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07-21-2014 #1
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- Dec 2004
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- 381
Thermo fan switch or temp sending unit difference?
Almost done installing my PRC dual fan setup in my 67 Camaro but I have a few questions reguarding the temp sending unit for my autometer gauge, the thermo switch form PRC and my Atomic EFI from MSD. Each one of these has there own switch or sending unit with them. I prefer not to have to use all 3 if I can get away with.
1. A sending unit and a thermo switch are two different things correct?
2. Is it possible to run wires to one switch or sending unit and have the gauge work and the fans work at the same time.
3. The MSD Atomic EFI can control the fans but the instructions suck. All it says that I run a wire to fan 1 and fan2 ground and thats it. Does this mean I still have to use a thermo switch for the fans separately instead of the atomic efi sending unit?
Sorry for all the questions! Electrical is not my forte! All this is to get rid of a switch or two if I can.
Thanks, Erik
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07-21-2014 #2
Registered User
- Join Date
- Feb 2009
- Location
- muggy midwest
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- 533
More than likely the MSD EFI provides (2) ground outputs for triggering relays which in turn control the fans. Personally, I'm not a fan of running fans seperately-I would suggest running them in parallel. If you would like more info on a dedicated 3-speed setup for your fans, I can offer some assistance. PM me for details....it irritates me that so many companies offer fan/radiator combos with no reliable fan control system already pre-wired and ready to go.
"...if at first you don't succeed, try again.
If you still don't succeed, then quit-no sense being a damn fool about it..."
-W.C. Fields
HARNESSWORX
(formerly gmachinz)
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07-24-2014 #3
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- Dec 2010
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- St Louis
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- 453
The sender for the gauge is totally different and needs to operate on its own. No you cant hook anything up to it.
If the efi has 2 fan outputs, it most likely has 2 outputs that each ground a relay for a fan. That's all that is needed. One will come on at a higher temp than the other. You can wire these each to an individual fan or wire both together to operate both together at 2 speeds (GM operates this way on LS motors).
My preference is to run 1 fan by the ecu, the other by a temp variable sender and/or the AC trinary switch. Allows adjustment without a computer, increases coolibg with AC. Uses 2 separate systems so if 1 fails, you still get home.
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