After the thunder sent Doc Brown back to 1885, and after Marty received the letter, why didn't the 1955 Doc send him back to the future (either 1985 or 2015) to completely repair the Time Machine and then travel to 1885?

In 1985 the Doc could have used spare parts or something to repair the time/flying circuits or in 2015 perhaps even any service shop could repair the flying circuit and the Doc could easily fix the time circuits.

I recall Doc saying the bolt destroyed the flying circuits (in the letter), so it would perhaps be convenient to enable them again, taking into account there are no roads, it would easily reach 88MPH and gasoline would not be so important.

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    The time machine was fully repaired, and there were plenty of long paved roads in the 1800s, more than sufficient for a car as powerful as the Delorean to reach 88mph
    – Valorum
    Commented Dec 6, 2022 at 21:48
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    @Valorum Respectfully I don't recall any paved roads in 1885 Hill Valley. youtu.be/yYdFMt9HJv4. A vehicle could probably get that speed on the wagon trails of the desert. In a rural town in 1800s USA the progression would be dirt to wood planks to bricks as the city developed and Hill Valley was still at the dirt stage. Commented Dec 6, 2022 at 22:52
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    @lucasbachmann - That main road would be more than sufficient, even with the Delorean's crappy 130BHP engine and fat ass
    – Valorum
    Commented Dec 6, 2022 at 22:57
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    An actual road wasn't strictly necessary, just level ground. Marty didn't use a road to go back to 1885. Commented Dec 6, 2022 at 23:35
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    @Valorum Are you thinking 4th dimensionally?
    – user15742
    Commented Dec 7, 2022 at 22:24

2 Answers 2


The film suggests that the 1955 Doc repaired the time circuits before Marty went back to 1885. The letter from 1985 Doc specified that the parts needed to repair the time circuits would be available by 1947, and Marty indicated that 1955 Doc was fully capable of repairing the time circuits on the DeLorean.

1985 DOC: I set myself up as a blacksmith as a front while I attempted to repair the damage to the time circuits. Unfortunately, this proved impossible, because suitable replacement parts will not be invented until 1947.

MARTY: It's not gonna happen, Doc. After you fix the time circuits and put new tires on the DeLorean, I'm going back to 1885, and I'm bringing you home.

Also, the fact that Marty was able to go back to 1885 is evidence in itself that the time circuits on the DeLorean were repaired. There's nothing in the film that suggests they weren't fully repaired.

As for the flying circuits, 1955 Doc presumably wasn't able to repair those, as, according to Doc's letter, those weren't just shorted out, like the time circuits, but outright destroyed.

1985 DOC: The lightning bolt that hit the DeLorean caused a gigawatt overload which scrambled the time circuits, activated the Flux Capacitor, and sent me back to 1885. The overload shorted out the time circuits and destroyed the flying circuits. Unfortunately, the car will never fly again.

This suggests that the flying circuits were irreparable, and needed to be fully replaced, which likely would've required technology from 2015, or at the very least, the knowledge 1985 Doc gained whilst in that time period.

You've proposed that 1955 Doc could've sent Marty to either 1985 or 2015 in order to fix the flying circuits, but let's think about that for a moment. Who would've fixed them in 1985? The hovercar tech didn't natively exist in that time period, and neither did the 1985 version of Doc, since he'd been sent back to 1885 and died there in the then-current timeline.

Theoretically, Marty could've time travelled to a point in 1985 shortly before the events of the first film and interacted with Doc then, but interacting with Doc at that point would've risked a major disruption to the timeline, and thus a time paradox. It was hardly worth taking that risk in order to fix the flying circuits on the DeLorean, which weren't necessary for what Marty needed to do in 1885.

Also, that version of Doc hadn't been to 2015 yet, and likely didn't have the knowledge required to fix the flying circuits, since he didn't invent that technology himself.

As you proposed, Marty also could've travelled to 2015 with the intention of having the flying circuits fixed, but who would've fixed them there? Again, the older version of Doc who was familiar with that technology had been sent to 1885 and died there in the then-current timeline. You mentioned a "service shop," implying that a random mechanic from 2015 could've done the job, but allowing some random mechanic to work on the DeLorean would've risked that person discovering the time travel technology in the vehicle, which Doc kept closely-guarded for obvious reasons.

We don't strictly know whether 1985 Doc allowed others to work on the DeLorean in order to upgrade it with hovercar tech, or whether he performed those upgrades himself (using knowledge he acquired in 2015). Ideally, I think he would've preferred to have performed those upgrades himself, to minimise the risk of others discovering his time travel tech. But if he did allow others to work on the car, I imagine he likely would've removed at least some of the more conspicuous components of the time travel tech first, to help keep that stuff under wraps.

As far as we know, Marty wouldn't have had the knowledge required to uninstall and then reinstall things like the Flux Capacitor himself, so if he'd have taken the DeLorean into a service shop in 2015, he'd have had to've left that stuff on full display. It doesn't make sense to think that either he or 1955 Doc would've been willing to take that risk, especially in order to fix the flying circuits which, again, weren't necessary for what Marty needed to do in 1885.

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    We learn that he "had the car" hover-converted, strongly implying that he took it to a garage rather than doing the work himself. Other than that, a fine answer
    – Valorum
    Commented Dec 6, 2022 at 23:26
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    One can also note that if the DeLorean needed a whole new hover conversion in 2015 it would have cost $39,999.95, and we don't know where that cash would come from.
    – N. Virgo
    Commented Dec 7, 2022 at 7:45
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    Also 1947 is probably a reference to the invention of the transisor - but 1955 Doc probably fixes it using vacuum tubes, since the new time circuits take up a huge box strapped to the front of the car.
    – N. Virgo
    Commented Dec 7, 2022 at 7:50
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    I thought you mixed up the centuries but now I'm not sure. Thinking in 4 dimensions is confusing either way. Rollback if I made it worse. Commented Dec 7, 2022 at 17:23
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    @Hannover Fist - I reversed the changes with a subsequent edit. The idea behind referring to the older version of Doc as '1985 Doc' is to specify the time period he was natively from, rather than the one he was currently in. This allows me to refer to him the same way, regardless of which time period he's in when I'm talking about him. It also allows me to distinguish between the older and younger versions of Doc even when they're in the same time period, like they were in the second film. I guess referring to them as 'Old Doc' and 'Young Doc' would be another way to go. Commented Dec 8, 2022 at 9:57

1885 Doc takes great pains to highlight the danger of time travel in his letter to Marty and 1955 Doc:

Do not — I repeat — do not attempt to come back here to get me. I am perfectly happy living in the fresh air and wide-open spaces, and I fear that unnecessary time travel only risks further disruption of the space-time continuum. And please take care of Einstein for me. I know that you will give him a good home. Remember to walk him twice a day, and that he only likes canned dog food. These are my wishes; please respect them and follow them.

Even if Marty and 1955 Doc think it's worth the risk to make an extra trip to 1885 for the rescue mission, they wouldn't necessarily think it was worth three extra trips to go to 2015 (which neither Marty or 1955 Doc know much at all about), then go to 1955 to drop off 1955 Doc, then go to 1885, especially after the whole mess of Part II started from what was supposed to be a simple errand to get Marty's son out of trouble.

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