Did you know that the network fee still applies with the sweeping function? It's essentially the same thing and please, look at my post. That is probably the reason why you cannot sweep.
No, I didn't know the fee applies to sweeping function too.
If you don't want to spend the Bitcoins on fees, create a new wallet, select standard wallet and select use public or private keys. After keying your private keys in, you should be able to use your coins on Electrum (Only if they are confirmed and unspent).
I personally don't recommend this but if you don't want to pay the fees, here you go.
If his addresses have many inputs as he say,he will have problems when import private keys in Electrum.Recently I do the same and with address which have many inputs wallet just not responding/freezes.He can try to import one by one,and if some work then try to transfer to new Electrum address,for others addresses only way is to use blockchain wallet and send BTC to new address.
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Electrum freezes when I try to send bitcoins
This might happen if you are trying to spend a large number of transactions outputs (for example, if you have collected hundreds of donations from a Bitcoin faucet). When you send Bitcoins, Electrum looks for unspent coins that are in your wallet, in order to create a new transaction. Unspent coins can have different values, much like physical coins and bills.
If this happens, you should consolidate your transaction inputs, by sending smaller amounts of bitcoins to one of your wallet addresses; this would be the equivalent of exchanging a stack of nickels for a dollar bill.
This might happen if you are trying to spend a large number of transactions outputs (for example, if you have collected hundreds of donations from a Bitcoin faucet). When you send Bitcoins, Electrum looks for unspent coins that are in your wallet, in order to create a new transaction. Unspent coins can have different values, much like physical coins and bills.
If this happens, you should consolidate your transaction inputs, by sending smaller amounts of bitcoins to one of your wallet addresses; this would be the equivalent of exchanging a stack of nickels for a dollar bill.
https://electrum.readthedocs.io/en/latest/faq.html#electrum-freezes-when-i-try-to-send-bitcoins
