Rewiring, Should I go ISIS multiplex or "old school analogue?" Options

[phillstek]

As the respray on my car approaches completion it is time to consider what to do about the wiring. Here is a bit of background info that may be relevant.

The car was converted to rhd back in 1988. Part of the conversion involved extending the harness from the fuse box to the instruments, switches and ignition and pulling it over from the left to the right side of the dash. It was always dodgy and I've had a couple close calls with electrical fires as well. The rest of the wiring is original to a certain degree although a lot of the connectors are green/corroded looking. The fuel tank sender plug is cracked and a few wires hang loose here and there. There are relays that don't appear to do anything at all etc etc.

Essentially, I don't want to risk any further incidents and have decided to get the car completely rewired from scratch.

I've had some quotes for a traditional job but for not much more, I can have it done with the ISIS.

I'm leaning heavily towards the ISIS.

Does anyone want to tell me why I shouldn't use it and why I should stay with the old school wiring.

Thanks,

Phil

[AndyB]

IMHO I say go for the modern harness. I have also looked into the ISIS and I like it for its simplicity. The only downside is price.

[phillstek]

IMHO I say go for the modern harness. I have also looked into the ISIS and I like it for its simplicity. The only downside is price.

Thanks for your input and confirming my preference.

Yes, the simplicity appeals to me also. The price either way is going hurt, so ultimately whatever system is the most reliable/safe is more my priority.

Anyone else have something to add?

Phil

[edwin]

hi there.
I found out today how fun it is fitting a new speedo to a RHD 914. that cable is only just long enough.
I have 2 cars here that i would be interested in new wiring harnesses if you were getting one made might bring costs down?
What are the benifits of doing this and what will need to be changed?
I am converting to EFI in Jan so wont need any of the engine related items.
Keep us posted
Edwin

[Hontec]

Phil,

I decided a while ago to go for ISIS in my 914, it's such a beautiful simple system.....

[edwin]

Just had a look at the website.
I need one of those in my life!
http://www.isispower.com/
video on the main page gives a good idea of the potential.

[realred914]

looked at teh website, whow pretty expensive, adn complex looking, nice dainty wires to.

I'd go with a stockish wire stockish wire system. you can uy sppols of colored wire (use the fine strand "primary wire") get some quality indusrtial connectors (radio shack has some good ones) lots of sleaving and heat shrink, and some tape and tie wraps.

the 914 electrical is really simple, easy to remake, I remade one for a kit car, using the 914 fuse block as a start..

i'd avaoid the isis sytem, looks funky, over priced, not needed.
you should be able to do your own really nice job on this without isis.

then you have to ask, what is isis?

[JeffBowlsby]

All I see is some parts on the ISIS website. What would an entire chassis harness cost and what would be included? Why would it be superior to stock?

Whatever solution, it either needs to be compatible with the 914s components - guages, switches, lights, engine bay connections, charging system etc. - or those items also need to be changed. Seems like another slippery slope project - little gain for Lots O' Cash.

[euro911]

I was going to recommend your harnesses Jeff ... you beat me to it.


(IMG:style_emoticons/default/idea.gif) That reminds me ... I think I need to upgrade some harnesses on my wife's 71 soon

[SirAndy]

Does anyone want to tell me why I shouldn't use it and why I should stay with the old school wiring.

A few years ago i bought a (used) completely unmolested, perfect main wiring harness from a wrecked '74 and used it to replace the hacked up harness on my '70.

The differences between the years made this a little bit more complicated as i had to change some accessories to match the '74 harness, but my main point is, i paid $100 for the complete harness. With every single connector and plastic plug on it. All in pristine condition.

It seems, if you can find a good original harness for your year, you'd be way ahead in terms of money spend.
You can then extend the wires needed yourself, so you know it was done right.

If you are somewhat handy with car wiring, you can extend everything without even cutting a single wire .

Just my 2 euros ... (IMG:style_emoticons/default/bye1.gif)

[phillstek]

Thanks everyone. Finding a good used one here is impossible so that is not an option. I also don't have the time/patience to make the harness myself and getting all that colour coded wire would be a complete pain.

The cost of having someone else do either to completion, is approximately the same(about 10% more for ISIS).

One of the benefits of multiplexing is substantial weight saving.

Jeff, just owning this car is one huge slippery slope and when I consider the total amount spent over the years it makes me shudder, but I love it and just want to get the car to the point where everthing is done correctly and I can enjoy it again.

Realred, I'm not sure what ISIS means but I'll try and find out when I go see them next week.

Anyone else want to add their thoughts.

Thanks again to all,

Phil

[JeffBowlsby]

I have over a dozen stock chassis harnesses, from each year of production (they are all different). Some are in excellent condition, others need repair. What year is your car?...maybe I have one available that would work for you.

These cars don't have to be slippery slopes, but they can sure blow a budget in a hurry if you let them get out of hand.

