Sending Unit Help 1974 C10 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

waters5 · 09-23-2016, 12:44 AM

I Have a single tank on passenger side of a 1974 Chevy C10 Cheyenne Fleetside i recently updated my guages to Digital Dakota VHX. I am having issues getting my Gas gauge to work not sure if i am connected to wrong wire behind Dash or have bad sending unit. So i am at the point i am going to Run a new wire from gauges to the Sending unit while i drop the Tank i am going to Install new Sending unit as well.
The Problem I am having is trying to Pick the correct Sending unit. I see three available options to hook up lines. One Outlet, Two Outlet, Three Outlet style Sending units Unsure what one i Need for my 1974 Trying to Avoid Dropping tank just to Order sending unit if i can Avoid it.

**MikeB** · 09-23-2016, 08:01 PM

Did the old gas gauge work?

As for which sender to chose, your truck either has 1, 2, or 3 hard lines running along the frame from tank to engine compartment.

1 line = fuel pump feed only. Very unlikely.
2 lines = fuel pump feed + charcoal evap canister
3 lines = fuel pump feed + charcoal evap canister + fuel pump return line

**Gregski** · 09-24-2016, 10:30 AM

running a new wire for the fuel gauge is a great idea, you could also run a home run ground wire from the sending unit to the battery negative side obviously, lots of times a bad fuel gauge reading has to do with a bad ground on the gauge or the sending unit

having bought many wrong parts in the past, ha ha, I would recommend dropping your tank, yanking the old sending unit out, and holding it in your hand before you order, you may even get lucky and find a part number on it, you could also test it by connecting it up to the truck and moving the float with your hand and asking the wife to tell you if the gauge moves, ha ha

*gmachinz* · 09-24-2016, 11:21 PM

Is the VHX setup for a 0-90 ohm reading? That's what these OEM senders are. Over the years the float arm contact with the resistor board wears away the surface or literally fails to make contact sometimes. I've had to "gently bend" the arm so that it reads on my gauge. To test your sender out of the tank, take a multi-meter set to OHMs, then ground the black lead to the metal sender body and take the red lead and connect it to the sender stud. Now slowly move the float arm up and down-you should see your display read from 0 to about 93/94 which is normal. While doing it check to make sure the tang keeps contact with the resistance strip.

waters5 · 09-25-2016, 01:06 AM

Yes I have it setup for the GM-90ohm listed in the setup menu I just going to run a fresh power line from Guages to a new sending unit just wanted to make sure I order the correct one before dropping the tank

09-23-2016, 12:44 AM	#1
waters5 Registered User Join Date: Feb 2016 Location: antioch , ca Posts: 26	Sending Unit Help 1974 C10 I Have a single tank on passenger side of a 1974 Chevy C10 Cheyenne Fleetside i recently updated my guages to Digital Dakota VHX. I am having issues getting my Gas gauge to work not sure if i am connected to wrong wire behind Dash or have bad sending unit. So i am at the point i am going to Run a new wire from gauges to the Sending unit while i drop the Tank i am going to Install new Sending unit as well. The Problem I am having is trying to Pick the correct Sending unit. I see three available options to hook up lines. One Outlet, Two Outlet, Three Outlet style Sending units Unsure what one i Need for my 1974 Trying to Avoid Dropping tank just to Order sending unit if i can Avoid it. Attached Images

09-23-2016, 08:01 PM	#2
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,484	Re: Sending Unit Help 1974 C10 Did the old gas gauge work? As for which sender to chose, your truck either has 1, 2, or 3 hard lines running along the frame from tank to engine compartment. 1 line = fuel pump feed only. Very unlikely. 2 lines = fuel pump feed + charcoal evap canister 3 lines = fuel pump feed + charcoal evap canister + fuel pump return line __________________ Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that 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 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! Last edited by MikeB; 09-23-2016 at 08:06 PM.

09-24-2016, 10:30 AM	#3
Gregski Post Whore Join Date: Aug 2014 Location: Sacramento, CA Posts: 10,823	Re: Sending Unit Help 1974 C10 running a new wire for the fuel gauge is a great idea, you could also run a home run ground wire from the sending unit to the battery negative side obviously, lots of times a bad fuel gauge reading has to do with a bad ground on the gauge or the sending unit having bought many wrong parts in the past, ha ha, I would recommend dropping your tank, yanking the old sending unit out, and holding it in your hand before you order, you may even get lucky and find a part number on it, you could also test it by connecting it up to the truck and moving the float with your hand and asking the wife to tell you if the gauge moves, ha ha

09-24-2016, 11:21 PM	#4
gmachinz Account Suspended Join Date: Jun 2011 Location: Des Moines, IA. Posts: 4,143	Re: Sending Unit Help 1974 C10 Is the VHX setup for a 0-90 ohm reading? That's what these OEM senders are. Over the years the float arm contact with the resistor board wears away the surface or literally fails to make contact sometimes. I've had to "gently bend" the arm so that it reads on my gauge. To test your sender out of the tank, take a multi-meter set to OHMs, then ground the black lead to the metal sender body and take the red lead and connect it to the sender stud. Now slowly move the float arm up and down-you should see your display read from 0 to about 93/94 which is normal. While doing it check to make sure the tang keeps contact with the resistance strip.

09-25-2016, 01:06 AM	#5
waters5 Registered User Join Date: Feb 2016 Location: antioch , ca Posts: 26	Re: Sending Unit Help 1974 C10 Yes I have it setup for the GM-90ohm listed in the setup menu I just going to run a fresh power line from Guages to a new sending unit just wanted to make sure I order the correct one before dropping the tank



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