Present Perfect

Yes, I think you should put the first verb in past perfect, since the fact no longer holds true (if I understand your mechanics aright).

1. I have never had a problem with my heater draining the battery except for that summer summer I replaced a fried rectifier. (Is this okay with present perfect? Could I also use past perfect here too?)

Thanks.

Interesting. I wonder whether we can say that the "Then again" corrects the present perfect + "never" of the first sentence, as a stylistic device.

Though it is a little unclear and tortuously written. Maybe:

1. I have never had a problem with my heater draining the battery. Then again, last summer I had to replace a fried rectifier.

Nice observation, MrP. In discourse, it could well be. I would like to see the speaker expostulate more about his poor memory, however.

Are both of these correct? If not, why?

1. I have been calling them for 30 minutes now and no one is picking up.

2. I have been calling them for 30 minutes now and no one was picking up. (If this one is incorrect, why so? #1 is right and #1 uses only past tense? Is the structure for #2 supposed to be present perfect + present tense?)

3. I have been calling

<Are both of these correct? If not, why?>

You say "both", but you posted three examples.

<1. I have been calling them for 30 minutes now and no one is picking up.>

Correct.

<2. I have been calling them for 30 minutes now and no one was picking up. (If this one is incorrect, why so? #1 is right and #1 uses only past tense? Is the stru

Well, I definitely like and use #3. I suppose that #1 is possible in conversation, with the speaker stressing that there has still been no answer right up to now (yet note that I automatically go to present perfect in my explication). #2 repels me.

That's interesting. Maybe there's a BrE/AmE division here. I'd say:

1. I've been calling them for 30 minutes now and no one is answering. ] Fine; neutral.

2. I had been calling them for 30 minutes and no one was answering. ] Fine as modified.

3. I've been calling them for 30 minutes now and no one has been answering. ] Fine; "emphatic" or "poi

1. Sorry, it has taken me a while to get back to you. I was busy. (Is this one correct? It is better to use #2 right?)

2. Sorry, it has taken me a while to get back to you. I have been busy.

3. Sorry, it took me a while to get back to you. I was busy. (Are #2 and #3 pretty much the same in meaning except that #2 states a time in the past

Hello Jack

I've changed them slightly, to make them more idiomatic:

1. Sorry it's taken me so long to get back to you. I was busy. ] I am getting back to you now. I was busy.

2. Sorry it's taken me so long to get back to you. I have been busy. ] I am getting back to you now. I was busy and I'm still busy.

3. Sorry it took me so long to get back to you. I was bu