Mystery Gauge - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**MikeB** · 03-26-2026, 05:26 PM

Thanks PJ. That's something I can use moving forward. I assume that's an 85 ohm shunt resistor? Meaning that when shunt resistance = sender resistance, the pointer should be at 50% of full scale?

**pjmoreland** · 03-26-2026, 05:30 PM

Quote:

Originally Posted by MikeB

Thanks PJ. That's something I can use moving forward. I assume that's an 85 ohm shunt resistor? Meaning that when shunt resistance = sender resistance, the pointer should be at 50% of full scale?

When the sender is at 85 Ohms (195°), the needle is not normally at 50%. It is usually just a little bit past the second mark, as shown in this photo. I start to get nervous about the temperature of the engine when the needle is pointing straight upward. I've owned five of these trucks, and that's how all of them have behaved. I've also built and tested about 20 gauge clusters, and they all behaved that way as well.

HO455 · 03-27-2026, 09:47 AM

Great information and timely too! The temp guage in the WMB has been reading low for a couple months now. It hasn't been a concern but, now summer is bearing down on us I need to look it into it just in case.

Here is some information on senders from a Corvette site that may be of some value unfortunately most of the photos are gone. I have some information from the thread downloaded but I is too large to post here.

http://forums.corvetteforum.com/c1-a...t-problem.html

03-26-2026, 05:26 PM	#1
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 4,035	Re: Mystery Gauge Thanks PJ. That's something I can use moving forward. I assume that's an 85 ohm shunt resistor? Meaning that when shunt resistance = sender resistance, the pointer should be at 50% of full scale? __________________ Mike 1969 Custom/10 LWB -- owned for 37 years. 350/TH350, 3.08 posi, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. Hedman stainless headers. Old Air installation in progress. 1982 Custom Deluxe 10 SWB -- converted from 250-six to roller cam 350 w/ Vortec heads -- sold 1981 C10 Silverado LWB, 305, TH350C -- sold, but wish I still had it! 1969 C10 (not the current one) which I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 26 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!

03-27-2026, 09:47 AM	#3
HO455 Registered User Join Date: Feb 2016 Location: Portland Oregon Posts: 12,406	Re: Mystery Gauge Great information and timely too! The temp guage in the WMB has been reading low for a couple months now. It hasn't been a concern but, now summer is bearing down on us I need to look it into it just in case. Here is some information on senders from a Corvette site that may be of some value unfortunately most of the photos are gone. I have some information from the thread downloaded but I is too large to post here. http://forums.corvetteforum.com/c1-a...t-problem.html __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 Last edited by HO455; 03-27-2026 at 10:00 AM.

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