Thoughts on ISIS Intelligent multiplex system

[newtonhubcap]

In the process of planning direction of restoring 2 1971 240Z, I am looking at the wiring system of the cars. Although the wire harnesses appear to be in good shape, it seems that that originally there was a capicity issues (ie headlight relay upgrades etc.).

The ISIS system is comparmentized, you have a main power block, which would then control the power to two additional power blocks such as one in the engine compartment and the one to handle the rear harness section.

Personally, I think this would upgrade the car(s) significantly and make the electrical system more reliable?

Appreciate everyone's thought of going this route!

newtonhubcap

[SteveJ]

Capacity issues? Not really, unless you add a bunch of new electronics: stereo, etc.

Relay upgrades take care of the fact that the current for the headlights & parking lights goes through the switch contacts.

Alternator upgrades typically resolve issues for people with low output at idle or handling a larger stereo, etc.

IMHO, it seems that there is a potential for a significant cost for the ISIS system as compared to solutions that have already been engineered.

[5thhorsemann]

There are definite capacity issues in the Z wiring, under sized conductors, over current and conductivity problems at the fuse block that cause the fuses and the block itself to melt etc. I am not familiar with ISIS, but it has to be better than what’s there now. I have already changed all the wiring associated with the lights, upgraded the alternator, and rebuilt all the switches on the column. Let’s face it, aside from the rust problem, the wiring is the No. 2 issue these cars suffer from.

[Zed Head]

It's the switches and connections that are the problem, after 30-40 years of time.

What is "the ISIS" system?

[sblake01]

I have seen that sytem used on an S30 but I've seen it on a coulple of 'hotrods' Here's their website which contains a video on the system:

http://www.isispower.com/

[Zed Head]

Thanks for the link. It might also be convenient for connecting an aftermarket engine management system at the ECU connector, with easy added functionality, if it does what I think it does. I couldn't find a simple explanation of functions on the web site though.

It looks like a programmable multi-input, multi-output relay.

[SteveJ]

I was thinking programmable relay, too. I can see it as a way to replace a wiring harness that has been hacked to death by a previous owner.

[Oiluj]

Nice system, but seems a bit overkill to me. Add a few of Dave's light relays, better wiper relay, relay for electric fan, one for a high-power sound system, (if you go that way), and your'e done. It's all plug n' play.

Just my 2 cents...

[Rainman]

The Isis system looks like a very easy way to modernize the Z electrical system.. I suppose it depends on the ultimate goal of the restoration is..

There are cheaper ways to make the system better than original by adding the relay kits that Julio mentioned, but if you intend to convert to LED lighting, and want to add some neat-o automatic features that the modern cars have like dimming interior lights, headlights that turn off 30 secs after the ignition is powered off, etc.. then this is a great way to do it. I really like the theft features this system incorporates.. Great piece of mind as they are very easy to break into hotwire..

[5thhorsemann]

It's the switches and connections that are the problem, after 30-40 years of time.

The switches are under sized for the associated loads IMO, by using the relays you are basically just using the switches for a signal current in the milivolt range which keeps the guts from getting hot. Age is not as big an issue as the lack of capacity in these devices. Even using the isis, you would still be using the original switch gear in many cases to keep the cabin aesthetics original.