NSW Corvettes
Technical Tips => Post 84 => Topic started by: peterw on December 10, 2021, 07:28:27 PM
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My Bose amp relay (ACDelco part 14078902) has given up the ghost and needs replacing.
Has anyone found a local alternative for this?
Don't like my chances of getting one from US before Xmas.
Peter
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My 87 had just a bosch type relay I removed it as original stereo had been totally removed. Just use a relay available from jaycar about $6. Pretty sure still have the wiring I remove. I had to replace a relay on ABS that was defective all I had to do was relocate the negative coil wire in base and was able to use an off the shelf type relay rather than a corvette specific relay. If you need help give me a call
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I know it is a 30 amp relay.
It just looks like any other spotlight relay and I could easily wire another relay to work but it has an extra component wired between the trigger wire and the earth (C and B).
I am not sure what a regular relay would do to the system without that component. I have no training in electronics so I don't know how to tell what it is.
The pics don't show it very well but it is on the wiring diagram. see attached
Pete
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My research tells me it is likely a diode which only allows current to flow in one direction.
What kind of diode and which direction is what I don't know.
I might go to Jaycar and ask one of those young guys.
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Your cct diag is straight forward.
The relay consists of a "NO" (normally open) contactor (A~D) and a Coil (B~C) with a diode connected internally (in parallel) across the coil.
Diodes are always one directional, in basic terms they are rectifiers, they allow the flow of power in one direction, blocking the opposite direction. In DC cct's, like in cars they can be used to absorb back EMF's or voltage spikes generated by the coils when power is turned on or more importantly off. The coil is energised whilst the Stereo is on, upon switching off the collapsing flux generates a massise voltage spike, which can be fed or induced into cars wiring. Not good for electronics.
As Sirfixalot says, a std Bosch auto relay will do the job, watching the wiring, and either internally or externall connecting a diode across the coil wiring - a run of the mill diode like a 1N4004 should do the job. The diode symbol has an arrow feeding into a flat line - this line equates to the white line drawn around the body of the diode.
The Series 2 C4's (90 onwards) use std Bosch style relays and bases in most applications, I suppose GM Engineers had to wake up at some stage and stop trying to re-invent the wheel, to make life hard for its customers.
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PeterW what part of the relay is gone, my 87 of 20 odd years has had aerial issues but never a relay.
Dont throw it away. I'm interested in looking at it, please hang on to it.
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That's fantastic. I think I now have enough info to make a standard relay work for me.
I have tried bridging the power to the amps and it all works fine so the relay is the issue.
When you power the coil on the bench it doesn't respond. I assume it's a short inside somewhere.
American youtubers say that these relays often burn out.
Peter
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Dont throw it away. I'm interested in looking at it, please hang on to it.
Everything I take off the car goes into a box for reference. I always wish previous owners of my old cars had done this.
I'm not going to put the new relay in the standard location, it was a bitch to get out.
The wiring easily goes down to the kneepad area so I will mount it there and make it easily accessible.
Peter
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I have a stack of diodes here as I use them on my C3 electric headlight kits and also a relay can make up something for you I am around tomorrow in Cronulla just give me a call
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Just went to Jaycar. Seems like gone are the days when the young guys in there were electronics enthusiasts and did know stuff.
Guy I spoke to knew less than me, very disappointing.
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Just went to Jaycar. Seems like gone are the days when the young guys in there were electronics enthusiasts and did know stuff.
Guy I spoke to knew less than me, very disappointing.
Like Bunnings, it varies. Some stores have reasonably knowledgeable staff, others don't. Depends a lot on location and the store manager.
What exactly are you looking to buy at Jaycar? If I can find it in the cattle dog, I'll link it.
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I would have thought that if Jaycar had someone who understands electronics the guy behind the counter would have referrred me to him. He just pointed to the shelves and said that's what we have.
Their catalogue has relays but no mention of diode protection.
I have since done more research and now understand diode protection better.
I have ordered a Hella 40a normally open relay with diode protection as this seems like it will be correct.
https://www.hella.co.nz/en/products/relays-flashers/mini-relays-normally-open/12v-4-pin-normally-open-mini-relay-40a-diode.html
A small wiring loom to adapt it to the existing plug and fingers crossed it will handle the current needed for the 4 amps.
I'd be happy for some expert confirmation that this would work?
Peter
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I would have thought that if Jaycar had someone who understands electronics the guy behind the counter would have referrred me to him. He just pointed to the shelves and said that's what we have.
So, you struck a bad Jaycar store on a bad day. The roster can also be a factor.
When it comes to car electrical parts, you may have had a better experience at an auto parts store.
Hella branded stuff is usually good quality. A Hella relay rated to switch 40 amps DC will comfortably handle a 4 amp DC load.
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Cct diag.
Oh! And P.S the fuzes involved are a combination of 10A and 15A, so your 40A relay has contactors well and truly rated to handle the juice.
Out of an 87 EDSM Supplement.
If you got the matching base for the new relay, you should be able to unlock the pins and slide them out and into the new positions in the new base - even though the below pic is for an 87, the wire colour codes etc should be the same.
And I know a reliable member down Cronulla way who has a special tool to get pins out...........
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heres what you need from jaycar relay sy4068 $6.50 , Base if required Sy 4069 $5.95 , Diode Zr1050 100v 3A $3.95 for 10 or get one from me for nothing.
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It's good to have options if the Hella I ordered doesn't do the job. Thanks for the info.
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I have the Hella relay and all looks good except the Hella instructions indicate wire C (85) is for earth and wire B (86) is the 12v wire (pink).
Factory Service Manual shows the opposite. Do I trust Hella or the FSM?
sirfixalot says the FSM does have errors so am betting on Hella being right.
Peter
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The back EMF suppression diode needs to be reverse biased, so in that diagram 85 is earth/ground.
If those connections are swapped, the diode becomes an effective short circuit and will be destroyed in microseconds, if not sooner.
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Thanks, another strike out for the factory manual.
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Replacement relay is in and works perfectly. All this work to make the stereo function, it was worth it.
I pulled the wiring down under the passenger knee pad and cable tied the relay to the loom so it is easy to replace if I need to do this again.
Thanks to everyone who responded especially sirfixalot who contacted me and offered to make me a relay.
Cheers
Peter
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Well done looks professional with heat shrink on joints and tape around relay base