richmondred01 2,302 #1 Posted March 2, 2016 Looking to install a volt meter on a 312 with the magnum engine. Of course the m12 engine uses a rectifier. Any ideas how I can wire up a dash mount volt meter I have from an older unit. 1 Share this post Link to post Share on other sites
gwest_ca-(File Mod) 11,393 #2 Posted March 2, 2016 If you have a voltage regulator the M12 should have a 15 amp charging system. Find the accessory wire on the ignition switch. It should feed a fuse that supplies power to the light switch. Hook up between the fuse and the light switch. That way the voltmeter is off with the ignition switch off. Use the same gauge of wire as the light switch feed. or follow this 312-8 wiring diagram which has an hourmeter and voltmeter. Garry Share this post Link to post Share on other sites
richmondred01 2,302 #3 Posted March 2, 2016 Mine has the light switch as part of the key switch. No separate toggle switch just fir the lights. Share this post Link to post Share on other sites
gwest_ca-(File Mod) 11,393 #4 Posted March 2, 2016 What is the model number of this 312? Didn't know there was such a model without a light switch. Find a terminal on the ignition switch that has power only with the key in the run position. That is what you need to use to power a small say 3 amp fuse that powers the voltmeter. You can use 16 gauge wire. The negative voltmeter terminal is just grounded to the chassis. Garry Share this post Link to post Share on other sites
richmondred01 2,302 #5 Posted March 2, 2016 73428 serial 890025 Share this post Link to post Share on other sites
gwest_ca-(File Mod) 11,393 #6 Posted March 3, 2016 You are correct - no light switch on the 1998 312-8. I learn something new every day. Your hourmeter is powered by a pink wire that is already fused. Connect the voltmeter to that pink wire going to the hourmeter and it will work. You could ground the voltmeter by connecting to the hourmeter black wire. Here are some manuals that include a wiring diagram. All the info we have for this model http://www.wheelhorseforum.com/search/?q=73428&type=downloads_file Garry 1 Share this post Link to post Share on other sites
richmondred01 2,302 #7 Posted March 5, 2016 Big help. Thanks Share this post Link to post Share on other sites
