badmix
1/2 ton status
1984 K5 w/305cid
Thanks
Thanks
CK5
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Dumb question time - where is temp sending unit ?
- Thread starter badmix
- Start date
Probably the driver side head. Kind of between the #1 & #3 spark plugs.
and single dark - green wire flat spade with black protector hard plastic over it .
badmix
1/2 ton status
Ok thanks, got odds situation.
My truck temp gauge only reads around 160-165? Factory gauge.
Thought I might have stuck a 160 thermostat years ago..fast forward to today.,
drained radiator and replaced thermostat with 180*,, the one I had put in 15 years ago was infact 195* , crap..
So, have 180* thermostat, filled up radiator with 50/50 and now temp gauge won't come off 100 while running..but when i shut truck off, it shoots up to 155-160 ( middle line between 100 and 210)
WTH ? I didn't touch any wires and don't understand the problem
I let truck idle form1/2 hour and just took it down the road and romped on it. I can take radiator cap off, its barely warm.
So not sure what all is going on. If I've got various issues or not.
Also, how should the clutch fan be acting? I can turn it by hand but it has resistance and not free spinning.
My truck temp gauge only reads around 160-165? Factory gauge.
Thought I might have stuck a 160 thermostat years ago..fast forward to today.,
drained radiator and replaced thermostat with 180*,, the one I had put in 15 years ago was infact 195* , crap..
So, have 180* thermostat, filled up radiator with 50/50 and now temp gauge won't come off 100 while running..but when i shut truck off, it shoots up to 155-160 ( middle line between 100 and 210)
WTH ? I didn't touch any wires and don't understand the problem
I let truck idle form1/2 hour and just took it down the road and romped on it. I can take radiator cap off, its barely warm.
So not sure what all is going on. If I've got various issues or not.
Also, how should the clutch fan be acting? I can turn it by hand but it has resistance and not free spinning.
Need to confirm the guage is/is not reading correctly. Temp gauge will probably show a rise when engine shuts off due to heat sink.
clutch fan sounds like its good. When the engine is cold, the fan “slips” from the water pump drive, but still will turn. As the engine heats up, the fan becomes more of a direct drive with the water pump.
clutch fan sounds like its good. When the engine is cold, the fan “slips” from the water pump drive, but still will turn. As the engine heats up, the fan becomes more of a direct drive with the water pump.
rampage
3/4 ton status
Easy enough. Drop the sender (not wire portion) into boiling water. Gauge should say 210*.
Will need to ground the outer portion of the sender to the engine for it to read right correct?
rampage
3/4 ton status
That would make sense.
Speaking of grounds, it's possible the block isn't grounded well. The sender is going to use the ground for reference. Other thought would be instrument cluster grounds. Reason I'm thinking this is because how the gauge reads with the truck turned off.
badmix
1/2 ton status
Ok, but why would it just now not read properly after coolant change and thermostat change.
badmix
1/2 ton status
I just found this.............
"Temperature gauge troubleshooting begins with isolating the problem either to the gauge, sending unit, fuse or wiring. As with any electrical troubleshooting it is best to check all wiring connections are clean, tight and free of corrosion.
The following process must be preformed with the ignition key turned to the “on” position. The first place to start is at the temperature-sending unit. Remove the wire from the temperature-sending unit located on the engine (typically a dark green wire). Then connect the wire to a good ground. You can do this by using a jumper wire. Check the gauge, if the needle points to “Hot”, replace the sending unit. If the needle does not move, remove the same dark green wire from back of the gauge and connect a jumper from the terminal on the back of the gauge to a good ground. Check the gauge if the needle moves toward “Hot”, the wire from the gauge to the sending unit has an open or bad connection. If it does not move, connect a test light by grounding one end to a good known ground and the other end to positive side of the gauge (typically a pink wire). If it does not illuminate, ensure the gas gauge fuse is good. If the fuse is good, connect a jumper wire between the ignition switch and the positive side of the gauge. If the gauge now works, replace the defective wiring between the gauge and the ignition switch. If the test light illuminates there is 12 volts present, replace the temperature gauge"
I performed this test and the gauge shot up to 260* when i grounded the wire. So, it seems gauge is good but sending unit bad. Just odd it went bad when I replace thermostat and coolant.
"Temperature gauge troubleshooting begins with isolating the problem either to the gauge, sending unit, fuse or wiring. As with any electrical troubleshooting it is best to check all wiring connections are clean, tight and free of corrosion.
