Coolant temp sensor - red or green?
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Tuned
Joined: Jun 2025
Posts: 371
Likes: 56
Coolant temp sensor - red or green?
For a little while now my coolant temp sensor hasn't been reading anywhere near the middle of the normal range. It starts cold and slowly climbs up to the "N" on the "Normal" label, and stays there. History on this truck is I got it in July and have been doing a lot of work to it. I changed out the gauge cluster a while back to get the optional one, and the coolant gauge was working then. I've done a few coolant flushes, and I don't remember exactly when it stopped climbing up in temp.
I think the thermocouple for my gauge is going out. Was driving home from work on Friday and noticed that the gauge was dropping from the "N" on normal all the way down to off and jumping back up again. To test out the gauge I had my son short out the wire against the block for 3 seconds while I watched the gauge (with the key on engine off and cold). Looking at RA, there are two different part numbers for a one wire thermal sensor - SW925 and SW2328. One is labeled as having a red ring and the other as a green ring. When I used my inspection mirror to look at mine, all I saw was a white ring. Is there an easy way to tell which type I need without pulling the plug and draining out the coolant?
I think the thermocouple for my gauge is going out. Was driving home from work on Friday and noticed that the gauge was dropping from the "N" on normal all the way down to off and jumping back up again. To test out the gauge I had my son short out the wire against the block for 3 seconds while I watched the gauge (with the key on engine off and cold). Looking at RA, there are two different part numbers for a one wire thermal sensor - SW925 and SW2328. One is labeled as having a red ring and the other as a green ring. When I used my inspection mirror to look at mine, all I saw was a white ring. Is there an easy way to tell which type I need without pulling the plug and draining out the coolant?
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Tuned
Joined: Jun 2025
Posts: 371
Likes: 56
I may have to block off one side of the radiator and see if it climbs up. It might be fine. I did replace the fan clutch, upgraded to the higher blade count fan, and do a thorough coolant flush. Just done too much in the past year to really way what is normal for this truck.
Mountain Pass
Joined: Aug 2019
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Do you know what thermostat you have?
Lead Driver
Joined: Jun 2021
Posts: 5,221
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For a little while now my coolant temp sensor hasn't been reading anywhere near the middle of the normal range. It starts cold and slowly climbs up to the "N" on the "Normal" label, and stays there. History on this truck is I got it in July and have been doing a lot of work to it. I changed out the gauge cluster a while back to get the optional one, and the coolant gauge was working then. I've done a few coolant flushes, and I don't remember exactly when it stopped climbing up in temp.
I think the thermocouple for my gauge is going out. Was driving home from work on Friday and noticed that the gauge was dropping from the "N" on normal all the way down to off and jumping back up again. To test out the gauge I had my son short out the wire against the block for 3 seconds while I watched the gauge (with the key on engine off and cold). Looking at RA, there are two different part numbers for a one wire thermal sensor - SW925 and SW2328. One is labeled as having a red ring and the other as a green ring. When I used my inspection mirror to look at mine, all I saw was a white ring. Is there an easy way to tell which type I need without pulling the plug and draining out the coolant?
I think the thermocouple for my gauge is going out. Was driving home from work on Friday and noticed that the gauge was dropping from the "N" on normal all the way down to off and jumping back up again. To test out the gauge I had my son short out the wire against the block for 3 seconds while I watched the gauge (with the key on engine off and cold). Looking at RA, there are two different part numbers for a one wire thermal sensor - SW925 and SW2328. One is labeled as having a red ring and the other as a green ring. When I used my inspection mirror to look at mine, all I saw was a white ring. Is there an easy way to tell which type I need without pulling the plug and draining out the coolant?
The N to L in normal is only like 20 -40 degrees max. I give that swing because of hte variation in gauges, voltags, wiring, and sensors technically can vary that amount overall
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Tuned
Joined: Jun 2025
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I couldn't see a red or green ring. Looks like a white ring to me. I haven't tried to get all that close to it.
If the engine is just running cooler now that I've fixed some of the cooling issues (like rust colored coolant, bad fan clutch, etc) and the gauge is reading correctly, then I'm fine with it. I just wasn't expecting the engine to run all that cool.
If the engine is just running cooler now that I've fixed some of the cooling issues (like rust colored coolant, bad fan clutch, etc) and the gauge is reading correctly, then I'm fine with it. I just wasn't expecting the engine to run all that cool.
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Lead Driver
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ISSUE:
Temperature Sender F1SZ-10884-A with a build date code prior to 2774 (277th day of 1994) should be purged from your inventory and returned to your facing PDC. These parts are being made obsolete because of an incorrect crimp during assembly. Installing these parts on a vehicle could result in early loss of temperature sender function.
