I already have some good info from other posts here... but want to see if I am overlooking anything.

I have a 125 foot run of underground conduit (1") with 3- #6 strands. This is the power supply for my garage and well.

Somehow I lost one conductor. I have a temp in place and am preparing to pull new conductors through the conduit.

Questions.
Should I pull out the old wires and use them to pull a rope through which I will subsequently use to to pull the new wire with?

Should I use the existing wires (or just one of them) to pull the new ones through?

Should I replace all the conductors or just the one thats failed (which I have identified)?

I am concerned about the 1" conduit and any 90 degree bends to pull through. I can easily use a power winch I have to do the pull... and am inclined to go ahead with that But... I wonder in manual has any advantaged such as... knowing when the wires are hung up... during the pull!?

Thanks

Any other advice? I understand tapering the end, using lubricant,

Let's look at the options you proposed:

1. Pull out the old and use a pull rope.
What's wrong with this?
Well, doesn't it make sense to pull something the same diameter as the pulling system if you can? There is less reason to hang up. So use the entire bundle to pull new wires + a pull string

2. Existing or one of them: Same reason, but more importantly, you cannot get one out of the bundle without getting a tangled mess.

3. You could replace just one: IF the previous person doing the work left a pull string. I think you left pulling all of them.

4. Use plenty of lubercant. Taper the new set of wires and tape SECURELY together. Have a helper. And pull a pull string at the same time. Make sense?

An Amp meter will show the amount of force in amps, and is relative. Remove wires and pull in a rope or fish tape. If only 2 90 degrees, Pushing a fish tape is easy enough, Strip wire back, remove some strands to have some taper, tape well and lubricate. A person that can feed wire effectively can make job easy. If doing by yourself, support wire so weight of wire will help you to pull, Could be roof, extension ladder where wires are fed from. Lubricant.