TTA - Possible Short?

[Jan Larsson]

So got everything ready to fire up my TTA (engine rebuilt etc) and got everything connected except for front lights (connectors loose with no bulbs connected).

Connecting the positive terminal to the battery and I get a arc so typical short circuit somewhere .

Anyway with battery cables disconnected I measured (ohm) and I get a reading indicating a short circuit somewhere ..... no resistance what so ever.

Can someone confirm I should have high resistance between the positive and negative battery poles when disconnected from the battery.

I have to work backwards and disconnect stuff and see if I can find the short but just like to confirm I should have high resistance between plus and minus before I get started.

 

[garyk1970]

i tested two cars here so i can help you. heres how; hook up the ground lead to the battery,leave the positive battery lead unhooked from the battery.measure Resistance from the ground lead/battery terminal to the unhooked positive battery lead.this will show any ground/shorts to ground on the unhooked pos battery cable.

1) my 86 GP computer feed back carb with computer ; 10.5k ohms.

2) a 72 olds cutlass I'm working on, no computer,etc; 6 mg ohms

you SHOULD have 2k-15k ohms when measuring as described above. if your ohm meter shows less than 10 ohms for example,there may be a positive circuit short to ground.most cars like yours with computers,audio amps,etc with "spark" at first to charge capacitors in various componets through out the cars electrical system . a small "spark" is normal.

if you meter shows low ohms ( 0 zero is a dead short) then check the starter wiring at starter first.positive leads off the starter can spin when tightening the bolts and touch the starter housing .

post up the numbers so i can help further.

 

[Jan Larsson]

i tested two cars here so i can help you. heres how; hook up the ground lead to the battery,leave the positive battery lead unhooked from the battery.measure Resistance from the ground lead/battery terminal to the unhooked positive battery lead.this will show any ground/shorts to ground on the unhooked pos battery cable.

1) my 86 GP computer feed back carb with computer ; 10.5k ohms.

2) a 72 olds cutlass I'm working on, no computer,etc; 6 mg ohms

you SHOULD have 2k-15k ohms when measuring as described above. if your ohm meter shows less than 10 ohms for example,there may be a positive circuit short to ground.most cars like yours with computers,audio amps,etc with "spark" at first to charge capacitors in various componets through out the cars electrical system . a small "spark" is normal.

if you meter shows low ohms ( 0 zero is a dead short) then check the starter wiring at starter first.positive leads off the starter can spin when tightening the bolts and touch the starter housing .

post up the numbers so i can help further.

Thanks for confirming, much appreciated. Yes I got 0 ohm testing the same way you did (got the ECM in mine so should be close to what you got on your GN).

I suspect the starter as you mention and I also got a brand new alternator with the Racetronix fuel pump "boost" harness so I will check that as well to make sure it's ok and no shorts to ground anywhere But I do suspect the starter wires as they did twist and I can see from a picture I took the main positive might touch on the heat shield possibly .... will get under there tomorrow.

Again, thanks for the prompt response.

 

[Jan Larsson]

Sorted, cables at starter where touching something. Took them off, repositioned then tightened the nut making sure they would not twist and it work fine.

Not started the engine yet but electrical works fine, fuel pump works and keeps pressure and no leaks so good start

Thanks for the help.

 

[83ttypecooled]

Hi Jan,
I am happy that your short was so easy to find. I was fearing the worst; pinched harness or such. Anyway,you should have one of the premier TTAs out there soon,and I must say I am totally impressed with your dedication to this project.
It won't be long now before you crank it up,so break out the celebratory beverages when it happens! As always, good luck, my friend!
Dale

 

[fast400]

...updates

 

[Jan Larsson]

...updates

Running .... YouTube - TTA 1078 Alive Again
:biggrin:

 

[garyk1970]

excellent