That's a REALLY good price on a tune, but like I said he is FAR from ready for a tune. Right now, he is just looking for a way to operate the Efans as cheaply as possible. This truck has 265k miles on it, was beat to hell and back by my father in law, then he "gifted" it to my some when he finally realized that all the years of neglecting the truck caught up with him and it honestly need thousands in repairs just to make it a reliable daily. It's basically a beater that he uses to get to work and school, and it's a good teaching g tool as well, as I'm teaching him how to work on vehicles by fixing all the **** my FIL didn't. And yes it's all stock, some parts are original from the factory that should have been replaced a LONG time ago. It still has the original factory shocks for Christ's sake, it rides like absolute crap. So it needs a COMPLETE suspension overhaul, it has an exhaust leak, quite a few oil leaks, a leaking water pump, a bad AC compressor, ABS light and CEL lights are lit up, bad front wheel hubs, and quite a few other things. But the truck was free, and I know how to work on GM trucks, so it's at least a good start for my son as his first vehicle. So far, I've helped him replace the power steering pump and hoses, alternator, serpentine belts, spark plugs and wires, PCV valve, fuel filter, transmission fluid and filter, repaired several wiring problems (taught him how to solder) and a few other things I am probably forgetting right now. We have a LOOONG list of parts that need to be replaced, including the water pump and all the hoses, so he may as well replace the radiator and upgrade to Efans while we are at it.
Thanks for that link. I considered doing that, but I figured using the PCM to trigger the fans would be more reliable. This is a good "plan B" though. Due to my son's very limited budget (and mine as well ) we may very well end up doing a thermostat or temperature switch to trigger the fans if he can't find anyone to do it for really cheap. I can use a temp switch and the AC compressor wire to trigger the fans.

Located in Shreveport, Louisiana.

 

I'll do it for just shipping cost. I think if you are just going to use the PCM to command low speed fans and the A/C clutch to command high speed fans then your 99 OS will work for that. I know that if you want to have the PCM command both low and high speed by reassigning the auto air recirculation pin to fan operation for the high speed you have to upgrade the OS in the PCM to at least a 01 OS. I'm in OKC OK. If you want to ship me the PCM and include $13 for return shipping USPS Priority Mail then send me a PM for my shipping address.

 

Well after reading through this thread again I don't know if the 99 OS will even operate just the low speed fan correctly. It might require an OS update even for that.

https://forum.hptuners.com/showthrea...ersion-problem

 

After doing a lot of reading and Googling, it does indeed seem that the 99 computers are a complete clusterfuck. I think the best thing to do is just get a thermostat fan controller to get his fans wired up and working. If he decides to get a tune one day in the future, then I'll have him get a donor PCM off of a 2001 or later. The junkyards here charge about -$60 for them.

 

You don't need a newer PCM, you can load a newer calibration into the older PCM.

I use a 2002 operating system in a 99 computer. There is very little change between an 99-00 and the 01-02 PCM. This is how I get the fans to operate correctly in the early trucks.

https://www.performancetrucks.net/fo...h-info-536648/