Mackman686 Posted April 4 Share Posted April 4 Hi all, I’ve got a problem on my hands. My low air buzzer is going off all the time in my 1990 Mack RB688RST nz model. I’ve replaced and now unplugged the new air pressure switches on the fire wall and the buzzer is still going off. The only way to stop it is by pulling the circuit breaker out or turn the key off. Any help would be much appreciated, photo below of the truck and the buzzer set up. Thanks again 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76547-low-air-buzzer-going-off-all-the-time/ Share on other sites More sharing options...
Popular Post Joey Mack Posted April 4 Popular Post Share Posted April 4 Isnt that a multi buzzer? It also sounds out with the turn signals, right ? And power divider if you have a locker. ? 3 Quote Link to comment https://www.bigmacktrucks.com/topic/76547-low-air-buzzer-going-off-all-the-time/#findComment-594116 Share on other sites More sharing options...
Mackman686 Posted April 4 Author Share Posted April 4 8 hours ago, Joey Mack said: Isnt that a multi buzzer? It also sounds out with the turn signals, right ? And power divider if you have a locker. ? Yeah it is a multi buzzer, low oil pressure, low water, low air, power divider, and the turn signals. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76547-low-air-buzzer-going-off-all-the-time/#findComment-594126 Share on other sites More sharing options...
Joey Mack Posted April 4 Share Posted April 4 Does it cut off if you unplug the turn signal switch, ? I am leaning towards an electrical backfeed... due to a grounding issue.. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76547-low-air-buzzer-going-off-all-the-time/#findComment-594127 Share on other sites More sharing options...
Mackman686 Posted April 4 Author Share Posted April 4 1 hour ago, Joey Mack said: Does it cut off if you unplug the turn signal switch, ? I am leaning towards an electrical backfeed... due to a grounding issue.. Nah I haven’t unplugged the turn signal, it’s brand new aswell and never had this issue until I’ve started putting everything back together in the truck. I’ll try that though cheers Quote Link to comment https://www.bigmacktrucks.com/topic/76547-low-air-buzzer-going-off-all-the-time/#findComment-594129 Share on other sites More sharing options...
Joey Mack Posted April 4 Share Posted April 4 With the pressure switches being new, do you have the normally closed and normally open switches in the right spots? But you did say with them unplugged it still sounds out.. still leaning towards a backfeed... 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76547-low-air-buzzer-going-off-all-the-time/#findComment-594133 Share on other sites More sharing options...
BottleHauler84 Posted April 5 Share Posted April 5 Does your shut down light in the dash work or come on at all or stay on? I had this same issue on my 88. Not sure if yours does, but If your truck has the Kysor shut down system, theres a sensor on the coolant manifold on the drivers side of the engine with 3 wires. Mine was located at the rear of the water manifold. Mine was corroded and shorting out. Might give it a look. Alot of people disable them so it no longer activated the light and buzzer. 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76547-low-air-buzzer-going-off-all-the-time/#findComment-594148 Share on other sites More sharing options...
Mackman686 Posted April 5 Author Share Posted April 5 4 hours ago, Joey Mack said: With the pressure switches being new, do you have the normally closed and normally open switches in the right spots? But you did say with them unplugged it still sounds out.. still leaning towards a backfeed... Yeah it’s sounds like a power back feed but will check everything that has been suggested. Thanks again!! Quote Link to comment https://www.bigmacktrucks.com/topic/76547-low-air-buzzer-going-off-all-the-time/#findComment-594154 Share on other sites More sharing options...
Mackman686 Posted April 5 Author Share Posted April 5 (edited) 2 hours ago, BottleHauler84 said: Does your shut down light in the dash work or come on at all or stay on? I had this same issue on my 88. Not sure if yours does, but If your truck has the Kysor shut down system, theres a sensor on the coolant manifold on the drivers side of the engine with 3 wires. Mine was located at the rear of the water manifold. Mine was corroded and shorting out. Might give it a look. Alot of people disable them so it no longer activated the light and buzzer. Hey there, yes it does have a kysor shutdown system in it. The shutdown light comes on then goes out when oil pressure is reached. It has these 2 senders on the water jacket, I assume the rear one is the kysor and the other is water temp. I test the wire coming from the plug for the multi alarm and when I’ve reached air pressure it still has power and when the pressure switches are unplugged just the same Edited April 5 by Mackman686 Quote Link to comment https://www.bigmacktrucks.com/topic/76547-low-air-buzzer-going-off-all-the-time/#findComment-594156 Share on other sites More sharing options...
Geoff Weeks Posted April 5 Share Posted April 5 I believe all the switches on the system are grounding switches (ground for low oil/air high water temp). so will show "power" when the switches are not grounded. At least that is how the vast majority I have seen work. Ground any one of the switches and the buzzer come on. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76547-low-air-buzzer-going-off-all-the-time/#findComment-594160 Share on other sites More sharing options...
Mackman686 Posted 3 hours ago Author Share Posted 3 hours ago (edited) Hi everyone, I thought i better give you and update on the low air buzzer going off all the time. Sooooo after pulling the dash apart and tracing wiring over the long weekend of easter for 4 days, I found the problem!! I replaced the multi buzzer as i thought my old one was buggered, it was the buzzer its self was so i soldered a new one into the board. The new multi buzzer that i got, original Mack part must have some different circuits to the old one and was back feeding power out of the board and setting the kysor and low air alarms off. So Ive attached a couple of photos of the boards the green one is the new one and the original is the cream colored one. And i got a period correct wiring diagram for the truck which has helped with a few other problem which have been sorted. Cheers Keegan Edited 3 hours ago by Mackman686 1 Quote Link to comment https://www.bigmacktrucks.com/topic/76547-low-air-buzzer-going-off-all-the-time/#findComment-594798 Share on other sites More sharing options...
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