AirSpeed VW Community Forums

Technical => Electronics & Car Audio Forum => Topic started by: Buggytime on March 31, 2019, 12:50:01 PM

Title: VDO fuel gauge help
Post by: Buggytime on March 31, 2019, 12:50:01 PM
Hello all, I am installing an aftermarket VDO fuel gauge 301.252/39/9 12V 37/8, and I will be buying a new vdo sending unit from CIP for standard beetle 68-77.  I wanted to test the fuel gauge to see if it works first before installing it, but it's doing the opposite of what I have found online.  When I connect constant power to the '+', and the ground to the battery, the needle doesn't move, but all info I have found online says it should go to the full position.  When I ground out the 'G' sending unit signal wire, then the needle shoots up to the full position, but all info online says it should go to the empty position with the 'G' signal wire grounded.
Any help with this?
Title: Re: VDO fuel gauge help
Post by: BUSDADDY on March 31, 2019, 06:04:00 PM
Sounds like it's working properly to me, + & - are gauge power and G is to the sender. Stock senders vary the ground, empty is ~70 Ohms and full is nearly 0 Ohms.

Other systems decrease the ground towards full, but to work with a stock sender it sounds like you have the right gauge.
Title: Re: VDO fuel gauge help
Post by: Buggytime on April 25, 2019, 02:16:06 PM
Thanks Busdaddy, I received my new fuel tank sending unit and tested it out with my new gauge and it works perfectly.  I am so excited to finally have a fuel gauge instead of guessing all the time!