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Topic: Mystery fuse or circuit breaker  (Read 679 times) previous topic - next topic

Mystery fuse or circuit breaker

Hya all , went up to fit propshaft today and rear shocks , absolutely lashed with rain , so gave that a miss , decided to have another look at why I'm not getting power direct from ign switch to fuel solenoid as in a previous post a few weeks ago , just a quick recap, last time I checked out the ign solenoid and it appeared that there was no power reaching the solenoid from the ign switch, so today I decided to check out the ign switch itself , I managed to work out what wires did what , when I turned the key to on position , I had power coming out of the switch wire that goes to ign solenoid , but the power from the switch is not reaching the solenoid, so in my conclusion switch is fine , ign solenoid is fine because I jumped a wire from another live source , ign solenoid kicked in and engine started , so that has more or less convinced me that somewhere between the switch and solenoid there must be an inline fuse or circuit breaker somewhere nearby but it's really bugging me now cause I just can't find it, I have 5 seperate inline fuses under the dash which I have checked each one and there all ok, the main fuse panel under dash I've got power coming from each one checked with volt meter and took each one out aswell , I have checked the wiring diagrams and from what I'm reading there is a circuit breaker between switch and solenoid, tommorrow I'm going to try and remove the fuse panel box and see if there maybe a breaker underneath it or behind it that I just can't see , has anyone ever had similar problem as I, and know where it is .  Looking at the diagram , it shows that there is a breaker between switch and solenoid, this is a real mystery to me. It's not a major issue because if I cannot find it , I'm going to cut the switch wire , join a  piece of new wire to it, run it up under dash put a new inline fuse and connect to solenoid, I know this will work ,the only thing is what fuse amp rating would be best to place in-between 10 amp,. 15amp , 20 amp etc ? Thanks kev
1990 foretravel grandvilla, Oshkosh chassis
8.2ltr Detroit turbo

Re: Mystery fuse or circuit breaker

Reply #1 –
Am not aware of any fuse between the ignition switch and ignition solenoid-- at least none from the factory.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Mystery fuse or circuit breaker

Reply #2 –
IL try and find the wiring diagram and upload it , I'm sure I saw it ,  there has got to be either a fuse , circuit breaker , or maybe some kind of relay , I'm just thinking logically , if power actually coming from switch ok,  but not reaching the solenoid , then somewhere between , switch and solenoid there is a break in the circuit,  the only other explanation is if there isn't a breaker or fuse between the two points , then maybe when I connected up the old alternator wires the wrong way , could it possibly then have melted the wire and and actually put a break in it,  it's frustrating because I can see where the wires come from and where it goes , but the bit in the middle is hidden under fuse panel which I will try and remove tommorrow
1990 foretravel grandvilla, Oshkosh chassis
8.2ltr Detroit turbo

Re: Mystery fuse or circuit breaker

Reply #3 –
Remove the wire from the ignition solenoid and use an ohm meter from one end to the other to see if the wire is good.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Mystery fuse or circuit breaker

Reply #4 –
Oh yeah , that is good idea, I have an ometer  attachéd to my. Volt meter , one of those multi meter types ,. How many ohms should it read, I've never actually used the ohm meter , thanks
1990 foretravel grandvilla, Oshkosh chassis
8.2ltr Detroit turbo

Re: Mystery fuse or circuit breaker

Reply #5 –
Quote from: kevo0000 –
How many ohms should it read...
Close to zero, but you don't actually care about "how many ohms" it reads - you are just checking the continuity of the wire.

Some multimeters have a separate "audible" setting for checking continuity.  When on that setting, if you touch the two probes together, the meter will emit a tone.  If you touch the two probes to the ends of the wire, the tone will sound if the wire is intact.  No tone = broken wire (or blown fuse).
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Mystery fuse or circuit breaker

Reply #6 –
Quote from: kevo0000 –
Oh yeah , that is good idea, I have an ometer  attachéd to my. Volt meter , one of those multi meter types ,. How many ohms should it read, I've never actually used the ohm meter , thanks
Should read zero ohms.
Roland
1993 U280 4341
2010 Jeep Liberty
The Pied Pipers

Re: Mystery fuse or circuit breaker

Reply #7 –
Quote from: Chuck & Jeannie –
Close to zero, but you don't actually care about "how many ohms" it reads - you are just checking the continuity of the wire.

