Hello again, this might be a simple one, I've just never installed a coolant temp sensor before, and my intake has a few different ports, so I'd like to install it correctly. The wire for the sensor had broken off at some point in its life so a previous owner took the sensor out instead of just replacing the wire from what I can tell.. Any help or info would be appreciated!
Temp Sending Unit Position?
- Thread starter dwage
- Start date
Cranky1
Banned Old Stinky Fart
The plug where the USA tag is located should work....if not, someone will chime in. So long as it sees the water below the T-stat.....
Got off work today and was planning on putting the sending unit in and wiring it up. I realized that the stock style sending unit I bought is a smaller diameter than the port in the intake, I'll attach some photos for reference. I assume either I bought the wrong stock style unit or there is some sort of adapter I need to find...
69DodgeMan
Active Member
Pipe thread to pipe thread = hardware store.
Cranky1
Banned Old Stinky Fart
In the plumbing world it's called a reducing bushing or just a bushing. I've always liked to use a brass or stainless-steel bushing there.
Turns out it's harder to find the right reducing bushing in my area I guess.. I believe the temp sender I bought is a 1/8-27 NPT thread count, and I need a bushing that would adapt to a 5/8 NPT for that coolant access on the manifold, parts have been ordered, now we wait to see if they're right or not.
In the meantime, I wanted to ensure my coolant temp circuit functioned properly, as I've put the cluster back in the truck temporarily. I had to run a new orange and black wire from the firewall to the plug, and I grounded the coolant temp sensor straight to the negative terminal of the battery. I also checked continuity from the plug all the way back to the post coming off the gauge itself, and we're good there. As soon as I turn the key, the gauge sweeps all the way until its pegged. Not wanting to burn the gauge up (recently acquired NOS, and pricey), I quickly turned it off, double checked my ground and continuity in the same locations. Everything checks out. However, when I key on with a voltmeter on each gauge post, I'm getting 12 volts, and if I've researched correctly, the volt limiter attached to the coolant gauge should bring voltage down to about 5 volts. I suppose I could remove the limiter from the gauge assembly and check it right at the battery to know for sure, I just want to make sure there isn't something I'm missing.
-update: With the voltage limiter hooked up directly to the battery, if I test at the 12-volt terminal, 12 volts are seen with no issues, if I test at the 5-volt terminal, it bounces from 0, to 6,7,12 volts at random, never settling for more than half a second.
In the meantime, I wanted to ensure my coolant temp circuit functioned properly, as I've put the cluster back in the truck temporarily. I had to run a new orange and black wire from the firewall to the plug, and I grounded the coolant temp sensor straight to the negative terminal of the battery. I also checked continuity from the plug all the way back to the post coming off the gauge itself, and we're good there. As soon as I turn the key, the gauge sweeps all the way until its pegged. Not wanting to burn the gauge up (recently acquired NOS, and pricey), I quickly turned it off, double checked my ground and continuity in the same locations. Everything checks out. However, when I key on with a voltmeter on each gauge post, I'm getting 12 volts, and if I've researched correctly, the volt limiter attached to the coolant gauge should bring voltage down to about 5 volts. I suppose I could remove the limiter from the gauge assembly and check it right at the battery to know for sure, I just want to make sure there isn't something I'm missing.
-update: With the voltage limiter hooked up directly to the battery, if I test at the 12-volt terminal, 12 volts are seen with no issues, if I test at the 5-volt terminal, it bounces from 0, to 6,7,12 volts at random, never settling for more than half a second.
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Get a solid state replacement IVR and ditch the stock one. That was probably the reason you had to replace the gauge. When the stock ones go bad, most of the time they lock on to battery voltage which fries the fuel and temp gauges.
I already shelled out the cash to buy an original one off of eBay last night, but I'll take your advice as well as the IVRs you mentioned are readily available and relatively inexpensive. It looks like it would be simple to adapt one for this application, I'll keep you posted. Thanks for the info!
Just checking for confirmation, will this work for my application being a 3 amp power output?
Well, this is becoming quite the debacle. This is not a complicated circuit: 12v source to regulator- 5v off the regulator to temp gauge- 5v at temp gauge straight to temp sending unit- temp sending unit grounded back to the battery- regulator also gets grounded at the battery. I have my temp gauge out and have made this circuit myself using a 12v test battery and some alligator clips. What I have found is there no movement at all on the needle of the temp gauge even when you heat the probe of the sending unit. I've switched sending units out in the circuit, as I have two, and still have no movement. When I ground the wire at the sending unit, the gauge will sweep to hot. My stock voltage limiter (regulator) seems to be functioning properly as my test light strobes on the 5v side, which I found out is the correct way these originally came from factory.
I'm still waiting on those solid-state regulators to arrive, and I'll swap them into this test circuit, but like I said, it seems like the original one is functioning as it should. The two sending units I have both decrease in resistance when heated, and when at room temp, they sit at just above 700ohms, which I believe is normal. The temperature gauge seems to function normally, as it sweeps across when grounded and then returns back to cold afterwards, and my only options on finding an additional unit for testing is a $250 NOS piece on eBay right now or take my chances and by a used gauge cluster as a whole from between $125-$150 off eBay as well. I am weighing all my options it seems. 
If anyone sees anything I might be doing incorrectly, or if there's a step I'm forgetting please don't hesitate to tell me I'm doing something wrong lol. Clearly, I must be missing something...
I'm still waiting on those solid-state regulators to arrive, and I'll swap them into this test circuit, but like I said, it seems like the original one is functioning as it should. The two sending units I have both decrease in resistance when heated, and when at room temp, they sit at just above 700ohms, which I believe is normal. The temperature gauge seems to function normally, as it sweeps across when grounded and then returns back to cold afterwards, and my only options on finding an additional unit for testing is a $250 NOS piece on eBay right now or take my chances and by a used gauge cluster as a whole from between $125-$150 off eBay as well. I am weighing all my options it seems. 
If anyone sees anything I might be doing incorrectly, or if there's a step I'm forgetting please don't hesitate to tell me I'm doing something wrong lol. Clearly, I must be missing something...
Update- It was the factory voltage limiter!! Although I don't have the gauge reinstalled just yet, bench testing it with one of the solid-state regulators shown above seems to have solved the issue. Now once the sending unit gets heated up, the gauge follows suit. While I was waiting on parts, I color coded a picture of a circuit board to simplify what I was looking for; and to better help me understand what voltages are going where and why. Maybe someone else could find some use for it at some point.
Once I get my gauge reinstalled and the cluster back in the truck, hopefully I'll give the resolution update!
Once I get my gauge reinstalled and the cluster back in the truck, hopefully I'll give the resolution update!