Electrical Engineering/Capacitor Advice?



I have an automotive question, but I think you may be the best person to ask so here goes. I am wanting to "trick" my car into thinking that there is a working bulb in the socket so that I wont get an error even though there is no bulb. I was thinking that the proper capacitor would produce a similar return voltage/amperage forcing the ECU to believe there is a bulb consuming electricity. I have no electrical engineering background as I am an architect, but I am handy with wiring/soldering and I really just need some advice as to how to accomplish this. The required bulb is an H7 halogen bulb and its specifications are:
55 watt
13.2 operating voltage
4.17 amperage draw

ANSWER: 13.2v - 4.17a = 3.17 ohms, so you could use an (approximately) 3.17 ohms resistor rated at more than 55W continuous (while operating at the highest ambient temperature) to simulate the bulb.  But that would waste a lot of power that is not being used.  Maybe a lower amount of current would also be detected as a bulb, and could also work , but while generating less heat.  For example, if half the current would work, that would be about 2A.  Then 13.2V / 2A = 6.6 ohms.  A standard resistor value is 6.8 ohms.  13.2V / 6.8 ohms = 1.94A, and 25.6W.  I would recommend trying that, so you're not generating so much wasted heat.  

A 6.8 ohms resistor at 50W is available from Digikey, for example:


The resistor power rating (e.g. 50W) should be higher than the actual power (e.g. 25.6W) so that the resistor doesn't get too hot on a hot day.  Read the specifications on the resistor: the power rating may depend on the resistor body being bolted to a metal part for heat dissipation.

Hope this helps!


---------- FOLLOW-UP ----------

QUESTION: Thanks for the advice, that is exactly what I was looking for! And sorry to bother you again, but how exactly would this set up be accomplished? I assume I cannot complete the circuit by connecting the resistor between the positive and negative wires so what is the best solution?

If it is a single filament bulb, there will be two connections going to it: one is probably the metal base and the other is a contact at the tip.  You would need to connect the two leads of the resistor to these two points.

Hope this helps!


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Dave Nyce


I have been an electronics engineer for many years. I can answer questions on analog and digital circuits and my specialty is sensors.


I am the inventor on 27 US patents, and also some foreign ones. Developed sensors for many years. Licensed private pilot (airplane and rotorcraft), have HAM radio license. I'm not an expert in computer networking.

AAAS, Certified Control Engineer, (former UL Advisor for Intrinsic Safety), Benefactor member of NRA. Life member of the following: Experimental Aircraft Assoc., US Parachute Assoc., National Trapper's Assoc., Apex Masonic Lodge #584, Scottish Rite of Raleigh, NC, Academy of Model Aeronautics, Grass Roots North Carolina, NC Rifle & Pistol Assoc. Member of the following: Aircraft Owners & Pilots Assoc., US Hang Gliding & Paragliding Assoc., Tripoli Rocketry Assoc., Apex Historical Society, The Planetary Society, USA Volleyball, Shriners of North America, York Rite Masons, National Space Society, Benevolent and Protective Order of Elks, and the Precision Aerobatics Model Pilots' Assoc.

Books: "Magnetic Displacement Sensors" section in: Measurement, Instrumentation, and Sensors Handbook, CRC Press, 1999. ISBN 0-8493-8347-1; "Magnetostrictive Sensors", "Hall Effect Position Transducers", & "Strain Gage Accelerometers" in: Instrumentation and Control, a Mechatronics Handbook, John Wiley & Sons, Inc. NYP; “Magnetic Level Gauges” chapter in: Instrument Engineers’ Handbook - Measurement & Analysis, 4’th Edition, CRC Press, 2003; Author of the book “Linear Position Sensors, Theory & Application”, John Wiley & Sons, 2004; “Electronic Transmitters”, “Linear & Angular Positioning of Machinery”, and “Inerting Systems” sections in: “Instrumentation Engineers’ Handbook – Process Control, 4’th edition, (2005); “Hazardous area classification and management”, and “HART Networks” sections in the book: “Instrumentation Engineers’ Handbook – Digital Process Networks and Software, 4’th edition, publication in 2011 Magazines: Magnetostriction-Based Linear Position Sensors, SENSORS magazine, April, 1994: Tank Gauging Advances, Fuel Technology & Management, January, 1997: Magnetostrictive Position Sensors, Measurements and Control, September, 1998; A Moment in Positioning, PTDesign, February, 1999; Magnetostrictive Position Sensors (update), Measurements & Control, September, 1999; Position Sensors for Hydraulic Cylinders, Hydraulics & Pneumatics, November, 2000; Magnetostrictive Linear Position Sensors, Fluid Power Journal, April, 1999; Sizing & Applying Magnetostrictive Linear Position Sensors, Motion Systems, Feb., 2002; Position Sensors in Medical Applications, ECN, May 15, 2002; Featured in “Level Sensors Go Floatless”, Machine Design, May 8, 2003; "Guitar Man" feature article, The Pelican Post, Oak Island Press, Oak Is., NC, Winter 2005; The LVDT: A Simple and Accurate Position Sensor, SENSORS magazine, August, 2005; "Model Airplane Day!", FLYING MODELS magazine, September, 2006; “Kids Having Fun!”, Half-A Flyer magazine, January, 2012

BSEE, MBA, Management by Objectives - Honeywell, Total Quality Management - MTS Systems Corporation, Looking Glass Management Workshop - Center for Creative Leadership, Motion Control Systems - Western Michigan University, College of Engineering, Organizational Excellence - University of Cleveland, Finance for Executives - Sloan School of Business, MIT.

Awards and Honors
Vaaler award, EDN magazine, "Inerting for Safety", 1987 Listed in Who's Who in Engineering, in the South, in the World. "Total Quality Management" medal awarded by MTS Systems Corporation 1991 "Best Sequel" award for the video production: "For Engineers Only" at the MTS national sales meeting, Las Vegas, 1998 (written and directed by David S. Nyce) Voted "Most Effective Leader" at Center for Creative Leadership: Looking Glass, Greensboro, NC 1995 Silver Award for New Technology at SENSORS EXPO, in Chicago, 2001 for SEF Liquid Level sensor MTS Circle of Innovators award, 2003 Elected Master of Masonic Lodge #584 , Apex, NC, 2005 "Gold Honour Award" for outstanding service in York Rite Masonry, by the York Rite Sovereign College of North America, August 22. 2007 Board of Directors: WaaRev Sensors, and the Apex Historical Society Maynard Pearson House Plaque hanging in the Masonic Fellowship Hall, for Outstanding Service and Dedication to Apex Masonic Lodge #584, Apex, NC

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