Passenger Head TCS Sending Unit Availability?

Discussion in 'Original Drivetrain Topic' started by bkmont, Dec 24, 2017.

  1. bkmont

    bkmont Veteran Member

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    Anybody got a line on where to buy the TCS Sending Unit that screws into the passenger side head of a 1970 Z28?
    Thanks,
    Bryan
     
  2. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    Interested and following

    It is pn 6489785

    Been watching on eBay for awhile and several aftermarket, but no GM
     
  3. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    Thanks.

    Looks servicable, but not OEM GM.

    I'm sure when I find one it will be in the 3 digits as it is also used on the 71 LS-6 corvette or something.

    I guess a question is can you tell once installed that it doesn't look GM?
     
  4. bkmont

    bkmont Veteran Member

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    Thanks! i just want to get the system back on line, so a repro will do just fine.
    I'll post a pic when I install it.
     
  5. bkmont

    bkmont Veteran Member

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    I wound up buying a Borg-Warner unit for 12.99 and the shipping is free. WT344 replaces GM 6489785.
    Bryan
     
  6. jbloake

    jbloake Veteran Member

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    Forums>Original Drivetrain Topic>
    confused , correct tcs temp sender 71 z ?
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    1. Aug 12, 2009
      [​IMG]
      MJLNew Member
      My contact at American Auto Wire says that the double terminal sending unit (two prong) is for AC with warning lights and the single terminal (one prong) is for non-AC. Although the assembly manual shows the single terminal, I have not looked in the AC section to see if the double terminal is displayed. Stay tuned.

      Mark

      Aug 12, 2009
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    2. Aug 13, 2009
      [​IMG]
      COPOVeteran Member
      Lifetime Gold Member

      From GM Parts Catalogue. See 1.150. You want the 2 prong for the pass side part # 6489600
      My photos from my carhttp://ca.geocities.com/mlvd@rogers.com/engine.htm. BTW, that's my car in post #7. That's the original sending unit and dual connector.

      [​IMG]

      Last edited: Aug 13, 2009
      Aug 13, 2009
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    3. Aug 13, 2009
      [​IMG]
      MJLNew Member
      The 1971 Assembly Manual UPC U14, Sheet 12HJ-3 shows part number 6489779 and also identifies TCS Clip part number 3961564. THe wire and switch are single terminal. Same manual UPC C60, sheet 12H-4 for RPO LS3, Air Conditioning - Front Wiring clearly shows the 2 terminal wire and switch part number 6489785. I cannot find a specific UPS for the 1971 Z-28. My original GM Parts manual for part number 6489600 does not list the 71 application, only 1970. The only reference in my parts manual for 1971 is part number 6489903. Based on all discussion, I am still confused. I have owned my 71 since 1976, but changed out the switch back in 1984 and don't have any old pictures.

      Still searching.

      Mark

      Aug 13, 2009
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    4. Aug 13, 2009
      [​IMG]
      COPOVeteran Member
      Lifetime Gold Member

      The assembly manual was not a 100% accurate. This is a quote from the GM Parts Office guys due to many updates going on with part numbers and diagrams from the engineers.

      Aug 13, 2009
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    5. Aug 13, 2009
      [​IMG]
      M21RSZ28Veteran Member
      The 1971 Camaro Assembly Manual has a few errors listed UPC 14 sheet 12HJ-3 titled "Instrument Panel Gauges - Temp Switch Jumper Wirer" for the TCS temp switch used with gauges which is causing some of this confusion

      The 6489779 TCS temp switch listed in the assembly manual under UPC U14 "Gauges" is not the correct switch used on 71 Camaro with gauges and is actually a 2 terminal TCS temp switch used on 71 Camaro without gauges while the drawing incorrectly shows a 1 terminal switch assembly which
      started this confusion

      Chevrolet Parts History Catalog dated 1-73 lists the 6489779 switch as being replaced by the 6489600 switch on 6-70

      The 1972 Camaro Assembly Manual continues to use the incorrect TCS temp switch drawing and 6499779 switch in UPC 12J sheet 3 titled
      "Temperature Switches & Tachometer Filter" with the last revision date of 7-6-71

      1971 Chevrolet Passenger Chevelle Camaro Nova parts catalog dated September 1970 lists the 6489600 as a 2 terminal TCS temp switch For
      71 All 8 cyl. except gauges

      The 1971 Chevrolet Passenger Chevelle Camaro Nova Parts Catalog dated September 1970 lists the correct temperature sending units and TCS temp switches in Gr. 1.150 Switch Assy.

