40 amp power relay has a resistor that may prevent blown fuses.

What is the purpose/benefit of the bracket?

 

I can not see how the resistor can prevent blown fuses.

It should have been a diode used to limit the generated high voltage when deenergizing the coil. Sometimes a resistor is used since it has no polarity requirement, but a resistor is not as good as a diode.

The real benefit with a diode/resistor across the coil is that it prevents arcing (and premature failure) of any relay or switch used to energize the coil.

 

Am I reading this wrong? The resistor is across the coil in the relay and has nothing to do with the circuit that is activated by the relay closing?

 

From what I see in the diagram, that is correct - the resister has nothing to do with the load in the circuit being activated. Therefore, if you are using this relay where the circuit involved still passes through the fuse, there wouldn't be any difference in the instantaneous load across the fuse when the relay is activated.

 

Just to answer on the diode thing, it does not require a large diode to clamp the excess voltage across the coil. But, a resistor is cheap and may have a longer service life than a diode.

 

Since the resistor only reduces the power going to the coil, adding this device is increasing the electrical load on the system. Where you used to have, say, a motor that when turned on, drew X watts of power through a fuse, now you have that motor AND the relay's coil drawing power through that fuse. So you have added the power drawn by the relay coil to the circuit load. Frankly, it increases the chance of blowing a fuse! Of course, it is entirely possible that installing one of these reduced blown fuses because in the process, wiring/fuses/contacts/whatever where cleaned up. Did the OEM fuses create problems when these cars were new? It seems like they are a problem now, 30+ years later but were folks constantly taking their new 308's back to the dealer for electrical work?

FWIW, if you add the relay coil to the original circuit but remove the motor's load and place it (through the relay) on a new, properly sized/fused wired circuit, that's a whole different deal.

 

Yeah, on our old cars, this resistor thing is too late to add anyways. Years of arcing in the headlamp switch has already happened ...

I noticed on one relay that it was 680 ohms in parallell which would add as much as 18 mA of current when the relay is active. I would not worry about it.

 

+1 -- Keeping careful, and consistent, control of what's on terminals 85 and 86 would be a real challenge -- IME, Ferrari often even has the wires physically switched on those two terminals in the as-built condition vs what's shown on the schematic

 

I fail to see how a resistor on the solenoid voltage circuit has any effect whatsoever on the current flow for the load itself. At best, it's only going to protect the relay from damage.

 

+1 - this sentence: "the internal resistor protects sensitive equipment against voltage spikes" is very misleading. It means: "the internal resistor protects sensitive equipment actuating the relay against voltage spikes that occur when the relay un-actuates" -- not that the resistor is beneficial for the load side equipment in any way.

 

EXACTLY!