• From: Ontario, Canada
  • Registered: 2005-06-11
  • Posts: 266

Topic: Suggested amp rating of inline fuse between battery and starter?

Whats an acceptable amperage for a starter to be drawing?  I'd like to put a fuse into my start-up wiring rig so that I don't run into (any more) issues.

I slightly blew up some stuff tonight... lots of melted wires...  I'm quite frustrated, since everything seemed to be wired fine.  I'm curious if its possible that one of the 10 gauge wires (battery + to starter) heated up too much and melted to a ground wire, or if perhaps the proximity to a ground wire (ie: the outer insulation touching together?) was enough to cause a short? (how is that even possible?!)

I'm really confused.  I sat and poured over the melted wires for quite a while and I still can't see what exactly went wrong.  The insulation on one of the positive wires was melted off for about a foot and stuck to one of the ground wires.  I can only think that I carelessly placed positive and ground wires in close proximity (running along side each other) and the sheilding/insulation...somehow... wasn't enough to stop an arc. 

I thought my battery was dying because I was only getting a few cranks after charging it for about two hours but something was obviously causing a short.  The handheld rig seems to be fine and I didn't get any shocks.  I don't think it was actually a logical or schematic issue as much as carelessness and not keeping the ground wires and positive wires far enough apart... I just can't fathom how they could possibly get hot enough after about 5 seconds of cranking to melt any of the insulation?

The fire seemed to start at the battery positive post and quickly spread from there, but I think that's just an indication that there was a short SOMEwhere (which could have been after the wires melted together away from the battery)

Anyway.. I got lucky: the wires were so badly burnt that a quick tug on them ripped the ground wire apart and the fire sputtered out.  I'm going to get a fire extinguisher... but I also want to get a couple of fuses into the equation so that I don't have to worry about grabbing melting wires to stop a potential battery explosion smile

At this point, I didn't even have the alternator attached, so hopefully its ok.  I'm curious if my starter/solenoid are in good health... *sigh*    I feel like such a newb (Again... as always) and I still don't really know what I did wrong.  I'm a little hesitant to try again...


So... In future...  what size of fuse should I use between the battery + and starter?   And for more precaution, perhaps I should put a fuse between battery + and the ignition switch (the hand-held rig)  but again, how big of a fuse?

Of course, all of this, just after I recommend that someone else on this forum get the BugMe DVD and learn how to build his own engine.  He should reconsider my advice wink 

... Building engines is easy... its figuring out how to START them that has become the problem.  I used to just put a key into a thing and turn... but now....!?

-biggie

thebignic's Website

  • From: B.C.Canada
  • Registered: 2005-01-26
  • Posts: 2,610

Re: Suggested amp rating of inline fuse between battery and starter?

One shortfall of the Beetle is the #30 wire which runs all over the place unfused. I put a 40 amp breaker inline near the regulator in the wire from the regulator to the dash.

I've never heard of using a fuse or breaker in the heavy wire from the battery to the starter. Not much to go wrong in that short distance as long as the insulation is good and the grommet is there. The Bentley manual has a table of the starter currant draw under no load and load. About 200 amps under load. The solenoid alone draws 30 amps.

You could use starter relay. That way you don't run high amps all the way to and through the ignition switch.

Wires won't short through insulation as long as it's intact. Not 12 volts anyway.

From Speedy Jim's

http://www.nls.net/mp/volks/schem/starter4.gif

jim

'71 SB(DD only 79K(now 84K miles) & '78 FI Westy (project)
PO of '65 Beetle in '69, '70 Crewcab & '70 Ghia in '77
'71 Super inside rear vents now available
http://www.openroad.ca/volkswebbin/view … p?id=85915
  • From: Ontario, Canada
  • Registered: 2005-06-11
  • Posts: 266

Re: Suggested amp rating of inline fuse between battery and starter?

I'm at a total loss as to what happened then, since only the wires between starter and battery had any sort of damage.  And they were 10 gauge.  The 18 gauge wire I used for the ignition switches was undamaged and never heated up.  Not to mention that my hand was on it and I never felt anything.

