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Caman96

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I recently started a thread on this.
 

tayto

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try a temp sender from a 96-2000 truck, ac delco #213-820. recently did this on a 92.... gauge use to read 2 to 2 1/2 ticks lower before, even though PCM said 195*
 

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PlayingWithTBI

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The one wire SENSOR in the head is for the gauge in the dash. If you get the wrong SENDER/SWITCH, for a W/T with an idiot light and use it, your gauge won't move until the engine overheats.
 

name

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I recently started a thread on this.

Recently read the thread you started and came across something that was posted. My heads are iron and I am wondering if there is a different part number
( and maybe calibration ) for a sender / switch for trucks with alumin heads. ?

If so, It would not suprize me if the aftermarket parts were designed to "split the baby" between the two , I Also wonder if the senders may be different for trucks who run
dexa - cool. I say this because all of the senders I see from most autoparts stores look the same with two prongs for a one wire plug and I would not be suprized if Autozone, Advanced , O'rileys and Summit Racing get their parts all from the same chinese manufacturer .

Your thoughts...
 

name

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The one wire SENSOR in the head is for the gauge in the dash. If you get the wrong SENDER/SWITCH, for a W/T with an idiot light and use it, your gauge won't move until the engine overheats.

I do not think this is my problem because my gauge does move as the truck gets warm, it just stops rising earlier than it should.
 

packer0440

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I think that switch is the right one (although it could be bad). My 92 has an identical sender on it (1 wire pigtail) and gauge works perfectly, even though the switch itself has two pins on it.
 

Schurkey

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The temperature sending unit for the gauge works by supplying variable ground to the single wire attached to it. The resistance of the sensor decreases with increasing temperature. The hotter it gets, the more current flows through the sensor--and that single wire--and thus more current powers the gauge motor to swing the needle farther over.

Which means that any resistance in that circuit makes the gauge read lower than it should. Resistance is common in ~30-year-old wiring.



This all changes for trucks new enough to have stepper-motor gauges instead of the older "balanced-coil" gauges.
 

name

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The temperature sending unit for the gauge works by supplying variable ground to the single wire attached to it. The resistance of the sensor decreases with increasing temperature. The hotter it gets, the more current flows through the sensor--and that single wire--and thus more current powers the gauge motor to swing the needle farther over.

Which means that any resistance in that circuit makes the gauge read lower than it should. Resistance is common in ~30-year-old wiring.



Is there any ground locations that I should check that would effect this circuit , is there something grounding the dash cluster itself ?
 

name

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I took the sending unit and worked it in and out a couple of times in the head to make sure the sending unit was getting a good ground at the head and after I did this the gauge would not move. I then took the wire and grounded it to the battery to make sure the gauge itself pegged out and it did, confirming that the gauge itself was good. After that I took some electrical contact cleaner to the plug and prongs in the sending unit and it started working again, but still only gets to the same spot ( 140 ish) as before.

I did not put any sealant on the threads when I pulled it to clean it up so I know that to much sealant is not the issue, it went back into the head as it looks in the above picture. The plug and the green wire looks good until it disappears into the wire harness.

I feel like I am overlooking something simple, but I cant put my finger on it.
 

Schurkey

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How about the terminals at the bulkhead connector? Between dash and bulkhead connector?

Unlikely to be a problem...but where is the main engine ground connected? On my '88 it goes to the engine block where the fuel pump used to be mounted on the older vehicles. Wouldn't hurt to run a small jumper wire from the cylinder head that the sending unit screws into, to wherever the main engine ground is connected. If that doesn't help, remove the jumper wire.

The instrument cluster needs a ground, but not for the temp gauge. As said...it's grounded at the sending unit.

Do you have the correct sending unit?

When the dash gauge on my '88 K1500 quit going up to the usual "near 200" area, it was because the thermostat was defective. Replaced thermostat, gauge works good now.
 
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