Some multimeters have a separate "audible" setting for checking continuity.  When on that setting, if you touch the two probes together, the meter will emit a tone.  If you touch the two probes to the ends of the wire, the tone will sound if the wire is intact.  No tone = broken wire (or blown fuse).
Oh yeah the  continuaty, I do have the audible function , I have already used that from switch to solenoid , but didn't disconnect the wire from solenoid when I tested it,  but I know as soon as I connect external source, to solenoid everything is fine, I know I can get round the problem, like I said earlier , but I do like to find the problem if it's not to akward , but if I was to run a new wire from switch then just need to know how many amp fuse to use , even if there isn't an inline fuse already , I would feel happier to insert a fuse , I don't wire up anything without a fuse , I'm a great believer in fire prevention , after having lost my first motorhome through a fire,  I have actually replied to an article dometic fridge fire or something like that , somebody else started the post probably 12 months ago now,
1990 foretravel grandvilla, Oshkosh chassis
8.2ltr Detroit turbo

Re: Mystery fuse or circuit breaker

Reply #8 –
At least the Foretravel wiring diagram for a 1993 Foretravel U240 shows NO fuse between ignition switch and ignition solenoid.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Mystery fuse or circuit breaker

Reply #9 –
Sure sounds like a break in the wire. Just my guess from all the other tests you have run.
Richard & Betty Bark & Keiko our Golden Doodle
2003 U320T 3820 PBDS
Build # 6215
MC # 16926
2016 Chevrolet Colorado 4X4 diesel

Re: Mystery fuse or circuit breaker

Reply #10 –
If it's factory wiring............. there should be a wire marker (number) on the wire at the switch and also on the end at the solenoid. These numbers should be the same, if different then it would indicate a device installed in between at the factory. As Brett mentioned, I see no need for anything (fuse or other device) to located between the ignition switch and the ign solenoid. I have heard of owners installing a hidden "theft prevention switch" between the ignition switch and the starter solenoid.

Do a continuity check and go from there........... you'll eventually find it.
Good luck!
Justin & Cathy Byrd
1995 U280 "Old Faithful"
36' Build #4673
C8.3 Cummins
Allison MD3060R 6 speed - retarder
Powertech 10KW  4cyl Kubota

Re: Mystery fuse or circuit breaker

Reply #11 –
Yeah will let you all know how I get on tommorrow , that was a good thought about an anti theft device between switch and solenoid , I think on this occasion , I will get a decent switch tommorrow , and bypass old wire ,  then I have two forms of anti theft , my scorpion alarm , and a hidden switch , thanks all and goodnight
1990 foretravel grandvilla, Oshkosh chassis
8.2ltr Detroit turbo

Re: Mystery fuse or circuit breaker

Reply #12 –
The ignition system works like this;
 The key on position triggers the run solenoid under the dash . This powers up the fuel run solenoid and  the alternator trigger wire.

 The start solenoid on the starter is a separate circuit sourced  from the key start switch . In my case, the  starter circuit power comes directly from  above  energized post,  on the under dash ,power up solenoid.
 
 The test method is to turn key on and check for volts at the fuel run solenoid and alt trigger . Mine are wired together.
 Lacking  12v ,check the solenoid called the run solenoid. In my case left side of the dash, for 12 volts on one post key off and 12volts on both post. key on .
 Lacking  12v on both post ; check the  key switch  for run power , key on.        I  f the switch powers up the little side post on the run solenoid, but no click of 12v on the opposing post , ground the solenoid body and listen for a click . No ground . no run.

 The ground post is near all of this  towards the front under the driver side dash . lots of green and often  black wires.  The ground  drops to the frame under the headlight on mine . Gets crusty.
 When you get this  run solenoid to work, you should have power at the engine  systems.

 The starter wire ( and miles of air lines )runs under the water tank . A sagging tank floor will cut this harness.

 


 Circuits running solenoids will seldom have a fuse or breaker  , due to the solenoid have a momentary high short style load . A slow blow fusable link  may be involved . I dont think that my bus has one . driving the starter circuits.

Re: Mystery fuse or circuit breaker

Reply #13 –
Quote from: FourTravelers –
If it's factory wiring............. there should be a wire marker (number) on the wire at the switch and also on the end at the solenoid. These numbers should be the same, if different then it would indicate a device installed in between at the factory. As Brett mentioned, I see no need for anything (fuse or other device) to located between the ignition switch and the ign solenoid. I have heard of owners installing a hidden "theft prevention switch" between the ignition switch and the starter solenoid.

Do a continuity check and go from there........... you'll eventually find it.
Good luck!

Y
Quote from: FourTravelers –
If it's factory wiring............. there should be a wire marker (number) on the wire at the switch and also on the end at the solenoid. These numbers should be the same, if different then it would indicate a device installed in between at the factory. As Brett mentioned, I see no need for anything (fuse or other device) to located between the ignition switch and the ign solenoid. I have heard of owners installing a hidden "theft prevention switch" between the ignition switch and the starter solenoid.

Do a continuity check and go from there........... you'll eventually find it.
Good luck!

Just been up the RV , for couple hrs , I've sorted the problem out , I've now cut the wire from switch added a new wire with a hidden switch , and all ok everything working as normal , so mutch easier and less time consuming than removing stuff from under dash , everything is working as it should now. Now can concentrate on the next job  thanks all kev
1990 foretravel grandvilla, Oshkosh chassis
8.2ltr Detroit turbo