I realize that not much can go wrong between the battery and the starter, but all signs point there.  The wire was brand new... I did try to crank the engine several times and the battery would always die before I could get anywhere, but it was enough to warm up the starter wires... I wonder if the insulation could have cracked after being warmed and cooled over and over...

I'm going to try and rewire everything with an actual ground strap and a very large/thick gauge positive wire for the starter.  I'm going to put an inline fuse to the ignition switch also (as per Speedy Jim's) to prevent any potential damage there.

Thanks jim

-biggie

thebignic's Website

  • From: B.C.Canada
  • Registered: 2005-01-26
  • Posts: 2,610

Re: Suggested amp rating of inline fuse between battery and starter?

The schematic says 25 mm2 wire which is 3 or 4 AWG. That may explain the heat!

jim

'71 SB(DD only 79K(now 84K miles) & '78 FI Westy (project)
PO of '65 Beetle in '69, '70 Crewcab & '70 Ghia in '77
'71 Super inside rear vents now available
http://www.openroad.ca/volkswebbin/view … p?id=85915
  • Registered: 2007-03-09
  • Posts: 40

Re: Suggested amp rating of inline fuse between battery and starter?

thebignic wrote:

I'm at a total loss as to what happened then, since only the wires between starter and battery had any sort of damage.  And they were 10 gauge.

did you have a 4 gauge wire to the solenoid from the battery also?

i am wondering if the starter solenoid might have stuck open and this fried the wire. if it was 4 gauge it would just get hot, if it was 10 gauge i think it could cook the insulation off the wire.

scott lyons
http://www.germansupply.com

Aircooled VW Online Parts Source
  • From: Ontario, Canada
  • Registered: 2005-06-11
  • Posts: 266

Re: Suggested amp rating of inline fuse between battery and starter?

Was 10 gauge to starter/solenoid from battery.  I probably should have researched that a bit more and erred on the side of caution rather than using what was available.

The new setup has proper gauge wires (replacement ground strap and positive wires for my bug) but I'm still only using 10 gauge from the alternator (B+) to the battery.  I've also put a fuse in between the ignition and battery +.

Also when wiring up the new setup, I discovered that the lower mounting bolt for the starter wouldn't stay in because the threads in the urethane starter mount were stripped.  Its funny because I had been worried about them stripping from day one, so I was very careful NOT to overtighten that bolt.  Either I didnt tighten it enough, or i still managed to overtighten it... either way, it seems to have worked its way out enough to just trash the urethane threads. 

So... by the last time I tried it (before the fire) the starter was sitting slightly askew and the gears were locking up, giving me the appearance that the battery did not have enough juice any more. It simply would not turn over after a few cranks.

Once the new wires were in place and everything was hooked back up, I put my foot on top of the starter to keep it level, and it cranked over like a dream.  I'm going to have to modify the urethane starter mount to accept a bolt through it on the bottom mount since the threads are useless now, but at least I've found out what caused the motor to stop. 

It was still my own fault that I kept my finger on the trigger while trying to turn the flywheel by hand, because I was essentially shorting out everything and potentially burning out the starter.  Thankfully, it was OK. 

So, two lessons learned:

     1) Use the correct gauge of wire and

     2) Don't keep juice going to the starter if its obviously not cranking!

Anyway...

Engine runs like a dream.  Slight oil leak from the oil cooler (not sure why - have to investigate) but no leaks anywhere else.  My vacuum cap on the carb seems to have fallen off, so its sucking a bit of air through the port, and the timing isn't set quite correctly, but it now starts up without a fuss, and doesn't seem to backfire.  I'm going to purchase a timing light and get it timed correctly at speed and tune up the carb... slap some finishing tin on it and it'll be good to go. 

Doesn't have as much bark as my 1776, but she sure sounds smooth and throaty smile

-biggie

thebignic's Website

  • From: Portage, Indiana
  • Registered: 2004-03-27
  • Posts: 454

Re: Suggested amp rating of inline fuse between battery and starter?

