Vehicle speed sensor

sirstude · February 21, 2017, 10:41:50 AM

I ran into a problem on the Olds. I have a fan controller that needs a speed sensor to tell it how fast the car is going so I can shut the pusher fan down a highway speeds. I purchased a stand alone VSS, but don't know any way to wire it up without a computer. Seems to need about 5 volts to trigger it. Anyone out there have any ideas how to make this lash up work? Painless said I am just probably out of luck and it is their equipment.

Thanks
Doug

kb426 · February 21, 2017, 01:01:39 PM

My 1st thought it get a 12v dc to usb adapter. All usb is 5 volts. Do you have a cable drive speedo or vss driven?

sirstude · February 21, 2017, 01:24:52 PM

I wonder if I need to hit it with any power? I checked the wiring instructions see below and they say ground one side and connect the other to the ecu. The fan controller says to just tap the line to the ecu, but I wonder if it would be fine direct. Have to do some more thinking on this I guess.

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Instructions from painless on the VSS

THE VEHICLE SPEED SENSOR (VSS) IS TO BE USED WITH PART NUMBERS 60101, 60201, 60102, AND 60202. THE SPEED SENSOR IS SMOG LEGAL IN CALIFORNIA AND HAS BEEN ISSUED E.O. # D-371. THE VSS DOES NOT REQUIRE A BUFFER OR A DRAC. THE SIGNAL WIRE ATTACHES DIRECTLY TO THE HARNESS.
ONE LEAD IS CONNECTED TO GROUND (IT DOESN'T MATTER WHICH WIRE). THIS WIRE SHOULD BE CONNECTED DIRECTLY TO AN ECM GROUND.
THE OTHER LEAD (OUTPUT OR SIGNAL) IS CONNECTED TO THE VSS INPUT ON THE ECM. THIS IS THE BROWN WIRE LABELED VSS IN OUR KIT. ON SOME TRUCK TBI ENGINES, THE SHOP MANUAL WILL CALL THIS THE DRAC BUT IT IS THE SAME AS VSS. CHECK WITH THE APPROPRIATE SERVICE MANUAL FOR THE CORRECT WIRE

sirstude · February 21, 2017, 01:27:17 PM

Little more info, here is the wiring diagram for the controller (Painless 30141)

http://www.painlessperformance.com/Manuals/30141.pdf

enjenjo · February 21, 2017, 01:39:16 PM

I am assuming the VSS is a Hall Effect type. If it is, it does not need a voltage input, it will generate it's own voltage pulses. And if the fan controller can interpret a VSS, it will be doing so by counting pulses. So it should have some type of processor in it. So two wires from the VSS to the controller should be all that is needed.

kb426 · February 21, 2017, 02:04:08 PM

I agree with Frank. I have two different kinds of sensors that I mess with. A simple definition is ac generator. + and - is all that's on both of them. One makes way less voltage than the other. I didn't read through the manual. Does the fan controller specify how much voltage it requires to operate? Is it adjustable to compensate for different sensors?

enjenjo · February 21, 2017, 02:12:18 PM

Looking at the wiring schematic, if you connect the VSS push button wire to one side of the VSS, and the purple high reference wire to the other side, that should be a workable solution. The brown wire from the computer is called a DRAC/VSS. So connecting directly to the VSS should not hurt it, and should work. Or not.....

GPster · February 21, 2017, 04:12:50 PM

I'll have to look at my wiring diagrams and see if I can tell what the VSS on my GMC S15 donor vehicle does. There is one in my mess of wiring and maybe I can use it to run the fan that's on my radiator. I've been checking people's junk piles to find a "cut down" fiberglass fan to mount on my water pump pulley. There wasn't any accessory fans on the radiator in the truck so maybe it has something to do with the "lock-up" of the transmission's torque converter. It's part of the cable driven speedometer in the dash. I keep learning. GPster

GPster · February 21, 2017, 05:56:51 PM

Well, I just went out and started checking. What I have is not a VSS , it's a speed sensor. I can't really check it all because my instrument panel is at a shop that's trying to fix the printed circuit board. Trying to piece it together with what's here it basically has to do with a cruise control and the convience center and an over speed alarm . I thought I had eliminated all of that extra garbage but I guess because it wouldn't un-plug I must have thought it was important. None of it goes to the ECM but I quess it would have when that talk started with 5V. Maybe it's something else I can forget. GPster

sirstude · February 22, 2017, 11:19:41 AM

Thanks guys, I have to chew on this for a while, but I think this all makes sense now.

Doug

kb426 · February 22, 2017, 11:33:52 AM

I read through some of the instructions. I see several forms of adjustments. The 2 pots for on and off temps, the manual toggle switch which determines the mode it's in and the red push button that you use to program when the vss becomes effective. By connecting one side of the vss to ground and connecting the other to the numbered terminal, this looks fairly simple. I see that the control module is programmable just like the electric speedos. The control module is replacing an ecu controlled fan in this case. Same functions but a stand alone unit. At least that's what it appears to this blind old guy.

GPster · February 23, 2017, 02:47:52 PM

Well I was working from the component index on the wiring diagrams and a VSS was not listed. I found it in the wiring diagram and it was misleading because the wire colors are not the same as the piece on the back of the speedometer. The color changes where it plugs into a fixture in the wiring harness but the wiring diagram shows the VSS wired direct with out any fixture. It does show one of the wires going to the ECM but VSS is printed sideways so VSS looked like SSA to me. This goes into my diary so I don't make this mistake again. Luckily I hadn't cut all the wires out thinking it was for a cruise control. GPster