Where to tie in HEI? - Page 2 - Chevelle Tech
Electrical & Wiring Troubleshooting electrical problems.

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post #16 of 35 (permalink) Old May 16th, 18, 6:00 AM
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Re: Where to tie in HEI?

Of course relays are reliable. Nonsense to suggest otherwise. Like any man made device, they can fail, but it is rare, not common. I spent 5 years working in a telephone exchange in an era when relays, thousands of them, controlled telephony. Failure was extremely rare [ do not recall a failure, ever ], but contacts reqd cleaning & adjusting. The cleaning was reqd due to oxidation, not wear, because of the extremely small currents [ milliamps ] being switched, so there was little 'wetting' [ look it up ] action of the contacts. This is not a problem with our vintage cars where relays contacts pass much higher currents.

Here is the best example of relay reliability that all on this forum can relate to: the humble voltage regulator.
For decades until solid state regulators were introduced in the 1970s, VRs used a relay [ sometimes two ]. They energised/de-energised so fast that they were often known as a vibrating contact regulator. They had a tough life. They were extremely reliable & there are probably some reading this that have the original 40+ yr old reg still on their car...
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post #17 of 35 (permalink) Old May 16th, 18, 8:35 AM
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Re: Where to tie in HEI?

Look at any modern day car and you will find probably 10+ relays powering everything from engine computers to power seats. I specialize in auto electrical diagnosis and can tell you that relay failure rate is minimal. More problems are caused by bad grounds than any other single issue. A relay is not a bandaid, but a better way to prevent voltage drop in a circuit. I have measured relay voltage supply in vehicles with 100k+ miles and found them to be within 5% of battery voltage. While a relay is not needed in this particular case, it is a great alternative to upgrade 50 year old wiring.
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post #18 of 35 (permalink) Old May 16th, 18, 8:43 AM
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Re: Where to tie in HEI?

BUT, how many of those relays were thrown in somewhere that wasn't designed for a relay and wired up by a DIYer? NONE

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post #19 of 35 (permalink) Old May 16th, 18, 9:13 AM
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Re: Where to tie in HEI?

Panasonic makes Bosch automotive style relays, up to 40 amps. I trust the Panasonic brand way more than any other relay regardless of brand name. Except for one Hella delay off relay, all the relays on my car are these 40 amp Panasonic relays. Their case is actually smaller than others.

While I totally agree with Dave Ray's assessment of every added part is a potential failure point, I believe relays today are reliable enough to be used to feed equipment that needs a clean and direct source of power.

That said, Dave Ray is correct, an HEI ignition should be able to operate with a feed from the "IGN" terminal on the fuse block without a relay.

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post #20 of 35 (permalink) Old May 16th, 18, 9:40 AM
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Re: Where to tie in HEI?

Quote:
Originally Posted by paul bell View Post
Panasonic makes Bosch automotive style relays, up to 40 amps. I trust the Panasonic brand way more than any other relay regardless of brand name. Except for one Hella delay off relay, all the relays on my car are these 40 amp Panasonic relays. Their case is actually smaller than others.

While I totally agree with Dave Ray's assessment of every added part is a potential failure point, I believe relays today are reliable enough to be used to feed equipment that needs a clean and direct source of power.

That said, Dave Ray is correct, an HEI ignition should be able to operate with a feed from the "IGN" terminal on the fuse block without a relay.
I'll add in another thing about relays, if wired correctly, they do provide good current isolation, and work very well. And if done neatly in quality sockets, can last. But if you are concerned about how long they last, or worry about them failing, think of them as fuses, keep 2-3 spares at all times, and test your spares before you need them. Another concern is, relays for fuel pumps and ignition make your car VERY ease to steal/hotwire. Pull the relay, stick in a bent anything metal, and you have ignition/fuel.
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post #21 of 35 (permalink) Old May 16th, 18, 10:28 AM
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Re: Where to tie in HEI?

Relays, as a device , are and have been used in industrial applications for many decades.
In pipeline control systems, we interposed relays in probably 90% of the circuits needed to operate a pump station.
These relays have been known to work for many years without failure.
I know of relays panels that I built that are over 40 years old, still in service without any failures. The cost of those devices is naturally higher than the relays that can be picked up at Joe's Auto Parts.
In the automotive world, relays are used extensively to keep the power loads regulated.
There are some systems where relays are a definite advantage.
Headlights and electric fuel pumps come to mind.
I think personal preference is a big factor in the decision to use or not use them.
If you don't like relays, don't use them. If you do, then go ahead.
It's not up to anyone else to make that decision.
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post #22 of 35 (permalink) Old May 16th, 18, 10:46 AM
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Re: Where to tie in HEI?

If a relay fails, a jumper/s can get the car home.

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post #23 of 35 (permalink) Old May 16th, 18, 11:14 AM
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Re: Where to tie in HEI?