      The pic below shows the lists of temperature sending units and TCS temp switches used on 1971 models but does not list 71 Camaro 350 w/ gauges in clear terms. The listing reads "71 all (8 cyl.) (exc. 400 w/ 4BC., 454) and "71 All w/ gauges (400 w/ 4BC., 454)”

      "All 8 cyl. (exc. 400 w/ 4BC., 454)" would include 350 which is hi-lighted in yellow in the pic below, but the next application "All w/ gauges (400 w/ 4BC., 454)" does not include the 350 engine under "All with gauges"

      After each switch assembly there is a numbered “Note” which will indicate Left or right bank location for each temperature sending unit or TCS temp switch which helps clarify the correct usage for each switch assembly as follows:

      6489600 . . . . . 71 All (8 cyl.) (exc.gauges) (2 terminals stamped AC-63B-257M) (Note 1)
      NOTE 1 These switches are located on the left bank of the engine with no other switch required on the right bank

      1993369 . . . . . . 71 All (8 cyl.) (exc.gauges) (stamped 369) (Note 2)
      Note 2 This switch is located on the left bank of the engine and used only when 6489785 or 6490094 switches appear in the right bank of the engine

      6489785 . . . . . . 71 All (8 cyl.) (exc. 400 w/4BC, 454) and 71 All w/gauges (400 w/ 4BC, 454) (2 terminals – stamped-63B-232M) (Note 3))
      Note 3 This switch is located on the right bank of engine and used with 1993369 or 1513462 on the left bank

      6490094 . . . . . . 71 All (400 w/ 4BC, 454) (exc. gauges) (Note 4)
      NOTE 4 This switch is located on the right bank of the engine and used with 1993369 on the left bank

      1513462 . . . . . . 71 All w/ gauges (Note 5)
      NOTE 5 This unit is located on the left bank of the engine and used only when 6489785 appears on the right bank of engine

      Now we can place the correct temperature sending switch and TCS temp switch by application for 1971 Camaros

      1971 Z28
      1971 SS 396
      1513462 - All w/ gauges - 1 terminal - temp sending switch (driver side head) (correct threaded stud) - 1/70 parts catalog
      6489785 - All w/ gauges - 2 terminals - TCS temp (pass. side head) - 1/70 parts catalog

      1971 Camaro
      (exc. gauges, exc. A/C)
      6489600 - 2 terminals - temp & TCS temp switch (driver side head) - 1/70 parts catalog
      (pass side head plugged)

      1971 Camaro
      1971 SS 396
      (exc. gauges w/ A/C )
      1993369 - 1 terminal - temp switch (driver side) - 1/70 catalog
      6489785 - 2 terminal - TCS temp switch (pass side) - 1/70 parts catalog

      1971 SS 396 Camaro
      (exc. gauges exc. A/C)
      1993369 - 1 terminal - temp switch (idiot light) (driver side) - 1/70 catalog
      6490094 - 2-terminal - TCS temp switch (pass side) - 9/70 catalog

      Above GM part numbers have changed over the years, GM has discontinued the TCS temp switches - aftermarket TCS temp switches are still available

      M21RSZ28


      [​IMG]

      Aug 13, 2009
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    Last edited: Dec 27, 2017
  7. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    jbloake, your question is I think which is correct for a 1970 or 71 Z28, specifically part number 6489785 that is listed in the AIM or 6489600 which is listed in a GM parts catalog?
    I do not have the exact answer for this, but for sure know its a two wire switch. My April build car has a two wire connector, but it is interesting in that the connector has a jumper wire from one terminal to the other and so only has one wire to the harness. Since both 6489785 and 6489600 are two wire switches, I can only surmise that the difference between the two would be at what temperature they actually switch internally. Since this is for emissions, It would seem the engineers were struggling to get the system (which itself is totally a stopgap kludge anyway) to meet emissions goals as changes seemed to be coming fast and furious. Functionally, I'm not sure why it makes a difference whether the car has U14 gauges or not. The temp sensor in the left (drivers) side head is for the temp gauge in a U14 system and for the idiot light in a non-U14 system.
    Since the switch is for emissions and more than likely the only difference is at what temp it switches, I think that either switch COULD be correct, depending on when the car was made. For my car, a 1970 Z28 I will be sourcing the 6489785 since it is a relatively early car. For a 71 it looks like it would also use this except if you had a no AC, No gauges "base" level car then it uses the 6489600 in the drivers head or the 6490094 for the big block, no gauges/no AC 71 cars (all 3 of them!).
    Confused? Me too!
    I think in reality I will probably on my car internally bypass the TCS vacuum solenoid valve so it has full vacuum advance all the time.
     
  8. bkmont

    bkmont Veteran Member

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    Nov 14, 2010
    Pensacola, Florida
    My current 70Z has a two wire terminal and so did my former 70Z. The BW unit I purchased is a two wire unit. I don't know at what temp it's calibrated for only that it is listed a replacement for GM part 6489785. It looks just like the $34 Electric Limited part. BW TCS Sending Unit.jpg

    6489785 is also the same unit used for 70-72 Corvettes according to my 1953 to 1980 GM Chassis and Body Parts Catalog.
    Bryan
     
  9. bkmont

    bkmont Veteran Member

    981
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    Nov 14, 2010
    Pensacola, Florida
    I do have another question, Should there be a two prong connector on the green wire to connect to the TCS sending unit? My green wire currently has bare female terminals.
    Thanks,
    Bryan
     

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