Pushing horn while engine running stalls engine

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Big D

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In restoring my 1973 Duster, I replaced the inside wiring harness with '74 harness. I had to bypass the interlock wiring to get it to start and fix several small differences to get the engine harness to work properly at the bulkhead. But now as I drive it to tune the carb. and timing, I push on the horn and it makes an odd muffled sound. Then at idle, it dies while pushing the horn.

Replace the distributor, ECU, voltage regulator and battery as these were missing on the car when I bought it. Engine is a 360 with the original 340 pulled and put into the dart of the previous owner. I hooked the up the wire from the electric choke to a separate terminal on the fuse box, but other than that and a few minor things, it's as close to stock wiring as I can make it.

Any suggestions would be appreciated
 
this is way out on a limb but i think 74 is when they had the feature that the car would not start if the seat belts were not buckled. Is it possible that while using the 74 harness you accidently used something in this circuit that is effecting the engine while using the horn? I know it sounds weird but it's the first thing that pops into my mind...
 
Try to locate (on the internet) or (someone here may have them) wire diagrahms for the 73 and 74. I know that will help. I did some rewiring on my 67 Dart and found diagrahms.

Dave
 
It's very possible. The seatbelt interlock wiring is quite convoluted. I tried to trace down all of those specific wires to make sure they did not interfere with the normal circuits but the main problem-the seatbelt starter lock, has been disabled. In my tracing of the specific wiring for the horn, the Haynes book shows the horns connecting to the horn relay, and the horn relay connecting to the starter relay (power I'm assuming).
 
Dave - I do have wiring diagrams - One in the Haynes book, one print of the 1974 diagram, and one for the 1973 diagram. You'd think it would be easy now.
 
Should the horn relay be grounded? I have mine just sitting on the shelf underneath the dash.
 
Ha, ha. Thanks Green1. I already am in trouble. But I see more information better than little information--Even if it is bad information.
 
I know it is not easy. I found that not every wire on my harnesses matched the diagrahms. I am not an expert on electrical-could there be a short in the horn in the sheering, a wire touching metal, a grounding problem?
 
The two simple diagrams for the 1973 and 1974 do show small differences in the wiring so I had to chose one and go with that template. The Haynes book shows a lot more detail and has helped tremendously. On this issue though, the horn works great when the engine is off, and is only when it's running does pushing the horn affect the engine. Sounds like the run circuit is plugged into the horn circuit but I can't see how.
 
If you have dual horns disconnect one at a times and see if the problem goes away.
I can go into a drawn out 'splain how they wired the horns and why but first lets determine the problem not just a defective horn.
 
74 harnesses were a problem on their own . now you coupled it to a 73 . My suggestion would be to get the right harness. Let me know when you give up or you fry it if you need one
 
Check out mymopar.com- free wiring diagrams! Someone on this site told me about them. Good luck
 
Thank you Redfish for that dual horn suggestion. I did have horn problems a while back and I'll try your suggestion. On the wiring diagrams, my mind is quite boggled trying to keep all three wiring diagrams in check but I've narrowed down a system and it's working - up to now anyway. But the color coded wiring diagrams is genius! I'm doing the Amp gauge bypass now and it looks easy but I'll get back to horn later this week.
 
I had a friend have this problem on his honda with the wipers. there was a shard of metal in the harness that would ground out the coil wire when the wipers turned on.... it took FOREVER to diagnose.

BEST OF LUCK
 
It's kinda wierd allright! I had a Dodge Caravan that stalled on right hand turns only. I replaced the main battery ground and the problem dissapeared. Grounds are always where I start with electrical. You can help isolate the problem by pulling fuses one at a time to see if the problem stops.
 
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