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H2O temp guage

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by skyblazer, Dec 24, 2001.

  1. skyblazer

    skyblazer 1/2 ton status

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    After gettin the new engine fired up yesterday, the temp guage would go right up into the top of the scale. After some trial and error I got scientific and pulled out the sending unit. I put it in hot water to test it while it was wired to the guage. The top of the scale is at 180!!! Is my sending unit maybe the wrong one? Are there different ones beside the one that signals the light? What should the top of the scale indicate (temperature)?

    <P ID="edit"><FONT class="small">Edited by skyblazer on 12/25/01 08:53 AM.</FONT></P>
     
  2. greatwhite

    greatwhite Registered Member

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    sky, i had the same problem. i just droped a new engine in and installed a new (OEM from kragen) sending unit that tapped into the intake(the old chevy way). i fired it up and the temp gauge pegged out. my buddy had a lazer temp gauge and it read about 160 at my gauge peg and then the motor reached normal operating temp around 190. i said screw trying to figure that one out and bought a mechanical (more accurate) temp sender from auto meter and tapped into the left side of the cylinder head which is the best place to read engine temp. Now all my engine temp worries are history, for now anyways.
     
  3. skyblazer

    skyblazer 1/2 ton status

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    Hmmm, thanks for the info. I think I'll try to find a sending unit that will work because I would like to keep the stock guages. Did the Autometer guage mount up in the original location?
     
  4. Klef72K5

    Klef72K5 1/2 ton status

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    My gauge also pegs. I bought a new sending unit and I still have the same problem. I beleive the problem is the gauge. I just haven't had time to get a new one yet. Let me know if you get it fixed and what you did to fix it.

    <a target="_blank" href=http://wsphotofews.excite.com/031/rw/Jo/og/t488200.jpg>http://wsphotofews.excite.com/031/rw/Jo/og/t488200.jpg</a>
     
  5. skyblazer

    skyblazer 1/2 ton status

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    Will do, I'll be out of town for the next few days, but I'll let ya know when I get some more info.
     
  6. BluThndr71JMMY

    BluThndr71JMMY 1/2 ton status

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    A mechanic told me the newer 350 TSUs (temp sending unit) have the wrong values to mate with the old stock guages. He suggested a resistor in line (series) from the TSU-out terminal to make the ouput signal more compatible with a vintage temp indicator. Since it didn't work for me, I can't remember what Ohm value the resistor should be. I too, bought an auto meter mechanical temp guage and intend installing that in the near future. Good luck. Maybe one of the old-timers knows the real dope on this problem.
     
  7. Steve_Chin

    Steve_Chin 1/2 ton status

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    A switch for an idiot light will do wierd things to the gauge. The sender should read 350 ohms with respect to ground at 100 degrees F, and 68 ohms at 220 degrees F.

    Also, the intake manifold water crossover is a really bad place in a SBC for the temperature sender because there is very little room for it in there. Jamming one in there may short it to ground and damage the sender. The factory puts the sender in the driver's side head between cylinders #1 and #3.
     
  8. BluThndr71JMMY

    BluThndr71JMMY 1/2 ton status

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    What about a mechanical TSU-pickup for an Auto Meter guage in the thermostat housing? [350 goodwrench crate] The aluminum GM later-model thermostat housing seems to be chambered for something (?-- carb heat?) and with a couple of graduated adapters it looks like it's possible to fit the heat sender pickup capsule in there without getting in the thermostat's way.I'll post my results when I get around to it.
     
  9. skyblazer

    skyblazer 1/2 ton status

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    I tested resistance when I pulled mine last week, but didn't record the results. I believe they were very close to the numbers Steve posted. I'll try next week along with the numbers from a new TSU. As always, thanx for the help. PS, my TSU is mounted in the stock location, between 1 and 3.

    <P ID="edit"><FONT class="small">Edited by skyblazer on 12/30/01 11:20 AM.</FONT></P>
     
  10. Steve_Chin

    Steve_Chin 1/2 ton status

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    BluThndr71JMMY, the port on the thermostat housing is for a smog fitting (thermal vacuum switch). The problem with using the thermostat housing as the mounting point for the temperature sender is that it will not register any temperature change until the thermostat opens up.
     
  11. BluThndr71JMMY

    BluThndr71JMMY 1/2 ton status

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    Thanks, Dr. Chin. Sounds like it might make a good secondary temp pickup point &lt;&lt; Radiator Temp&gt;&gt; or something. If I needed that. So I guess my mech TSU ought to go in the stock location then -- aft of Cyl 1 and forward of Cyl 3. I put a mech Auto Meter Water temp guage in my pickup last year -- after the 20 y.o. Stewart /Warner gave out. The current price knocked me over, $40+. The one it replaced had cost under $10. That's inflation (and marketing). But then a mech guage is miles better than the OEM idiot light. And you do get what you pay for. On the Jimmy the stock electric water guage worked OK with a 327. When I dropped a 350 in -- the old TSU wouldn't chamber -- so I had to get a new TSU from the Chevy dealer. It fit the block but the readings were thru the roof. So, some one told me to put a 1/2 watt 100 Ohm resistor (I think?) in series out from the TSU to correct the difference. It hasn't worked so far. So I decided to go mechanical.
     
  12. Klef72K5

    Klef72K5 1/2 ton status

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    Hey Skyblazer
    I just caught on to you having the idiot light. Guess I need to pay more attention. FYI I have the mechanical gauges and mine pegs out. Here I thought I was helping you. LOL! Any ideas why Steve? Refer to my earlier post on this thread for what I have done. My sender is between 1 and 3 also.

    <a target="_blank" href=http://wsphotofews.excite.com/031/rw/Jo/og/t488200.jpg>http://wsphotofews.excite.com/031/rw/Jo/og/t488200.jpg</a>
     
  13. Steve_Chin

    Steve_Chin 1/2 ton status

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    Dunno why your gauges are pegging out unless you're bottoming the temperature bulb on the metal.
     

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