Tachymetric relay .... which?!

[soundguy 14]

I saved this note after looking into these a while ago - additional info that might help, if the supply of M+D dries up 

 

HELLA 4RP 008 189-111
HITACHI 95.496.621
OE 95496621 - CITROËN / PEUGEOT

Durite 072342
Lucas FDB 506 (+505)
Cartier 02474

[SRDT 242]

So the relays from M&D (422011), ERA (661136) and HERTH+BUSS ELPARTS (75614042) all looks exactly the same and are branded WEHRLE 51 223 909.

You just have to pick the cheapest brand, let's hope that it stays in production longer than the others.

 

Now it's not exactly the last one because there is another potential replacement : KAE 3.304.500 used on BMW to replace 0280230001/0280230005/0280230016.

 

From south America there is also Ralux T-8582 in Argentina or DNI 0336 and ARPE RT200 in Brazil.

 

 

On top of that there is a shop in Hungary that is making solid state VW/Audi/Porsche relays that are close but not directly compatible : 

 

https://norx-electronics.hu/?page_id=12177

 

If other manufacturers cease production it should not be too hard for them to add center pin 87b and to remove the fuse holder on their 477 906 059 relay.

[bacardincoke 48 1 Cars]

What a minefield!

 

Baptiste... maybe one for you to run your eye over, it being a French forum and my having to rely on Google Translate may end up in mistakes.

 

https://www.planete-205.com/forum/difference-entre-deux-relais-identiques-ou-presque-t66392.html

 

Are they saying - there are 2x types of identically pinned relays, however ones circuitry subsequently had a diode included, the reasons are given if you trawl the various posts / links quoted and if true worth considering..

 

The main visual difference I can see (looking at actual relays and the schematics in that post) is that the earlier version has one of it's pins marked '1', while the later version has the same pin marked 'TD' instead (all else is identical).

 

I've read elsewhere that those relays with the '1' pin take their signal from the coil, while those with a 'TD' pin, it's the ECU... again, quoting the inter-web so to be taken with a big pince of salt.

 

It's been suggested that may result in the fuel pump priming for a lot longer on one or the other / not priming at at all unless certain cranking revs are achieved?

 

There's other stuff I've written down and more questions as a result, but will limit things to this for the moment... my heads already pickled enough!

 

 

 

[DamirGTI 362]

I'll try ..

 

In electrics with inductive load , when 12v supply gets switched off it tends to create high voltage spike (several hundred of volts for a milisecond or so..) , and this (back) voltage spike will be on reverse polarity to the supply and can zap contacts and stuff in that and associated circuts .

So the diode is used to snubb that back voltage spike .

 

It is "improvement" over previous design .

 

TD was just some fancy German name for tacho signal , tachodrenzzzhughhanuung....something ..

Edited 2 hours ago by DamirGTI

[SRDT 242]

What is strange about the diode is that each relay is powering the same kind of things on a Jetronic engine so it's not like there is a particulary big inductive load for a specific relay.

 

As for the Peugeot part numbers I found a Peugeot Motors of America document and 6555.22 is indeed used on the 1985 505 turbo with no intercooler (N9T), by 1986 it's 1452.05 and the engine is intercooled (N9TE).