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Originally Posted by oldcutlass View Post
If a relay fails, a jumper/s can get the car home.
Good point and a jumper from battery + to BAT + terminal at the coil works also.

Of course relays installed be professionals are pretty doggone reliable but to infer that they don't fail is not true.

Thousands and thousands of relays are being sold to replace defective ones every day and I have replaced hundreds over the last 40 some years myself.
I stocked many different replacement relays in each of my six service trucks and sold many when I was in business.
(Replaced a circuit board with a bad relay on a furnace a couple of weeks ago.)

The thing is why add a relay when it's not needed?
different strokes for different folks.
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post #24 of 35 (permalink) Old May 16th, 18, 2:40 PM
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Re: Where to tie in HEI?

So, it seems that EVERY vehicle in the world that ever existed, and still do, need to be brought back in and have a billion dubious relays installed, by "professionals" to everything from ignition systems ti wireless headphones.

PLEASE, I do ignition systems for a living, see more than a LOT of basically well meant wrong stuff done, like relaying up a car for NO reason, and fix it when it fails, which is way past too often.

Of course, all you folks are all professionals, in automotive electrical systems and especially ignition systems, just why haven't you all convinced all the manufacturers to add every relay they possibly can to an ignition system, and fuses, and diodes, all sorts of electronics that really haven't needed to be there, FOR THE LAST 100 PLUS YEARS?
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post #25 of 35 (permalink) Old May 16th, 18, 5:46 PM
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Re: Where to tie in HEI?

I changed mine to a relay powered HEI in 1996 and have had no relay failure in 22 years of being a well used daily driver. It was quicker to rig up a relay than to pull out the resistance wire and replace it. Modern cars (especially German ones) are chock full of relays that do not seem to be a problem. If you want to use a relay , do it.
As far as identifying symptoms and problems, I think that powering the HEI off the original light gauge wire of the original system is likely to deliver lower voltage than using a relay. Just replacing the resistor wire with an upgrade fails to upgrade the rest of the power wiring. That is the problem.
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post #26 of 35 (permalink) Old May 16th, 18, 7:38 PM
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Re: Where to tie in HEI?

Yes, to each his own.

Whether you take advantage of existing circuits, or create new ones, the responsibility falls on the modifier of said vehicle to make sure the system is safe, reliable and providing the needed condition(s) for the end use device(s).

Its interesting with all the posts, that no one has touched on the real reason modern vehicles use scores of relays. Anyone that actually knows automotive electronics should be able to easily answer that...

Well see who puts their thinking cap on while I sit back and grab some popcorn.

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post #27 of 35 (permalink) Old May 16th, 18, 7:57 PM
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Re: Where to tie in HEI?

Quote:
Originally Posted by Coppertop View Post
Yes, to each his own.

Whether you take advantage of existing circuits, or create new ones, the responsibility falls on the modifier of said vehicle to make sure the system is safe, reliable and providing the needed condition(s) for the end use device(s).

Its interesting with all the posts, that no one has touched on the real reason modern vehicles use scores of relays. Anyone that actually knows automotive electronics should be able to easily answer that...

Well see who puts their thinking cap on while I sit back and grab some popcorn.
Cost and weight.

With the miles and miles of wiring, it limits the overall amount total amount of metal in the wire needed, which costs less and weighs less.

BTW - when designed 50 years ago, they had a specific use case in mind on these cars. Given all the new gadgets and devices, it is no wonder that the factory style wiring isn't up to carrying the load adequately and needs upgrades and modifications to bring things into the modern world. It's called progress

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post #28 of 35 (permalink) Old May 16th, 18, 8:14 PM
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Re: Where to tie in HEI?

One thing I have found over the years is people not using relays where they should and people using relays where they shouldn't or don't need to.
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post #29 of 35 (permalink) Old May 16th, 18, 9:15 PM
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Re: Where to tie in HEI?

Quote:
Originally Posted by Coppertop View Post
Yes, to each his own.

Whether you take advantage of existing circuits, or create new ones, the responsibility falls on the modifier of said vehicle to make sure the system is safe, reliable and providing the needed condition(s) for the end use device(s).

Its interesting with all the posts, that no one has touched on the real reason modern vehicles use scores of relays. Anyone that actually knows automotive electronics should be able to easily answer that...

Well see who puts their thinking cap on while I sit back and grab some popcorn.
First thing comes to mind is computer outputs on modern cars are low current (and typically are switching the negative wiring on & off). Many of these relays have constant 12 volts on them and the CPU controls the negative side of the relay coils. The relay provides a means to use the low current output to control larger loads.
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post #30 of 35 (permalink) Old May 16th, 18, 9:34 PM
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Re: Where to tie in HEI?

I will add this. With more stuff crammed into smaller spaces, there is less room for high current mechanical switches. and there is less room for bulky wiring, too. So, for something like the various controls that are done by that little turn signal lever there would not be room or current capacity for all the functions, especially high beam head lamps or wiper motors.
Of course others will offer up some more proper examples.
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