right now i have a pulsing on my test light coming from the voltage regulator going to the gas gauge. is it supposed to pulse or provide a steady voltage?
i had a thread on the resistor wire the other day that touched on this. this is a different aspect of the system that i feel can use a fresh thread to keep the information about the fuel gauge circuit well segmented for future search use.
It's a thermally activated pulse width modulated controller, that simulates a voltage regulator by clipping the voltage into measured pulses. They used a dc motor control circuit to essentially "drive" the fuel gauge. So yes, you should see a pulse. The pulse provides the "reference" voltage for the voltage adding portion of the circuit. Since this is a direct linear controller and not run through any amplifiers, it clips to a % of the voltage output from the charge system (either the battery or alternator). I am fairly certain it is supposed to clip at somewhere around 40% of the voltage on the thermal curve. I have no idea what the desired frequency is, because I can't find a solid spec sheet on the part. So the way it works is that the reference voltage pulses in a way that causes the coil of the fuel gauge to "flex" and the addition of the fuel sender voltage increases the temperature of the coil so that it drives the pointer to the desired point. The pulsing of the reference voltage serves to keep the coil within a desired operational range, and to prevent it from thermal runaway which would cause it to consistently over-read (an overcharging system will show a fuller tank than it really is as well). The idea is similar to using a hammer to drive a nail.
i had a thread on the resistor wire the other day that touched on this. this is a different aspect of the system that i feel can use a fresh thread to keep the information about the fuel gauge circuit well segmented for future search use.
great info. so it turns out the printed circuit that provides power to the regulator on this the cluster im working on is bad. this is a cluster that has been modified with the sunpro tach so just swaping to another cluster or printed circuit is not a easy thing. so the regulator uses a plug similar to a 9v battery plug. im going to just get a 9v battery plug and plug the one matching end into the regulator and pull the power supply wire out of the cluster plug and splice it. ive already tried a jumper wire in this configuration and i get fuel level. the has been a huge learning experience for the gas gauge function. thank you to all who have contributed their vast knowledge. another thread that shows why this forum is one of the best.
That should work just fine, the wires on that should be sufficiently sized to handle the job, but I would try to find a heavy duty version and not just cut one off some Chinese toy. Also, I'm just glad to be able to contribute information somewhere.
i got the 9v pig tail at radio shack. its amazing that most stuff now just uses metal tabs cast into plastic to hold a 9v battery now days.
