RPM relay burned

[john 05141]

Hello y'all

While in the fusebox area, I noticed a burn stain on the plastic connector of the RPM relay.
I did notice the engine was not running quite right just previously.

See the pictures. It is the white-purple wire that burned half an inch before it reaches the relay. In the relay I noticed the burn smell and also I could pry loose the track on the pcboard easily probably becasue of the burn.
I opened up the fuelpump access panel and memoved the dust cover. All seems normal there and no wired damaged or burned. Interiaswitch, do not see a burned wire there either and the switch works.

Anyone had this experience and found what went wrong?
I ordered a new relay and its connector.

Jan286922869328694

[Bitsyncmaster]

The white/purple wire supplies the fuel pump power. Where did you get that RPM relay? I have never seen that unit here in the USA. Surface mount components on the bottom and a blue connector. I would measure your fuel pump current to be sure it's less than 10 amps (engine running).

Depending on the copper thickness of the circuit board, it looks like that circuit board trace is to narrow to carry 10 amps of current without overheating.

[john 05141]

Hi Dave,

Actually this is nbr2.
That one came from the Delorean serive center in Belgium that gets those from DMC EU
as this one was burned, I got another one, and it is exactely the same one.

Jan

[Bitsyncmaster]

I see a red fuse in your photo. The fuel pump should be fused at 20 amps. Not that a 10 amp fuse would cause the burning at the RPM relay but that 10 fuse would run hot.

[john 05141]

Oh, you mean under that clear plastic cover?
That is a fuse for the fog light. Never used it one, but necessary to pass inspection.
Fog is common here in winter times, when the Delorean is then in winter storage.

Jan

[Bitsyncmaster]

I saw the normal fuel pump fuse removed from the fuse block and a red fuse was sitting on the back shelf. Here in the USA a red fuse is 10 amp but I see some of your fuses are not marked. I also see a you have a black fuse which I've never seen before.

[john 05141]

Oh, OK now I follow.
The fuse in the fusebox has burned before obviously, but I never made that bypass.
The red fuse you see comes from the doorlock module, not from the bypass.
My alarm system is acting weird and the hazard lights are activated. I am trying to shut it off but no matter which fuse I pull the problem remains. I was hoping this fuse would stop that but it does not.
I will follow the wires from the siren this evening, and I heard this unit might be behind the shelf.
So I am not nunning a fuelpump with a 10A fuse, but thanks for noticing

I have restored the electrical connection to the RPM relay, and I will be making a new ground wire from the inertia swich today to hopefully tackle the problem because I still do not know why this occured.
I started the car yestrday and on idle it runs fine. Terrible weather here nowadays I do not want to take a road test now.

Jan

[john 05141]

Got this aftermarket DMC relay built in, + replaced a new connector so everything is back as it was.
Still I have no idea if this problem was there already but on Welmoed's advice I made an extra ground connetion from the inertia switch.

So this weekend I made a test drive with the the elctrical compartment uncovered and the RPM relay "availabe" in top.
After 15 min this relay gets pretty hot. I can still hold it with my hands, no risk of burns but it feels pretty darn hot. The cables remain cool and no burn stain appears like last time.
But I am not sure if it is supposed to get this hot.
I made the return drive, again 15 min. same thing. I had a close look afterwards and visually allis good, just this relay gets hot.

Welmoed told me Dave has a version that stays cool. You still sell those?
Jan

[Bitsyncmaster]

Got this aftermarket DMC relay built in, + replaced a new connector so everything is back as it was.
Still I have no idea if this problem was there already but on Welmoed's advice I made an extra ground connetion from the inertia switch.

So this weekend I made a test drive with the the elctrical compartment uncovered and the RPM relay "availabe" in top.
After 15 min this relay gets pretty hot. I can still hold it with my hands, no risk of burns but it feels pretty darn hot. The cables remain cool and no burn stain appears like last time.
But I am not sure if it is supposed to get this hot.
I made the return drive, again 15 min. same thing. I had a close look afterwards and visually allis good, just this relay gets hot.

Welmoed told me Dave has a version that stays cool. You still sell those?
Jan

Yes the original RPM relay runs very hot normally. It's the high current in the relay coil that produces the heat.

Yes I still sell my solid state RPM relay which runs cool. It uses MOSFETs to replace the relay and a micro-possessor to control the logic.

[Tillsy]

and a micro-possessor to control the logic.

Is its name Zuul? :)

[Bitsyncmaster]

Is its name Zuul? :)

I use PIC micros on my DeLorean products. Using software lets me add additional functions not incorporated into the OEM design.

[john 05141]

Dave,

I'm interested in one of those. All your stuff is super.
Is it just plug and play or what has to be done extra?
Price?


Jan

[john 05141]

From the classic relay, can someone describe how hot the standard RPM relay is supposed to be after a drive ?
very hot, but you can still hold it, like a cup of coffee
very hot, if you squeeze the RPM relais feels painful in your hand but nothing melts,
wondering if it is about the melt at any time, like a fresh cup of coffee in you hand,
I'm on fire....

I am going with Dave's solution anyway.