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Temperature Gauge/Sensor

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Htownbound

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New to forum, but couldn't find answer to this issue

I have an '89 K5 Blazer. Temperature gauge was not working and looked to be bad (Needle was hanging straight down). Tried the connector to ground trick and nothing happened. Pulled the dash apart and replaced the gauge. Gauge now goes to max when the key is on. Manually (with my finger) moved the gauge to low end (100 F). With the connector not hooked to the sensor and key on ,gauge stays at 100 so i dont think the wire is grounded out. When connected to the sensor and key on, it moves to max (260 F) so wiring is not broken. I replaced the sensor (link: https://www.amazon.com/gp/product/B000C9L7DI/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1), but still same results. I also checked the ground strap on the back of the block. Should run from the passenger side back of the block across towards driver side? Not sure what else the issue could be? Bad sensor maybe? Any help is appreciated.

Thanks
 
That listing does not fit my 1990 Blazer TBI engine, I think you have the wrong sender, Think that is for 1990-1995 v6 and V8s new body style.
 
I would say that having the same part as what was in it when you bought it, may not be a deciding factor due to the possibility of someone before you doing wierd things. If the wire pigtail is proper, and not spliced somewhere, that could help you decide which sensor.
Do you have an ohm meter? If you can test the sensor with a meter, maybe that will tell you something.
I could be possible to get the wrong one in the correct box, but apparently that should be obvious due to terminal style.
 
I wanted to revive this thread, as I've done more troubleshooting but still can't find the issue.

So far, I've replaced the gauge and the water temp sensor.
  • Checked the sensor with Ohm meter and resistance started about 3600 ohms and dropped towards zero as engine warmed
  • Checked continuity on both sensor and sensor wire to ground 1 where gauge plugs in. Continuity is good.
  • Checked continuity on ground 2 to the block. It's good.
What's throwing me off is the 12 volt connection to the gauge also has continuity to the block. I also get continuity to the block from the 12 volt connection as well as ground 2 when the ground cable to the battery is removed, and also when the fuse is removed. This tells me ground 2 (which should go to the block) and the 12 volt lead are somehow tied together and grounded.

I purchased the Haynes manual to see if the schematic could help, but it only goes to 87. Not sure if its the same for an 89? I'm going to hook the gauge via external wires tomm to make sure the new gauge is good, but not sure what else to check after that. Maybe the circuit board in the dash?

Any help is appreciated. Thanks
 
Wanted to post a final time for anyone else that runs into this issue.

I purchased a gauge from an 87 for my 89. Gauge didnt work, so I hooked the it up externally (directly to battery, sensor, block) and it still did not work correctly. The gauge was not broken, it topped out to 260 whenever the vehicle was turned on. I bought another gauge from an 88 blazer, plugged it in and it worked perfect. So if you have an 88/89/90 blazer, it has a different gauge than 79-87 models.

I heard from multiple sources that they are the same gauge or the only difference was gloss to flat paint. Even LMC truck says it's the same gauge for a 79-90. This was not the case for me. Not sure if the other gauges only work for 88-90, but the temp gauge is.
 
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