Diesel Coolant Temp Sending Unit

[lowrollin70gmc]

Howdy, I am “upgrading” my 84 GMC C1500 that was my grandfathers. As such, I’m trying to maintain a factory appearance, but better. To do this I am working on a new gauge cluster, to include a 4K rpm diesel tach (I have researched the requirements to add this to my 6.2) and factory temp/pressure/voltage gauges instead of idiot lights.

I have found the different sending unit for the 0-80psi oil gauge so I’m good there. However, the diesel coolant temp scale is 100-240 degrees vs the gas 100-260 and I can’t find a difference in listed sending units. Does this mean the senders are the same and the gauge itself compensates for the scale difference?
Or are parts companies screwing up their listings and there is a different sending unit for the lower temp scale?

Thanks for any help.

[kwmech]

The sender really doesn't know what engine it is in, it is just measuring temp. So theoretically you can use a 6cyl sender in a 454 if you are doing an engine swap.

[lowrollin70gmc]

I’m mainly worried about the scales for gauges being different, and if the senders are different for the 100-260 gauge vs the 100-240 gauge.

[hatzie]

The reason you can't find a difference is there isn't one. The thermistor in the sender will have the same resistance at 240° regardless of what gauge it's hooked to or what engine it's screwed into.

You're asking the wrong question. What makes a difference is the model year the gauge was manufactured for.
GM used several different senders and gauges depending on the model year of the vehicle. Each year/sender had different resistance curves.
What model year was your Medium Duty - ( C40, C50, or C60 ) tach cluster removed from?
Get the temp sender, not temp switch, for that model year medium duty truck and you should be good to go.

[lowrollin70gmc]

Originally Posted by hatzie

The reason you can't find a difference is there isn't one. The thermistor in the sender will have the same resistance at 240° regardless of what gauge it's hooked to or what engine it's screwed into.

You're asking the wrong question. What makes a difference is the model year the gauge was manufactured for.
GM used several different senders and gauges depending on the model year of the vehicle. Each year/sender had different resistance curves.
What model year was your Medium Duty - ( C40, C50, or C60 ) tach cluster removed from?

I’m actually assembling my own cluster as what I want doesn’t exist. I’m using a 90 electric speedo cluster as a base, swapping the gas oil/temp gauges with different scale light duty diesel gauges and adding the medium duty tach/fuel gauge. It’s taken some modification and work with the printed circuit, but it’ll be worth it in the end.

The oil and temp gauges are from an 85 6.2 powered C20, and that’s what I’m searching for on RockAuto, Autozone, and Napa. I was guessing that it was the same sending unit, considering the lower half of the scale is the same for both gauges. But the oil pressure sender being different had me questioning the temp sender as well.

Thanks for the insight, I’ve used the wiring diagrams in your signature many times as well.

[hatzie]

Download all seven GM Squarebody parts books from the manuals thread in my signature.

8993146 is the GM part for 82-84 CKP 1, 2, 3 Temp sender. It's 3/8"-18tpi. This sender was used on a bunch of the trucks and cars through the 1990's
Standard Motor TS76 Temp Sender application sheet says it replaces GM part numbers 8993146 & 8993164 and a few more so...

[lowrollin70gmc]

Originally Posted by hatzie

Download all seven GM Squarebody parts books from the manuals thread in my signature.

8993146 is the GM part for 82-84 CKP 1, 2, 3 Temp sender. It's 3/8"-18tpi. This sender was used on a bunch of the trucks and cars through the 1990's
Standard Motor TS76 Temp Sender application sheet says it replaces GM part numbers 8993146 & 8993164 and a few more so...

I downloaded the parts books and it looks like the diesel is the same sender as gas and the same part number listed 79-89. So, for future searches that find this thread, I'll confirm the same part, 8993146 is correct for gauges from 79-89 for diesels (5.7 and 6.2) based on the GM parts books, which also lists the 100-240 coolant temp gauge part number (8993982) for 82-90 6.2 powered trucks.

Those books are a great help, thank you for scanning them all in, that had to have taken quite a bit of time and energy.

[hatzie]

Several hours each book even with one of these...