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Posted By Discussion Topic: Sweet Spot -- page: 1 2     MG 01-27-2012 @ 2:21 PM reply profile send p.m. Senior Posts: 1263 Joined: Nov 2009 I've been fighting an electrical problem on my friends '37. It has the original 6V positive ground system in it. The car is plagued with horn and lighting problems. I'm confident that it's a grounding problem but the grounds I've added don't seem to resolve the dim headlights and taillights and the horn works very intermittently. The engine is grounded to the firewall and to the frame. The car has NORS wiring and the battery is new and fully charged. Is there a "sweet spot" with respect to the grounding on this car? We don't care if the added grounds are not as original. I'm contemplating soldering all connections as well. I'm thinking that a relay will resolve the the horn problem. Have any of you used a starting solenoid as a horn relay? We have several spare starter solenoids and I don't see why they would not work as a horn relays. This, as opposed to buying a new horn relay. alanwoodieman 01-27-2012 @ 4:15 PM reply profile send p.m. Senior Posts: 868 Joined: Oct 2009 the horn relay is built into the horn and if you take the rear bell of the horn you can clean and adjust the points to make it blow. The horn button grounds this relay to make the horn work-clean up under horn button and secure a good ground. Lighting problems can often time be traced to the connections in the "pot" under the steering box. Sometimes these fill with oil and yes I wound solder these connections MG 01-27-2012 @ 4:42 PM reply profile send p.m. Senior Posts: 1263 Joined: Nov 2009 alan, All things you have mentioned have been covered to no avail. Are you sure about the contacts/points under the horn bell as being a relay? MG 01-27-2012 @ 5:02 PM reply profile send p.m. Senior Posts: 1263 Joined: Nov 2009 BTW - the horn works great when I wire it directly to the battery. There's a voltage dropping resistance I'm having a hard time finding. shogun1940 01-27-2012 @ 6:49 PM reply profile send p.m. Member Posts: 464 Joined: Feb 2010 have you tried measuring the voltage drop while blowing the horn? once when its wired to the car and then with it on a bench test. horns draw a lot of current trjford8 01-27-2012 @ 8:16 PM reply profile send p.m. Senior Posts: 4242 Joined: Oct 2009 MG, run an extra ground from the engine to the frame. Also make sure that the ground go to clean metal.You may think everything is grounded, but it must be to clean metal. You said you ran some extra grounds. Where did you run them? supereal 01-27-2012 @ 8:24 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 Using an analog voltmeter, the kind with a needle, check all connections by placing the leads across them. Any reading will indicate loss. We run separate grounds to all loghts, etc, as using the body for a ground in an old car nearly always results in a problem somewhere, usually all over the vehicle. Be sure your battery cables are really for six volts. Many look thick, but have conductors that are too small. MG 01-27-2012 @ 9:02 PM reply profile send p.m. Senior Posts: 1263 Joined: Nov 2009 The battery cables are AWG 00 ( 2/0 ), new and clean. I ran a new ground from a right bank cylinder head stud to the frame rail and another from the cylinder head to the battery (+) ground bolt on the firewall using a braided cables and made sure they were bolted to shiny bare metal. Maybe I should mount a copper buss bar and run all new ground wires to it. Super, I assume you grounded all lights to the frame then, right? What gauge wire did you use, #12? alanwoodieman 01-28-2012 @ 6:47 AM reply profile send p.m. Senior Posts: 868 Joined: Oct 2009 do you know if the horn is a repro? I worked on a 36 with one original horn and one repro (which had no regulator built in) sounds like this could be the problem TomO 01-28-2012 @ 8:19 AM reply profile send p.m. Senior Posts: 7274 Joined: Oct 2009 MG. There are two easy ways to check for a poor grounding condition. 1) Connect a heavy wire such as jumper cables from the POS terminal of the battery to the ground connection on the headlight. Turn on the lights. They should be at full brightness if they are receiving full voltage. You can do the same for the horns. 2) Use a voltmeter (either digital or with a needle, as long as the engine is not running either will work). Connect the common lead to the POS battery terminal and the + lead to the grounding point. Turn on the lights, any reading is the amount of loss that you have in the ground circuit. To isolate the resistance point, move the +meter lead closer to the battery at each grounding connection. You can use the meter in the same manner to see the voltage drop in the supply side of the circuit. The 37 horns do not use a relay. The ground circuit is completed with the horn button. There should not be a voltage dropping resistor in the horn circuit. The only resistor should be in the primary ignition circuit. When you wire the horn directly to the battery, are you connecting the jumper wire to the hot side or grounded side of the horn? If you are jumpering the hot side, the wire from the starter solenoid to the horn may not be the correct gauge to carry the current. It should be a 12 gauge wire. If you are jumpering the grounded side, the problem is in the wire leading to the horn button or the grounding of the horn button. Tom

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