(IMG:style_emoticons/default/wink.gif)

[Mike Bellis]

The ISIS system looks really cool. It also looks overly complicated for the primitive 914. If you have a full show car, Modern Electronic Fuel Injection, ABS and every other high tech gadget in you 914... The price for the components on the website is too cost prohibitive. If in Australia the cost is only 10% more... You guys are getting ripped off by your mechanics.

I would recommend you talk to Jeff about a harness and save your money and the programming headache.

[Jake Raby]

I am using the ISIS system in my double cab.. If the system performs well I have already been granted a distributorship..

The ISIS system has lot of benefits, especially if you want to do away with relays and other crap like I do.

[phillstek]

Thanks again to all for your valued comments.

Ok Jeff here is some more info. The car is a '72 that has been converted to a six. I am currently using Webers but I am also considering an EFI conversion or perhaps even a Subi conversion down the track. Bear in mind that whatever harnesses you may have, they all came out of a left hand drive car and would need to be patched to suit my rhd conversion. So I'm back to where I started.

Not to cast aspersions on the quality of your parts, but I don't see a lot of point in pulling a 40y.o. harness to replace it with another 40y.o. harness either.

I agree, the 914 system is primitive and the ISIS system looks really cool. While I won't be running ABS, ESP, SRS Airbags etc, I want to use LED strips to light all interior, trunk and engine compartments and I also want to ditch all of the relays and heavy copper wire.

Regarding the costs of the components/labour and whether they represent good value or not, again either system is around the same amount so that's not influencing my thoughts at all.

Keep in mind the quotes I've received are for a complete rewire (with all the connectors, programmed and everything hooked up and working).

I'm still leaning towards the ISIS but remain open to anything that can convince me otherwise.

Thanks,

Phil

[SirAndy]

but remain open to anything that can convince me otherwise.

I think you already made up your mind and you're just looking for someone to back you up on your decision. (IMG:style_emoticons/default/smile.gif)

There is nothing fundamentally wrong with a unmolested 40 year old wiring harness in good condition.

And using the fact that you would have to extend wires on your dash is moot because the alternative is a completely custom harness, where every single wire is *custom* ...

As for availability, as Jeff has already mentioned, good replacement harnesses are pretty plentiful here in the US, and even with shipping, you're probably looking at less than $300 - $400 for a complete and unmolested harness.

Again, i don't think you are really looking for options as much as you're looking for confirmation that ISIS harness will be a good choice for you.

(IMG:style_emoticons/default/bye1.gif)

[phillstek]

I really haven't made a decision either way as yet. I'm going out to see some guys that can do both on Monday. They didn't push either system above the other and suggested I discuss it with them at length to determine which would best suit my needs. That sounded like a smart way to go to me.

I respect the opinions of all those with far more experience than me but I am struggling to accept that a used harness is better than a brand new harness.

Phil

[edwin]

You will be much better off if you go with an original harness and have it modified.
there isnt really much to do and if you had the dash appart then it would be much cheaper to do it that way than redo the whole lot from scratch.
I really do like the idea of those ISIS style sytems but the price is overkill compared to using a standard.
I would spend the money on an efi conversion over that system anyday.
I think by looking at guys who are doing these sort of installs they will naturaly push to sell the stuff that makes life "easier" for them.
Either way you will end up with much the same result.
Hope this doesnt sound like i'm flaming you but it can be done much cheaper if thats an issue.
Edwin

[ejm]

From the ISIS installation safety warnings:

Also, if the alternator is fluctuating, ISIS™ Intelligent Multiplex System™ will turn off. This will turn off the car.

Sounds reliable (IMG:style_emoticons/default/icon8.gif)

The car was converted to rhd back in 1988. Part of the conversion involved extending the harness from the fuse box to the instruments, switches and ignition and pulling it over from the left to the right side of the dash. It was always dodgy ...

Find a good used harness and stay with stock. Rather than extending the wiring for the dash I would flip everything and move the fuse box to the right side also. This should let all the wiring reach unaltered. The harness for the front trunk can go out the right side, you would need to swap the wires for L-R front signals and relabel some fuses for L-R.

[phillstek]

From the ISIS installation safety warnings:

Also, if the alternator is fluctuating, ISIS™ Intelligent Multiplex System™ will turn off. This will turn off the car.

Sounds reliable (IMG:style_emoticons/default/icon8.gif)

The car was converted to rhd back in 1988. Part of the conversion involved extending the harness from the fuse box to the instruments, switches and ignition and pulling it over from the left to the right side of the dash. It was always dodgy ...

Find a good used harness and stay with stock. Rather than extending the wiring for the dash I would flip everything and move the fuse box to the right side also. This should let all the wiring reach unaltered. The harness for the front trunk can go out the right side, you would need to swap the wires for L-R front signals and relabel some fuses for L-R.

Thanks ejm. I have had issues with the alternator (exciter diodes frying) in the past so that is defintely a concern.

I'll investigate the possibility of flipping the fuse box etc, to the other side. I don't know why I hadn't considered it before, so thanks again for that suggestion.

Phil