I was wondering if anyone else had the same problem as me. My tail lights and clearance lights seemed to be tied together. I have developed a problem where they go on and off on their own when switch is on). If I turn them on they will stay on for a while then go off for about a minute then back on. It will do this when going down the road or siting in my driveway. It will even do it if the bus is not on (just lights on). It sounds like there is a relay clicking somewhere but we cannot find it. Any ideas before I go and rewire the whole thing. I checked what gounds I could find. I can tell when thel go out because the "stop lite" light (always on) on the dash goes out. Thanks for any help you guys might have.
John
1975 MC-8
You are tripping an auto reset circuit breaker (the clicking noise) in the rear electric panel and you must have a short circuit somewhere. Did you do anything (mods or maintenance) prior to this happening?
On mine
On the drivers side most front top access panel you will open up to find another panel that folds down. On the inside cover shows what breaker goes to what system. Find which one is for the lights and check the amp draw. It almost sounds like a short on the hot side. Mine was the hot wire going to the lic. plate light. shorting out.
FWIW
Skip
don't have the bus or manuals in front of me but I think the breakers your are tripping are in the driver's side engine compartment panel.
left side of compartment while facing in at the side of the engine
Sorry, didn't mean to confuse anyone. All MCIs up to and including the MC-7 had the taillight breaker in the rear panel. I didn't know they changed on the 8.
There are breaker in both ends (go figure) I certainly can't
Actually the back circuit will trip and the front dash will not be affected. The fact that he has dash lights being effected led me to the front
panel not the rear. But it could be the rear just as easily. A short somewhere is really what we agree on the rest is just tracing it down.
Skip
There are breaker in both ends (go figure) I certainly can't
By the circuit included
Where are the circuit breakers in this schematic? All I see are front panel terminal numbers 6/7 and 8/9, AC Junction box terminal numbers 4 and 5, rear panel Terminal numbers 6 and 7, Remote control box Horizontal terminal block terminal 5 and remote control box vertical terminal block terminal 5, as well as the actaul lights and ground connections.
the breakers for my 75 MC-8 are in the rear
Jack, that was my point I know there are breakers at both ends but the Schematic didn't show it.
From what I understand (and I am always willing to learn more) The front breakers are for the switchs etc. If there is no problem at the
switch end then the flow goes to the back breaker. It also works in reverse where if the back end breaker pops then the front wiring isn't
affected.
Just my thoughts.
Skip
I had a similar problem but only when towing. Also the rear marker and tail would go out but the front marker a head lights would not be affected.
my schematic shows the rear box....thats how I foud=nd it when I had a breaker go bad
So are we helping MedicNovo or have we totally confused him??
!. There is a short some where is about all we have established.
So for diagnosis purposes this is what I propose(help always appreciated).
Check for any visual wiring problems.
At the back box disconnect the wire from the front.
Check for resistance down stream and then upstream of + flow(no resistance then the short is in that direction)
Keep following in that direction until the short is found.
How does that sound?
Skip
Wow I ahve been working on this for a couple hours and just now checked back to find all this info! I checked the back but all I see are the terminals for tail lights, no breakers. Am I just not seeing them. Ill go out now and take a longer look. These wires are almost imposible to trace.
A quick note re Capn Ron's problem. MCI taillight breakers do not have enough spare capacity to handle all the clearance lights on a tow car if they use conventional bulbs. The breaker in the rear panel will trip and auto reset. I found this out the first time I drove an MCI at night with a tow car. A truck driver behind me told me that all my lights on the back were going on and off.
Some items that may help. The picture shows on the bottom some kind of roundish things. Those are the breakers we have been talking about. At the top are some relay switches which are used to reduce the amparage on a line.
Remember that each wire has a numbered metal tag and that number should hold through out so once you figure out what number wire goes whith which circuit it should follow through. Exceptions are when somebody has changed things.
Hope this helps
Skip
John,
I just went through this fiasco myself a few days ago except on a 4104.
It may help you to read the string "4104 Engine Shut Down" on page two.
It was very frustrating but I finally solved the problem.
Stan, that is very interesting. I have had the problem since I bought the bus in the fall. The previous owner installed a second set of lights above the original ones. I currently have 2 sets of (semi)functional lights. Maybe the second set is too much draw for the breaker. That would just be too simple. I will try disconnectiong 1 set to see if it still happens this weekend.
That is more than likely your problem. As I stated before I had a similar problem and it was because the breaker was not strong enough for the extra draw. I had to remove all of the marker lights from the trailer and had tail lights only. After a while even that was too much. I did have better luck when I pulled a trailer to Sturgis as I replaced the bulbs with 24 volt bulbs.
We had the same problem on our MC9. It turned out that a wire that powered the lights under the seats was shorting out and tripping the breaker.
Ok I guess the extra lights were just too much. I disconnected the second set of lights (turn, tail, stop) and drove around for a half hour. I had no issues. The lights would have gone off and on a dozen times in a half hour but not once since I disconnected the extra lights. Thanks everyone for the great advice. Now i just have to find better lenses and bulbs for the original bus lights. Thanks Again!
Now i just have to find better lenses and bulbs for the original bus lights.
Or, add additional breakers and wiring for the addtional Lights. jack
Or, replace everything with LEDs, just a fraction of the current.