RELAYS

I'd replace/upgrade the fusebox before I even started looking at the relays, but I'd be interested in higher reliability replacement relays, even though I've never had one fail.

 

The mini's were never really a problem. Many of the 80's cars are still running around with the originals, still trouble free. The micros are a real problem. I keep a bunch here on hand and replace them regularly. Brand has not seemed to matter. It seems the small, lighter gauge wiring and minimalistic relays are just here to stay for costs sake. Cost savings in electrical components, especially in cars that are more dependent on it than ever has really compromised the long term viability of cars. The industry wide plan to switch over to a higher standardized voltage for passenger cars has been put on hold due to the inability of much of the cheaply made componentry to cope with it. They are caught on the horns of a dilemma.

Cars from the 60's, 70's, and 80's will be around running long after the Kleenex generation cars are long gone. I like the modern tech in cars as much as the next guy but it is just not built to last. For most cars, that's OK. Throw them away every few years and get another but in the case of Ferrari's people want to keep them around a while. Everyday it makes me happy I am nearing the end of my tenure doing this and not the beginning or I would have put plan B into action long ago.

 

Sounds like a great idea, and shouldn't be too difficult for the standard 2 low power pins to complete the high power circuit type, but I know on the 348 for the ABS system there are 3 relays that are each specific to their applications with no substitutions. Knowing Ferrari, there are probably many other cases of weird only-made-for-this-model relays that may be impossible to replace.

 

Carl, you know my feelings on this. Get the high current loads like the fans & fuel pumps off the main fuse/relay board, then replace all the relays every 5 years or so. $25-$50 for peace of mind is chump change.

The high current loads need their own dedicated feeds, and the radiator fans need 75a relays. Ferrari may know their engines, but they don't know squat about electrical systems.

 

I don't know that SSR's are the answer here because they don't have the form factor that we need for plug-in replacements for the Bosch's.

Most people never worried about replacing relays in the past because their lives were usually greater than a million operations or so. But with higher amperages and higher spike levels, those lives are reduced quite a bit. This is why we now ought to consider relays as consumable items that need to be replaced periodically, like timing belts.

Do you know that in the electrical world, fuses are now considered wear items and are recommended for periodic replacement? It's true; high voltage fuses that have operated at, or near their rated interrupting ability are considered to be "weakened" and are now recommended to be replaced periodically. This philosophy hasn't trickled down to the 12v automotive world just yet, but there's no reason for it not to.

 

At what point do you just bite the bullet and go to a PDU/PCM (Motec, Life Racing, OBR, etc.)? Worse than the relays are the multilayer fuse panels.

 

Those modules are an interesting solution for people who are building "new" cars, racecars, or kitcars. But I don't believe they're viable for the retrofit market that we find ourselves in.

I really do believe the most effective path to increased reliability of these main fuse/relay boards is:

1. Get the high current loads out of the main fusebox/relay board and onto dedicated feeds

2. Replace the existing relays periodically

3. If/when possible, insulate the footwells and engine bay in front of the footwells.

 

Right, any electrical component that has to make or break live loads are going to wear, no way around the physics of it. Fuses and resistors are also going to have a life cycle as the metal employed cycles thru micro-fatigue from heating/cooling thermal stresses.

Automotive circuits as much as we like to think of them as DC are not true DC when the alternator is on-line. there is a ripple in the current and voltage, add in transient spikes from switching live loads and components are going to eventually fail, esp those with diodes in them. The battery while only having a potential of ~13V has a massive amount of current capability, that is why contact relays take a beating, micro welds every time it's cycled.

I'd be more concerned with the fuse panel mylar and cold solder joint fatigue, toss in the undersized wire gauge and bad grounds, corrosion at the terminals and when current goes up due to increased resistance.. melted insulation and burned out contacts. The battery has more then enough capability to weld all the terminals in a vehicle.

 

That would depend on the relay, being that it's an electromagnet it doesn't really rely on permeability of it's core. If it did then heat would effect it's ability to hold the circuit. There's probably more heat generated within the back EMF resistance and transients then external ambient heat.

If the relay has circuit components of diodes or film resistors then heat can become an issue.

 

Feel your pain, but SSRs have some downsides that are virtually unacceptable for a car -- they are "leaky" when off (so the battery would be deeply discharged overnight), heavy, and need a lot of cooling (especially if you had 10~15 of them in the same space) = big heavy heatsinks and probably some air fans too. The little electromechanical relays aren't perfect, but they make a lot of sense for a car.

 

Furthermore SSRs do not galvanically isolate the load circuit. There's "only" a switched off semiconductor, not an isolating air gap.