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Username Post: Dual temp probe        (Topic#349664)
gchemist 
Senior Chevytalk Moderator
Posts: 24422
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
02-14-18 12:51 PM - Post#2724392    

Is anyone using a dual temp probe to activate electric fans? Volvo and BMW used switches in the mid '90's. They used to activate low and high fan speeds. If the head is not an option, (though GM did give us the option), far from the thermostat is a good place to install a probe?

'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 




1983G20Van 
Super Senior Member
Posts: 3718

Loc: Bedford, Texas, USA
Reg: 11-13-02
02-15-18 09:23 AM - Post#2724469    
    In response to gchemist

  • gchemist Said:
Is anyone using a dual temp probe to activate electric fans? Volvo and BMW used switches in the mid '90's. They used to activate low and high fan speeds. If the head is not an option, (though GM did give us the option), far from the thermostat is a good place to install a probe?



Just get one of the early 80s style thermostat housings for your truck. They had a port in them for an emissions TVS. Depending on the size of the temperature switch, either retap the hole to the thread size or use a brass reducer bushing and retap the inside of the bushing to match the switch. That way it is right at the thermostat and will activate the fans as soon as the outlet temperature hits the turn on point. I have done just that with the Volvo switch before. Keep in mind those switches usually deactivate the low speed when they enable the high speed but that is easy to overcome in a dual relay fan system with a single properly placed diode. The setup I built was controlling dual 4th gen F-car fans with the OEM 3 relay setup. 91*C/99*C switch points for the fans on a 195*F thermostat. Ran a little warm for my taste but the MPG was good with an otherwise stock 305 TBI engine. Also worth mentioning the 85-86 trucks had a thermostat housing with dual tapped holes to work with the temperature switch on the dual capacity accelerator pump q-jets.

1983 G20 Van, 350 TPI, Ported 906 Vortecs, Edelbrock 3817 Base, ASM oversize runners. Reed Custom Roller cam, 700r4, 12 bolt with 3.08 gears, Doug Thorley Tri-Y headers, true duals


Edited by 1983G20Van on 02-15-18 09:37 AM. Reason for edit: No reason given.

 
gchemist 
Senior Chevytalk Moderator
Posts: 24422
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
02-16-18 07:58 AM - Post#2724567    
    In response to 1983G20Van

My truck runs two switches for fans. One in the right head. The other is a trinary switch in the A/C system. The LS Camaro fans work great.

This mod is for a Dodge. SB 318 FI. The dual speed fan for cooling seems straightforward with a few parts. It's the A/C system causing the other problem. Dodge uses quick connect lines. GM uses threaded lines. It's easy to install a short line with a switch in a GM vehicle. The accumulator has odd shaped lines. I may have to ask an A/c shop to make customs lines. Or make quick adaptors to fit a Dodge accumulator.

'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 




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