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Discussion Starter #1
I have a pretty big problem it appears. In trying to install an aftermarket temp gauge to replace an idiot light, we discovered that the truck is indeed running hot. It's a 1985 2.8, and we are not sure if it has a computer. There is a sender/sensor right behind the power steering pump on the head. We tried to hook the gauge up to that and it pegged out.


There is another by the intake and thermostat, which makes more sense.


No steam, no boiling, but hoses don't feel full even after water is added. Oil is clean. Is the second picture the correct spot to add a gauge? I'm overheating regardless, but want to make sure the reading is accurate.

Thanks in advance!
 

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Are you trying to connect to existing senders, or looking for a place to add the new sender?

You need to use the matching sender to the gauge. I find it's best to use the passage just under the thermostat (in the intake manifold), since the head usually does show over heating, due to being more of a cylinder head temp sender in that location than a coolant temp sender.
 

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Then it should read accuratly. I'm not sure of the problem you are having...
 

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Boozebag
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Did you solve the problem?
 

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overthinker extraordinar
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I just rebuilt an 85 with the 2.8L. There are actually three sending units on this bloc. The temp sending unit is the one on the top of the manifold next to the thermostat. The other two are on the front left corner and the right rear corner. Those two have to do with the EFE and the emissions stuff. If you used the one on the head(FL corner), I believe it is actually a switch, not a sending unit. It would have pegged your gauge instantly.

Hope this helps
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overthinker extraordinar
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Tried to replace the original sensor (temp light) with an electric gauge.
This will not work. The idiot light uses a simple thermal switch - on/off. The temp gauge uses a variable resistance sender or varistor. The current through the sender varies with temp. You could put a the gauge where the light is, but you would have to change the sending unit.
 

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Discussion Starter #9
Wow- thanks guys- I see you've gone to some lengths to answer my question.
My husband changed the sending unit behind the power steering pump, driver's side head (sorry, I never can remember what is left and right on an engine). He thinks he had the wrong sending unit. The gauge was meant for his off-road rig, and he's had it for a few years. The sending unit for the gauge got mixed up with a few different sending units and he just took a guess as to which one it was. The first one pegged out. He changed it to another the next day, and the truck ran at 190, steady. I took it on a three hour trip (one way) and all was well. Either the temp is correct and gauge is working, or the truck never overheated in the first place. But I think the gauge is working.
 

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Discussion Starter #10
This will not work. The idiot light uses a simple thermal switch - on/off. The temp gauge uses a variable resistance sender or varistor. The current through the sender varies with temp. You could put a the gauge where the light is, but you would have to change the sending unit.
I think I see what you are saying- the whole sending unit was replaced, not just a light for a gauge. We just put a wrong/different unit in. It didn't belong with the gauge.
 

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Just put in a new temp gauge, drive side on the block, has a green wire running to it, this will supply your actusl temp gauge on dash, if its acting strange, u will need a 13/16 socket. Then pull gage off cluster, wire brush terminals on the back of gage.
I just did this, mine was stuck at a 100 and never moved, works great now.
 
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