'72 Brake warning Light

O

ojh

Member
Can anybody explain how it works? I can't find a ground anywhere in the system and the schematics are 'vague'. I am working on a '72 1010 Travelall.
Does the system get a ground from the voltage regulator? Is that how it works? And when the engine starts the ground at he regulator disappears when the altenator puts out voltage?
Thanks, oj
 
Circuit 44 is designated for brake failure warning. It is comprised of 3 wires: 44, 44a & 44b. Wire 44 is 18ga and runs from a terminal of the ignition switch to the gang plug attached to the rear of the speedo cluster. 44a is also 18ga and also runs from the same ig sw terminal to a different post in the speedo gang plug. Obviously one is for bulb pos and one is for bulb neg. #44b 18ga runs from a different ig sw terminal, penetrates the firewall thru a bhc, terminating at the brake failure warning (pressure) switch. Apparently, the warning light receives ground to complete the circuit via the ignition switch, which is somehow cancelled once the engine takes off. Ground to complete the circuit and illuminate the bulb once the engine is running can only be supplied via the warning switch.
 
I figured it out. I took the ignition switch out and 'rang' out the pins to see what did what. There is one pin that is connected to the ignition shell when switch is in 'start' position and that is how it gets ground. I connected the wire that comes from warning switch and goes to the gage panel to the right pin on the switch and it works fine!
Others have been in there before me and the dwgs are so poor I couldn't solve the problem until pulling the wires off and actually checking each pin.
 
scoutboy74 said:
circuit 44 is designated for brake failure warning. It is comprised of 3 wires: 44, 44a & 44b. Wire 44 is 18ga and runs from a terminal of the ignition switch to the gang plug attached to the rear of the speedo cluster. 44a is also 18ga and also runs from the same ig sw terminal to a different post in the speedo gang plug. Obviously one is for bulb pos and one is for bulb neg. #44b 18ga runs from a different ig sw terminal, penetrates the firewall thru a bhc, terminating at the brake failure warning (pressure) switch. Apparently, the warning light receives ground to complete the circuit via the ignition switch, which is somehow cancelled once the engine takes off. Ground to complete the circuit and illuminate the bulb once the engine is running can only be supplied via the warning switch.
Click to expand...

Thanks scoutboy. Who would've figure our posts were posted at identical times! Incredible!
The dwgs from IH are incomplete and vague. The wireing on this truck has been 'fixed' and 'improved' a few times over the years and the warning light connector was moved to the wrong pin. It would have been a simpler fix except that 2 different brake controllers have been added (and they share some of the same circuitry) and an electric choke feed was included into the warning light ciruitry.
Now I have to delete some wires from an 8 trackplayer and one of those 'fm' converters that operate on a piece of the 'am' band and whoi knows, maybe things will start to work right.
Thanks again, oj
 
You're welcome. My following remarks are only in regards to the ihc factory service manuals available through the ll vendors. I won't even waste my keystrokes discussing the shitloins and haynes underwear offerings, other than to say that if one of those is your reference, then I see your point. Yes, the diagrams are a bit cumbersome, as they were originally intended for consumption only by ihc trained techs. 40 years later they are the best and really only true reference we have available to us. I've found them to be quite useful in my own electrical adventures over the years. They do take some getting used to and careful studying, but I'd hate to think where we would be if that resource were not available.
 
I'm fortunate to have the 'truck service manual, Travelall' from IH and it is easily 2" thick with a lifetimes' information in it. The carb section alone is priceless.
Unfortunatly International regarded 'electrical' as an intrusion on thier mechanical world - they never did get it right (either on paper or in practice). Its' as if they just bought a mess of leftover cables and connectors from GM and connected things just however by daisychaining. No point in utting any of that on paper because then they'd have to do all of them the same.
The very scarry part is that the wireing on these things make sense to me.
 
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