The following process must be preformed with the ignition key turned to the “on” position. The first place to start is at the temperature-sending unit. Remove the wire from the temperature-sending unit located on the engine (typically a dark green wire). Then connect the wire to a good ground. You can do this by using a jumper wire. Check the gauge, if the needle points to “Hot”, replace the sending unit. If the needle does not move, remove the same dark green wire from back of the gauge and connect a jumper from the terminal on the back of the gauge to a good ground. Check the gauge if the needle moves toward “Hot”, the wire from the gauge to the sending unit has an open or bad connection. If it does not move, connect a test light by grounding one end to a good known ground and the other end to positive side of the gauge (typically a pink wire). If it does not illuminate, ensure the gas gauge fuse is good. If the fuse is good, connect a jumper wire between the ignition switch and the positive side of the gauge. If the gauge now works, replace the defective wiring between the gauge and the ignition switch. If the test light illuminates there is 12 volts present, replace the temperature gauge"
I performed this test and the gauge shot up to 260* when i grounded the wire. So, it seems gauge is good but sending unit bad. Just odd it went bad when I replace thermostat and coolant.
badmix
1/2 ton status
Found this also....
"If you disconnect the lead from the coolant temp sensor in the engine and then use an Ohmmeter to measure the resistance between the sensor's connection point and earth on a hot engine it should read 30-50 Ohms. On a cold engine it will read ~140 Ohms"
"If you disconnect the lead from the coolant temp sensor in the engine and then use an Ohmmeter to measure the resistance between the sensor's connection point and earth on a hot engine it should read 30-50 Ohms. On a cold engine it will read ~140 Ohms"
Maybe just coincidence it does sound to me like the sensor failed. should be what you need.
88865046
badmix
1/2 ton status
Ok thanks
Grounded to the block? I'd just want to verify that the conditions are the same. Connection at the sender is good, etc.
I agree, changing coolant does seem a weird correlation, there is nothing to the sending unit to really fail. It happens, just a weird coincidence.
And with the sender wire NOT grounded, gauge goes past the cold end of the gauge?
All the factory truck gauges are 0-90 ohm edit: maybe incorrect. True for fuel gauge for sure, but I can't pull a gm manual right now to verify the other senders. Online sources say other than 0-90 ohm. Aftermarket and some other manufacturers use different values.
I agree, changing coolant does seem a weird correlation, there is nothing to the sending unit to really fail. It happens, just a weird coincidence.
And with the sender wire NOT grounded, gauge goes past the cold end of the gauge?
All the factory truck gauges are 0-90 ohm edit: maybe incorrect. True for fuel gauge for sure, but I can't pull a gm manual right now to verify the other senders. Online sources say other than 0-90 ohm. Aftermarket and some other manufacturers use different values.
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badmix
1/2 ton status
The gauge will go just barely past the 100mark but when i shut truck off it goes to 150 or so
badmix
1/2 ton status
Just picked up new sending unit, waiting on truck to cool down.
Quick question- do I need to put tape on threads or will it kill the " grounding" needed ?
Quick question- do I need to put tape on threads or will it kill the " grounding" needed ?
I'd put it in "dry" with no teflon tape as it can inhibit the ground connection..some thread sealing compunds for plumbing have copper mettalic powder in with it to prevent that,but its not really needed for this application..even if the sender weeps a little,it'll soon seal up around the threads after enough cooling system "crud" accumulates around the threads,there's always some rust and grunge in it..
badmix
1/2 ton status
Put in new unit "dry". I still have same issue.
Gauge won't move while running , turn truck off and up it goes, this time it went a lil past the middle mark 155-160ish. I disco'd wire and gauge stayed at 160. Doesnt make any sense.
I grounded the wire and it pegged the gauge ( by all accounts , this means gauge and wire is good)
I literally don't know what to fix or look for now
Gauge won't move while running , turn truck off and up it goes, this time it went a lil past the middle mark 155-160ish. I disco'd wire and gauge stayed at 160. Doesnt make any sense.
I grounded the wire and it pegged the gauge ( by all accounts , this means gauge and wire is good)
I literally don't know what to fix or look for now
Have you let it run several minutes with the radiator cap off ,until the thermostat has fully opened for awhile,before putting it on tight ?...it may be getting airbound,a bubble of air trapped in the passage for the sender perhaps..though its not a typical issue on an old school small block V8,it is much more of an issue on later engines..
Could be you got a bad thermostat that is sticking open too,its not uncommon for them to be "junk right out of the box" in recent years--you could test it by putting it in boiling water,but an easier check would be to use a thermometer to see what temp the coolant is after the engine has been run 15 minutes or so..also watching the coolant in the radiator after a cold start ,you shouldn't see much movement of the coolant until its ran long enough to open the thermostat...
If the fan clutch fails to release it may run cool too,but you'd probably notice the loud fan noise and eventually after driving it long enough the coolant should still get up to normal temperature..
Could be you got a bad thermostat that is sticking open too,its not uncommon for them to be "junk right out of the box" in recent years--you could test it by putting it in boiling water,but an easier check would be to use a thermometer to see what temp the coolant is after the engine has been run 15 minutes or so..also watching the coolant in the radiator after a cold start ,you shouldn't see much movement of the coolant until its ran long enough to open the thermostat...
If the fan clutch fails to release it may run cool too,but you'd probably notice the loud fan noise and eventually after driving it long enough the coolant should still get up to normal temperature..
