Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Neutral safety switch question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Overkill, Mar 25, 2002.

  1. Overkill

    Overkill 1/2 ton status

    Joined:
    Jan 15, 2002
    Posts:
    284
    Likes Received:
    0
    Location:
    Orlando, Florida
    Does anyone know if the neutral safety switch and park safety swith are the same? I recently had a problem where the truck wouldn't start (via the key) and I had to jump the solonoid on the started. The starter is fine, but I think the safety switches are toast. It wouldn't turn over in park or neutral and I was wondering if they were the same switch. What would the probablility be that (if they were seperate) they would both die at the same time? Just trying to get the thing driveable again. Any help would be appreciated.
     
  2. azblazor

    azblazor 1/2 ton status Premium Member

    Joined:
    May 5, 2001
    Posts:
    1,953
    Likes Received:
    0
    Location:
    Arizona, Phoenix area
    I believe it's the same switch. Should be on the steering column under the dash.
     
  3. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

    Joined:
    Dec 14, 2001
    Posts:
    22,059
    Likes Received:
    69
    Location:
    Pleasanton, CA.
    The switch is the same for park and neutral. It is located on the steering column under the dash near the firewall. You could simply splice the wires together and bypass the switch if you wanted too. This could also be another little way to make your truck not start assuming that someone was trying to steal it, hook up a hidden toggle switch somewhere and run the wires to it instead and simply turn the switch off when you leave your truck. Not a bad idea and definately doesn't cost much to do for what the gain could be. Just my $.02
     
  4. Overkill

    Overkill 1/2 ton status

    Joined:
    Jan 15, 2002
    Posts:
    284
    Likes Received:
    0
    Location:
    Orlando, Florida
    Thank you for the info, both of you. Saved me a major headache. I will give it a shot in the morning and see how things go.
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,975
    Likes Received:
    189
    Location:
    Roy WA
    One other thing is that I believe the position of the switch can be adjusted, so it can get OUT of adjustment...did you try starting it in all gears, or in-between gears?

    IIRC, its a very simple switch, and actual failure is pretty uncommon. I think its just a flat piece of metal that rubs against another to make contact, and if it gets a little corrosion or junk on it, could stop working.
     
  6. RyansRod

    RyansRod 1/2 ton status

    Joined:
    Jun 13, 2001
    Posts:
    118
    Likes Received:
    0
    Location:
    Bay area CA. USA
    Re: Neutral safety switch question for TBI swap?

    I'm actually using this switch in my wiring project (TBI swap) there should be a green wire and a blue wire comming out of the switch I think. I'm trying to make this splice into my TBI computor to give it EGR info. Anyone done this before?
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,975
    Likes Received:
    189
    Location:
    Roy WA
    Re: Neutral safety switch question for TBI swap?

    Well, whats the computer using the EGR info for? To "turn on" EGR or what? Not really familiar with how whatever you are trying to do was done stock, so kind of hard to say if what you are trying to do will work. The neutral switch IIRC is basically an on/off proposition. Either its in park or neutral, (and thus can pass power to the starter) or it isn't. I don't see how you can use this to somehow pass along EGR info, unless you are making sure the computer knows the vehicle is in gear or not. Is that what you are trying to do?
     
  8. wheelnut46

    wheelnut46 1/2 ton status

    Joined:
    Nov 27, 2001
    Posts:
    122
    Likes Received:
    0
    Location:
    Rhode Island
    Just 2 weeks ago I had a problem with my switch. Suddenly the truck wouldnt start. The switch was just loose. I took it off, cleaned it up and reinstalled.
     
  9. azblazor

    azblazor 1/2 ton status Premium Member

    Joined:
    May 5, 2001
    Posts:
    1,953
    Likes Received:
    0
    Location:
    Arizona, Phoenix area
    Re: Neutral safety switch question for TBI swap?

    I just wired this switch for a TBI conversion into a 77 Suburban. The park/neutral switch is used to ground the park/neutral wire for Computer when the vehicle is in park/neutral.

    Here is some additional info if you're interested from a previous post:


    OK, here is what "Chevrolet TPI & TBI Engine Swapping" says:
    Regarding the P/N switch:
    Some wiring harnesses ground the Park/Neutral wire so that the ECM always thinks the vehicle is in Neutral or Park. The reason is to prevent the SES (service engine soon) or Check engine light from being turned on due to lack of a VSS signal. The service manual states: The ECM uses the P/N signal as one of the inputs to control: Idle Air control; VSS diagnostics; EGR. If the P/N wire is grounded in drive, the EGR would be inoperative , resulting in possible detonation.
    Without the P/N switch conected (grounded) the engine will run ok but engine speed may drop excessively when shifting into gear.

    Regarding the VSS:
    The VSS tells the ECM how fast the vehicle is going. Most people think the VSS is only used for for the lock-up torque convertor. The VSS is also used to control the EGR valve, the charcoal canister purge valve, the electric cooling fans, idle speed, and air/fuel ratio.
    It must be emphasized that the VSS is used to control the idle speed when the vehicle is moving. Without the VSS the vehicle may have stalling problems under certain conditions. The reason an engine not equipped with VSS may stall is because when the ECM has the signals that indicate the engine should be idling (foot off gas, vehicle moving less than 2 MPH), idle speed is closed loop ( which is not the same as the O2 sensor running closed loop) and the ECM will try to maintain a programmed idle speed. If the vehicle is moving, the ECM opens the IAC (idle air control) a programmed amount, regardless of engine speed, which is usually a position that will make the engine idle about 50-100 RPM above the programmed idle speed. Stalling can occur when the vehicle is in the over-run condition (foot off gas- engine speed above the programmed idle speed) because the ECM will try to lower the idle speed to the stationary programmed speed. The IAC may not be able to open rapidly enough to prevent the engine from stalling.
    Raising the minimum idle speed with the adjusting screw can eliminate stalling, but the engine will not run optimally without a VSS. Some Chevrolet engines are programmed to run lean under highway mode. Without VSS the ECM will not get the signals to run the engine for best fuel economy. There are a lot of other programs in the ECM which depend on the VSS.
     
  10. Overkill

    Overkill 1/2 ton status

    Joined:
    Jan 15, 2002
    Posts:
    284
    Likes Received:
    0
    Location:
    Orlando, Florida
    I found the switch this morning and did an adjustment, it now works fine again. All I had to do was cut the wires and splice em together! hehe. So much easier than pulling the switch out to clean/repair. Again, thanks for the info.
     
  11. RyansRod

    RyansRod 1/2 ton status

    Joined:
    Jun 13, 2001
    Posts:
    118
    Likes Received:
    0
    Location:
    Bay area CA. USA
    Re: Neutral safety switch question for TBI swap?

    I took the orange wire comming from the computer (my park neutral switch signal in) and spliced it into the signal wire that I belive was going to my old ECM. Hopefully this will work
     

Share This Page