ACTION:
Remove and return the suspect parts from your dealership's inventory. The obsolete parts should be withdrawn from your inventory and returned to your facing PDC within 30 days of this TSB.
NOTE:
USE TSB ARTICLE 93-24-8 FOR DIAGNOSIS PROCEDURE IN DETERMINING IF LOW GAUGE READINGS COULD BE ASSOCIATED WITH A TEMPERATURE SENDER CONCERN.
1.Perform 100% sort of all stock on hand.
2.Suspect stock has a build date code prior to 2774. Usable stock will have a build date code of 2774 or later.
NOTE:
DATE CODES ARE LOCATED ON THE SIDE OF THE SENDER HEX.
3.Usable stock can be returned to your inventory and released for normal sales.
4.Return suspect part (F1SZ-10884-A) to your facing PDC using the least expensive transportation.
5.If claim is processed electronically via DOES II, use return code "GB"; otherwise, complete a separate paper claim form FPS-340 using return code "J".
6.In the Remarks Section, write "Returned per TSB 95-13-2".
LIMITS
^The returns must be received within 30 days from the date of this TSB.
^Returns are restricted to the subject parts.
^The parts returned must have been purchased from FCSD in accordance with Policy and Procedure Bulletin 4000.
CREDIT
Credit for parts and prepaid freight costs will be issued.
Replacement stock is available for ordering
PART NUMBERPART NAME
F1SZ-10884-ATemperature Sender
Temperature Sender F1SZ-10884-A with a build date code prior to 2774 (277th day of 1994) should be purged from your inventory and returned to your facing PDC. These parts are being made obsolete because of an incorrect crimp during assembly. Installing these parts on a vehicle could result in early loss of temperature sender function.
ACTION:
Remove and return the suspect parts from your dealership's inventory. The obsolete parts should be withdrawn from your inventory and returned to your facing PDC within 30 days of this TSB.
NOTE:
USE TSB ARTICLE 93-24-8 FOR DIAGNOSIS PROCEDURE IN DETERMINING IF LOW GAUGE READINGS COULD BE ASSOCIATED WITH A TEMPERATURE SENDER CONCERN.
1.Perform 100% sort of all stock on hand.
2.Suspect stock has a build date code prior to 2774. Usable stock will have a build date code of 2774 or later.
NOTE:
DATE CODES ARE LOCATED ON THE SIDE OF THE SENDER HEX.
3.Usable stock can be returned to your inventory and released for normal sales.
4.Return suspect part (F1SZ-10884-A) to your facing PDC using the least expensive transportation.
5.If claim is processed electronically via DOES II, use return code "GB"; otherwise, complete a separate paper claim form FPS-340 using return code "J".
6.In the Remarks Section, write "Returned per TSB 95-13-2".
LIMITS
^The returns must be received within 30 days from the date of this TSB.
^Returns are restricted to the subject parts.
^The parts returned must have been purchased from FCSD in accordance with Policy and Procedure Bulletin 4000.
CREDIT
Credit for parts and prepaid freight costs will be issued.
Replacement stock is available for ordering
PART NUMBERPART NAME
F1SZ-10884-ATemperature Sender
Lead Driver
Joined: Jun 2021
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So you flushed the cooling system. hiow did you do it? Like how did you clean it, describe it. How about the overflow and hose.
did you do the thermostat, if you did, what did you buy? how did you install it?
did you do the thermostat, if you did, what did you buy? how did you install it?
Thread Starter
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Tuned
Joined: Jun 2025
Posts: 371
Likes: 56
Originally I flushed it by draining, filling with distilled water and prestone cooling system flush. Then normal driving for about a week or so, followed by draining, filling with distilled water again, run for around 30 minutes, drain, and repeat. Do this until almost clear water draining (around 11 times). Then filled with concentrated antifreeze until full, and top off the overflow with 50/50 mix. At that time I had a lower opening thermostat, like a 180 or so.
Then I had the head off in December for a broken exhaust manifold bolt. While it was off, I hosed down the head and ran water through until fully clean, lapped valves, dried out with compressed air, and reinstalled it. Did roughly the same procedure as above, though this time I used a 195 thermostat and didn't use the chemical flush. At first I had installed the thermostat backwards, then double checked the diagram in the service manual and flipped it back around. Didn't run the engine with it in there the other way.
Then I had the head off in December for a broken exhaust manifold bolt. While it was off, I hosed down the head and ran water through until fully clean, lapped valves, dried out with compressed air, and reinstalled it. Did roughly the same procedure as above, though this time I used a 195 thermostat and didn't use the chemical flush. At first I had installed the thermostat backwards, then double checked the diagram in the service manual and flipped it back around. Didn't run the engine with it in there the other way.