1995 E350 Blowing Fusible Link, Vehicle Loses All Power

[gtbensley]

I have another thread going here from a while back but I have learned some information since then. I have a 1995 E350 ambulance with a 7.3 diesel with about 155,000 on the clock. Everything was fine and dandy up until a month or so ago when I was using my invertor and blew something, causing the vehicle to lose all power. Dead as can be....just like I had removed the batteries.

After some serious digging, reading, and help from the kind folks here I ended up replacing a fusible link that runs off the starter relay which can be seen in this picture (not mine but the same set up). The link I replaced is that small green one.



Once I did that and connected my batteries the problem seemed to be solved. Started and ran no problem. It was like I had installed batteries while before there were non in the vehicle.

I drove it for a couple hundred miles and lots of around town stuff to help build some confidence back in it.

A couple nights ago however I rinsed the salt off it and had it idling outside while I locked up the building. Had the parking lights on and the high idle going (it was -5 out). Hopped in the van, pulled the switch for the headlights and BAM, it just shut off. No power again. Nothing.

I cut out the fusible link I had replaced and jumped it with a wire. The vehicle powered back up and that is how it stand currently. Sitting in a parking lot but not fixed.

What does that fusible link feed that could possible be killing ALL power the vehicle? I am having trouble finding a wiring diagram that shows it. Further more, I thought I had just over loaded the inverter and caused the problem but clearly not. The only thing that was consistent between the two issues was the high idle was on in both cases.

 

[gtbensley]

From the last

 

[mgmetalworks]

If your picture is accurate, that heavy gauge red BATT+ wire is physically connected to your fuseable link correct? So when *something* inline with that fuseable link is "on", that big fat battery wire is going straight to ground thus frying your weakest link. Think about what would happen if you laid a wrench across your battery terminals... same thing going on here, the wrench in this case if your fuseable link wire taking so much load that it burns up.

Whatever is on that circuit has a short somewhere. There could be multiple things on that same circuit too so you're left with no choice but to trace that wire all the way through to each of its end points. There could be insulation worn away, it could be the item at the end of the circuit leg (bad switch, bad module, etc...). That doesn't mean you have to physically look at every inch of wire but if you could, that would be awesome. Get yourself a wiring diagram and map out all of the connections that wire has. You can troubleshoot without a manual but it would be so much faster if you knew where each of its terminations and pass-throughs were.

You're actually kind of lucky that you've burnt out that link quickly rather than put that much amperage through the harness where it could cause a much bigger problem.

 

[naterry]

E-Gremlins are a B***H!

Unfortunately (or fortunately depending on how you look at it) you are going to have get good at reading electrical diagrams and tracing and isolating the circuits in your amby. I doubt that anyone here can remotely intuit where the short in your system is.

If I was in your shoes I would hunt down the circuit that powers all of the current (and possible since removed) ambulance systems (lights, generator, vac pump, rear heater/AC, high-idle control box, etc). Once you isolate these add-ons you can use a multimeter on each and every circuit to detect a ground where it shouldn't be. This ground may be intermittent, perhaps this short is only detectable when the van is shaking at whatever frequency the high idle induces? It's anybody's guess, and could be very simple or a long term process of elimination.

Diagrams: https://www.google.com/search?q=1995+econoline+circuit+diagrams&safe=off&espv=2&biw=1745&bih=890&tbm=isch&tbo=u&source=univ&sa=X&ei=A-PsVPPxApHZoASYnoKACA&ved=0CB0QsAQ#imgdii=_&imgrc=26dqwykcPTmkQM%253A%3Bwf3UykMJxWCSXM%3Bhttp%253A%252F%252F1.bp.blogspot.com%252F--IdxmESUYRc%252FTaTx3R_ZgQI%252FAAAAAAAAADU%252F8OuXJEymDJ8%252Fs1600%252F1997-Ford-Econoline-E150-Instrument-Cluster-System-Schematic.png%3Bhttp%253A%252F%252Fowner-manual.blogspot.com%252F2011%252F04%252Finstrument-cluster-system-schematic.html%3B756%3B936

How-To's: https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=how+to+find+shorts+in+vehicle&safe=off&tbm=vid

 

[gtbensley]

Thanks. So I need to follow some wiring and look at diagrams. Am I looking for the connections that fusible link I replaced feeds? Or the other much fatter cable feeding power to the solenoid? That fusible link is a 16 gauge so it cant be holding much current right?

 

[naterry]

The fat cable should go straight to your battery or to your battery via your starter.

 

[mgmetalworks]

For starters, focus your efforts on what is connected to that green wire.

 

[gtbensley]

Will do, looking through some factory manuals right now to see what I can learn. I feel that's the only way to understand what that feeds? I can't see the wire after about six inches.

 

[Bikersmurf]

X2 on looking into what if feeds into.

You're looking for a short after the green 'link' and before any other fuses. I suspect if it were after another fuse, it would be going first (most likely).

Annother thought, was the replacement link the same rating as the one it replaced? Where I'm going with that thought is that I could easily blow a 100 amp fuse able link if I had the high idle going and the alternator was feeding 150+ amps to the batteries and accessories... The 'stock type' alternator wouldn't cause a problem, but the ambulance package 215 Amp Alternator could melt that tiny wire in 1/2 a second. (Short not required)

That said, Ambulances are carefully engineered to be reliable... Just beware of PO(s) who do silly things like, in my case, wiring the alternator directly to the house batteries (bypassing the battery isolator) and then wiring it so the isolator drains the cranking batteries to charge the house batteries (when the engine is off).

 

[IdaSHO]

Looks to be alternator or fuse panel.

If it has a fused link Id say alternator.

 

[gtbensley]

i will have to check and see what size link I replaced it with. It was pretty darn small, maybe sixteen gauge.

If it's feeding my fuse panel that would make a lot of sense, it kills the WHOLE vehicle when it blows. I'll see if I can get a specific picture of mine.

So this fater one with two feeds the fuse box?



That link is fine so according to the previous picture someone posted its a very small link running to the alternator? I'm confused as to what that link does for the alternator and how it's killing the whole vehicle.

 

[Mwilliamshs]

Seriously doubt it's a short. You're just drawing too much current. I'd pick a big accessory draw like the lighting circuit or high-idle control box and isolate with its own fused circuit, separate from that fuse link. With all the ambo addons and maybe one or two of your own plus a little age making things draw more current than they did when new, you're just exceeding the amp rating of the link. The wiring would likely burn if you up the link rating or leave the solid wire you're using now because that's the link's job, it burns before the wire.

 

[gtbensley]

I hope you are right, and you know much more then I do no doubt.

Can I change that link to a fuse while I am in there? Incase it goes again or is that a very dumb idea?

 

[gtbensley]

I also found a broken ground strap that leads in the direction of the inverter. Its located from the body to the fram directly under where the invterer is located.

 

[Mwilliamshs]

Poor grounding can up the amp draw. Fused link can be replaced by a fuse but it's not good practice. Links can operate very close to their rating for a long time. Fuses die from heat under similar conditions. Fix the ground, check the rest of them (clean and solid connections) and your problem might go away. Isolate the heavy circuit(s). I'd just do lights, even just the headlights. It's a 30 minute job to put them on their own relay and the plug-and-play kits are readily available and cheap, plus it'll make your headlight switch last basically forever and make the lights brighter. If that ~10 amps (2 55w bulbs @ 12v = 9.16a) isn't enough I'd isolate all the lights or the idle box or whatever is power hungry and used often.

Have you ever had this problem when the lights weren't turned on? Are your accessory lights on when the headlights are on? Maybe reduce the load by turning some off or switching to LEDs?