What is this urethane starter mount you speak of? Something you made to bench start the motor without a trans?

  • From: Ontario, Canada
  • Registered: 2005-06-11
  • Posts: 266

Re: Suggested amp rating of inline fuse between battery and starter?

It's from a kit sold by Aircooled.net

http://www.aircooled.net/new-bin/viewpr … d2=TZE0100

I don't really reccomend it, at this point, but haven't found any other vendors who carry anything similar.  The image is a bit misleading, since it looks like it might be aluminum or even steel - doesn't mention that its urethane.  It'll need modification if you want to use it more than once or twice.  Check what I've mentioned above about running your own bolt through the bottom starter mount hole since the threads will not last after repeated use.

-biggie

thebignic's Website

  • From: B.C.Canada
  • Registered: 2005-01-26
  • Posts: 2,610

Re: Suggested amp rating of inline fuse between battery and starter?

Remember you need an air cleaner in place to do the timing. I didn't realize you could start a VW engine on the floor. I'm going to do this with a type 4 engine in the spring. It would be great to check it out before putting it back in.

I do know a VW engine runs well upside down.

jim

'71 SB(DD only 79K(now 84K miles) & '78 FI Westy (project)
PO of '65 Beetle in '69, '70 Crewcab & '70 Ghia in '77
'71 Super inside rear vents now available
http://www.openroad.ca/volkswebbin/view … p?id=85915
  • From: Ontario, Canada
  • Registered: 2005-06-11
  • Posts: 266

Re: Suggested amp rating of inline fuse between battery and starter?

I think I may also need an air cleaner installed just to run the thing again, since the oil vent chute is spurting out oil without the air filter tube connected wink

-biggie

thebignic's Website

  • From: Washington, Indiana
  • Registered: 2004-03-27
  • Posts: 1,425

Re: Suggested amp rating of inline fuse between battery and starter?

Not good.......It shouldnt be doing that.....was the oil slinger installed on crank correctly?  Is it too full of oil? Did you check compression?

                                                             Yancey

Yancey's Website

  • From: Ontario, Canada
  • Registered: 2005-06-11
  • Posts: 266

Re: Suggested amp rating of inline fuse between battery and starter?

I took the oil filler off, thinking I might have put the baffles in incorrectly.  According to the Haynes manual, I have... but they appear to have put the baffles in 90 degrees rotated from the way I did, and I can't make the damn thing fit like that - apparently the baffles aren't perfectly square.  Anyway, when I took the oil filler off, I noticed that there was quite a pool of clean oil just sitting in the filler "spout" (that the cap attaches to) and it was being splashed out from the pressure inside the case. 

I emptied it out, and it hasn't sprayed anything since.  But I'm wondering if this is going to be a problem the next time I fill it with oil, since it will collect in the same spot and eventually spray that oil up into the air cleaner.  I know the air cleaner needs a bit of oil if its foam, but I don't want to overdo it...

Anyway... I'm posting a new thread about my carb tuning problems ... smile

-biggie

thebignic's Website

  • From: B.C.Canada
  • Registered: 2005-01-26
  • Posts: 2,610

Re: Suggested amp rating of inline fuse between battery and starter?

There shouldn't be pressure in the case. The hose from the oil filler to the air cleaner should prevent that.

jim

'71 SB(DD only 79K(now 84K miles) & '78 FI Westy (project)
PO of '65 Beetle in '69, '70 Crewcab & '70 Ghia in '77
'71 Super inside rear vents now available
http://www.openroad.ca/volkswebbin/view … p?id=85915
  • From: Ontario, Canada
  • Registered: 2005-06-11
  • Posts: 266

Re: Suggested amp rating of inline fuse between battery and starter?

jamesdagg wrote:

There shouldn't be pressure in the case. The hose from the oil filler to the air cleaner should prevent that.

Right, thats where the air is coming out and spraying past the sitting oil in the filler neck... The hose is currently off.

-biggie

thebignic's Website