IVR pulse at 4 volts gauges read low

I restored a 69 Barracuda several years ago and ran into LOTS of electrical problems including instrument problems; to include the IVR problem. I did a TON of research and learned a lot. I can tell you that the current pulse coming from your IVR should be about 5 volts, so at 4 volts your instruments will run low. I assume you know that the IVR in your car is built into your Gas gauge. That is why the gas gauge has three terminal on the back, and the Temp and Oil Pressure only have two. The Alternator gauge has two terminals also, but is not on the gas, oil, temp circuit. I can go into great detail on how the Gas, Oils and Temp circuit works and how to test your gauges, if you would like. I would highly recommend D&M restoration to either repair the IVR in your gas gauge or to help you with a digital IVR upgrade. You can call them and they will be glad to talk to you about it. If you want my rather lengthy iteration on the gauges, let me know. http://dandmrestoration.com/