| Author | Message | ||
| Bill Kennedy (Staugbill) (205.138.150.254)
Rating: N/A |
Both lo beams went out. Replaced lights, and both relays. Can't find any burned fuses. Checked dimmer switch. Lo beams still don't work. What am I missing? Any suggestions? Thanks. | ||
| Ross Carlisle (Ross) (216.107.197.199)
Rating: N/A |
Same thing just happened to me. I have not had time to take a look at it. I'll be watching this thread for ideas  I was leaning toward the dimmer switch. The bus has four rectangular head lights. On high beam all four come on so I know it's not the headlights. When I switch to low beam two of them should turn off and the two low beams should stay on. Instead, all four turn off. It's got to be either the dimmer switch or a relay. Ross | ||
| Doug Dickinson (Dougd470) (206.71.103.89)
Rating: N/A |
For high beams, there is a separate filament inside the bulb (that's why there are 3 pins). You can have high beams and all 4 come on and still have burned out low beams FWIW Doug D St Louis 83 MC9 | ||
| Ross Carlisle (Ross) (216.107.195.151)
Rating: N/A |
Did not know that. It is still unlikely that both would go at the same time though. Ross | ||
| John Noonan (Silvereagle) (24.136.93.174)
Rating: N/A |
It sounds like a bad ground connection. | ||
| Doug Dickinson (Dougd470) (206.71.103.89)
Rating: N/A |
Ross, It is possible that both headlights went out, but I agree that it is not something you would expect. In 24V coaches, it is also common to have the bulbs wired in series. Check for voltage across each low beam (between the low beam v+ and the ground) and see if you have voltage. If you have 24V on one light, then one filament is burned out and the bulbs are in series. If you are lacking a voltmeter, (you really should have one for basic troubleshooting) just replace one beam or bulb and see if that works. If not, replace that with the original and use the new one to change the other one out. Unless both are burned out (possible but not probable) then the lights will start working with one changeout or the other. For Bill and Ross - I still think the voltmeter is the best way to check them. You can find faults on many things that you can't see otherwise. Less than $15 at Lowes for a digital I bought recently. Bill has some troubleshooting to do that is going to require one. Good Luck | ||
| Bill Kennedy (Staugbill) (205.138.150.254)
Rating: N/A |
My problems are the same as Ross's. Same light configuration. I changed the light bulbs....relays next. | ||
| Bill Kennedy (Staugbill) (205.138.150.254)
Rating: N/A |
The headlights are the only 12V lights on this MCI. I've been checking with a volt meter at the relay terminals. I think checking at the outlets might be a good idea but, I don't expect to see any voltage. Unless both new bulbs were burned out. The dimmer switch only uses two terminals. so they simply switch the voltage on/off. Wiring diagram shows voltage to hi beams and dash 'hi beam' light. John, will check grounds and let you know. Thanks, guys | ||
| Ross Carlisle (Ross) (216.107.197.158)
Rating: N/A |
Since these lights are wired in series, if the first light in the series burns out, will the second one still work? I might take a look with a volt meter tomorrow, but since the bus is basically parked for the winter, it's not a high priority. Ross | ||
| FAST FRED (65.58.188.167) Rating: N/A |
IF there in SERIES, both bulb filaments must be intact. FAST FRED | ||
| Rick (12.251.212.175) Rating: N/A |
On my 74 MC8 there is a circuit breaker in the left front lower access. near the front upper part one for high beams and one for low my high beams would trip if left on for more than 15 seconds or so hope this helps | ||
| Ross Carlisle (Ross) (216.107.197.241)
Rating: N/A |
Now I have no headlights. I might just rewire them to the 12V house bank. I went out to see if I could find the problem and when I found that the high beams were dead also, discusted, I went on to another project. Ross | ||
| Doug Dickinson (Dougd470) (206.71.103.89)
Rating: N/A |
Sounds like a ground went. | ||
| Ross Carlisle (Ross) (216.107.197.25)
Rating: N/A |
Thats the way I'm leaning. All of the connections have some corrosion. I think maybe just cleaning everything up will do the trick. Ross | ||
| Robinsturn (205.188.209.11) Rating: N/A |
Well finally picked up my 1981 GMC rts II bus in Tennesee and started my trek to Florida. Headlights were out when we picked up bus. Put in new headlights - they went out when high beams were used to signal trucker safe to reenter lane - all of them - we were stranded all night. Next day lights worked for several hours then out again - bypassed switch - same thing happened. What should I do? | ||
| Richard Bowyer (Drivingmisslazy) (66.190.119.82)
Rating: N/A |
Sounds like an auto reset circuit breaker. My 80 Eagle had the same problem the first time I turned on the high beams. Replaced the CB cured the problem. Both hi and low beam were on the same breaker. Richard |