Videobob describes Delorean electrical system

[jammer96]

This is a 40 minute video, but it seems to be pretty accurate description.

http://www.ustream.tv/recorded/3923885

[Hmm252000]

Good for the most part. A few minor facts he got wrong:

Main headlight power doesn't go through the headlight switch.
Highest power alternator isn't always the best route to go due to idle conditions.
You can't run gel cell batteries flat without damaging them.
Both fans run at the same time, regardless if it's engine temp or AC.

The video cut out at about 20 minutes, so I don't know what the second half says. Still overall good info for a new owner.

[Justice]

"This thing is in fucking spanish... what country am I in?"

Classic.

I don't have a delorean, but this is what I like to know and see when I do have one!

[content22207]

What melts the headlight switch is heat from the internal illumination bulb, not amperage from the headlight circuit. In the headlight setting, only relay trigger voltage passes through it (about 1/3 amp IIRC).

It is true that side and tail light voltage passes through the switch, however. Is that enough to melt the switch? Debatable.

The real design fault is that *BOTH* fuses (there are two, one each for low & high beams) are downhill from the switch, yet there's a ground from the switch itself, creating the possibility of an unprotected short. If the switch melts and any of the power feeds contact that ground (remember: the internal illumination line is hot whenever the car is energized, day or night), the ground wire will get hotter & hotter until something catches fire:

I also melted the wiring harness under the console in several places.

Bill Robertson
#5939

[Hmm252000]

Originally Posted by content22207

It is true that side and tail light voltage passes through the switch, however. Is that enough to melt the switch? Debatable.

I would say yes, the current is enough to melt the switch. If it was just the bulb, why haven't any hazard switches melted yet? We'll know for sure if it's the internal bulb if we ever hear of a switch melting after having the relay bypass installed.

I do agree that there should have been a fuse installed earlier in the line. Having such a long length of unfused wire isn't safe.

[content22207]

Hazard switch is a simpler switch. (I now use a hazard switch to drive my headlights BTW). Front and rear turn signals pass through the hazard switch (side lights too if you've made that mod).

Problem isn't the length of wire -- it's the unprotected short circuit. Doesn't matter how long a wire is -- a dead short is still a dead short. You can set your car on fire just fine with a piece of wire long enough to reach both battery terminals (or the side of a metal body car).

Ever accidentally contact the other terminal with a wrench while tightening the terminals? (Usually a top post experience -- you only make that mistake once).

Bill Robertson
#5939

[Hmm252000]

Hazard may indeed be a simpler switch, but it's got the same bulb in it which also runs for the same amount of time. If it was the bulb causing the meltdowns as you suggest, then we should in theory have an equal number of hazard and headlight switch failures from meltdowns. Since it's just the headlight switches, that would indicate a current issue and not a bulb issue.

As for the unfused wire, yes any circuit that has a large unprotected segment is bad. I was simply saying the longer the length of wire, the more risk there is.

Fortunately I've learned from other people's mistakes to have never dead shorted a car battery at the terminals.

[videobob]

I will have to do some more investigation on some of these things to see
what I have right or wrong, I am always willing to admit my wrongs.
I do know that a lot of switches have melted over the years so my
theory of cutting out extra voltage using LED's should be valid.

Also, as far as I know Gel batteries are supposed to be much more
resilient to being run down and charged quickly.
They come with a great warranty regardless!

As for those fans, people have been building boxes like Fan-Zilla
for years to make the fans alternate on and off, back and fourth
so they don't both come on at the same time.
If both of your fans are running all the time then most likely someone
has bypassed your otterstat as well as your relays to make this happen.
As I understand it, the factory design uses a temp sensitive otterstat
that turns the 1st fan on at a certain temp, then the other one additional
when the A/C is on.
I could be wrong about that....I usually rig my fans to run balls out all the time!!!!

Originally Posted by Hmm252000

Good for the most part. A few minor facts he got wrong:

Main headlight power doesn't go through the headlight switch.
Highest power alternator isn't always the best route to go due to idle conditions.
You can't run gel cell batteries flat without damaging them.
Both fans run at the same time, regardless if it's engine temp or AC.

The video cut out at about 20 minutes, so I don't know what the second half says. Still overall good info for a new owner.

[Ashyukun]

Originally Posted by videobob

If both of your fans are running all the time then most likely someone
has bypassed your otterstat as well as your relays to make this happen.
As I understand it, the factory design uses a temp sensitive otterstat
that turns the 1st fan on at a certain temp, then the other one additional
when the A/C is on.
I could be wrong about that....I usually rig my fans to run balls out all the time!!!!

You're right about the fans running all the time=jumpered otterstat, I know that because it's the situation I'm in (it's easy & cheap enough to get a new one, but I don't want to have to deal with draining the coolant to replace it). Since I'm running new pancake fans with a lot lower draw, I don't worry too much about it (though I do badly need to track down a kickdown solenoid for my carb to bump up the idle when the AC is running...).

I'm pretty sure though that in stock configuration the fans both kick on at the same time with no sequencing. The original design (with or without the fan fail module) only had one relay for both fans, so there isn't really any way that it could have not kicked them on at the same time. There are mods (like Toby's that I'm running) that rewire the system to give each fan its own relay so if something happens to one relay at least the other fan will still run, but I'm 95% certain that unless you're running something aftermarket that both fans cycle on or off simultaneously...

[Hmm252000]

Originally Posted by videobob

As for those fans, people have been building boxes like Fan-Zilla
for years to make the fans alternate on and off, back and fourth
so they don't both come on at the same time.
If both of your fans are running all the time then most likely someone
has bypassed your otterstat as well as your relays to make this happen.
As I understand it, the factory design uses a temp sensitive otterstat
that turns the 1st fan on at a certain temp, then the other one additional
when the A/C is on.
I could be wrong about that....I usually rig my fans to run balls out all the time!!!!

Fanzilla and other similar boxes simply delay the start/stop of the second fan. After a few seconds both fans are running. The otterstat is a simple on/off device. When triggered, both fans are supposed to run. Same with AC. If somebody has a fan system where only 1 runs in most conditions, they've either done a massive amount of customizing (there are aftermarket controllers that can do what you describe but wouldn't be plug and play) or they have a bad fan.