Tachymetric relay .... which?!

[soundguy 15]

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 249]

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 August 14 by DamirGTI

[SRDT 249]

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).

[DamirGTI 362]

Indeed , not as much load as some other stuff say like AC clutch ..

 

But there was cases of those relays burning on the pins and even catching on fire , years ago i had that on my Ph1 205 with the relay mounted underneath the battery , something went wrong and it caught on fire while driving .. luckily i spot it on time otherwise it could've taken entire engine bay in flames ! 

Once i had split/cracked diode too , no idea why , replaced the diode and it never happened again . 

Maybe it's the fuel pump which sends back voltage spike whilst switching off ?! 

[SRDT 249]

Some cars have a priming pump inside the tank and a main pump outside so that could be seen as extra load for the relay, that's the case for the 505 and yet Peugeot was fine using the 1452.05 relay.

 

As for the TD pin it could be for a more "proper" speed signal unlike the spike from the ignition coil, in fact even Peugeot could have used the signal from the diagnostic speed sensor.

[bacardincoke 48 1 Cars]

Went down a rabbit hole last night... so much contradictory info. to sift through.

 

The following is how I've it straightened out in my head, but worthy of note is that very little of it can be backed up by direct references that I can point you towards.

 

For example there may not be a black and white list stating X or Y fits this or that, but because that something isn't on the list it can be inferred it does, clear as mud!

 

I'll start at the beginning, so probably re-stating some of what has gone before, but for the sake of completeness... 

 

1452.05 is the original relay (if excluding the very early Phase 1 / engine bay fitted one).

 

It appears to be prone to early failure.

 

An improved relay, 6555.22 with circuitry that included a freewheeling diode to prevent spiking and therefore damage replaced it.

 

I use the word 'replaced' for a reason, it seems 1452.05 was withdrawn, not merely superseded... meaning it was no longer made and shouldn't be used (presumably because it'd ultimately fail again).

 

Bosch occasionally did something similar with various unrelated K-Jet components, one that springs to mind are certain accumulators for some early Mercedes.

 

They turned out not to be up to the job and withdrawn / no longer made / existing stock not to be used, with an improved version (different part number) was all that was available / to be fitted.

 

1452.05 will have the '1' pin I mentioned before and 6555.22 the 'TD'.

 

6555.22 is backwardly compatible with 1452.05.

 

That'd take care of things back when genuine relays were still available, say from a dealer.

 

I think this is where the current day confusion starts.

 

If you check a present day, re-manufactured relay that's catalogued (inadvertently, rightly or wrongly) as compatible with 1452.05 and it's for a vehicle that's listed as requiring 6555.22 you'll be told it isn't suitable when in reality it will be.

 

More twists... the Wehrle 51223909 (Meat + Doria 422011) relay is catalogued as replacing 1452.05, which is why it's showing as unsuitable for my 1989 car when the reality appears to be it's made to 6555.22 standards / is suitable (that'll need confirming though, relying on unchecked info.)

 

Interestingly M+D 422011 has a '1' pin and listed as unsuitable for my car, but they also make / made an otherwise identical relay 422040 with a 'TD' pin that is listed as suitable... plot thickens.

 

Rambling on now, will stop there other than to ask can someone who has the M+D 422011 in a post 1989 car confirm it works fine?

 

PS. I've also read that the original Bosch versions, which includes 0 280 230 006 will prime the pump for a few seconds on initial key / coil signal, whereas other makes don't necessarily, instead waiting for an additional starter cranking signal.

 

 

 

 

 

 

[DamirGTI 362]

Take aftermarket part No's and reccomendations with pinch od salt ..  especially Chinese ..

Certain components can be used on various makes/models of cars and relays are one of them .

 

Lately i've seen quite a few new relays switching from combine electro mechanic to fully electronic so only micro components mosfets etc .. flasher relays , heated screen timer relays and so on .. 

 

Haven't bought any od those 7pin fuel pump relays so not sure , but you'll notice by much less weight of the relay that it's fully electronic .

 

From the past experiance most of the issues occurs because of the loose and dirty/oxidized relay connector terminals .. if you clean and "re-tense" these most of the time you'll be fine .. as loose connection = heat ..

By far the worst are any electrics situated in the engine bay and outside of the cabin cause of moisture heat vibration .. 

Thats why they swapped places of the fuel pump relay from the under the battery mounted Ph1 to into the cabin on Ph1.5/2 version ..

Edited August 16 by DamirGTI

[bacardincoke 48 1 Cars]

In fairness to them it's looking like the Tecdoc and similar databases that  Autodoc / others rely on is corrupted insofar as these particular relays are concerned and throwing up false info. as a result.

 

Seems plausible that it stems back to the cataloguing of the replacement of / switch from 1452.05 and 6555.22 .

 

When Wehrle and others then catalogue their current day relays against the old number, when they should more properly use 6555.22, it just throws another curly one into the works and confuses things even further.

 

You mentioned elsewhere successfully using a relay listed for Vauxhall / Opel's?

 

Don't be taking it out to check etc., but if you'd the number recorded somewhere it'd be useful... have found some Bosch specifics that may confirm what exact one (possibly yours) works / would potentially make it in the running for another alternative if I can confirmed it.

 

 

 

 

 

 

 

[DamirGTI 362]

Yes , one from the Opel Kadett 1.8 or 2.0 Gsi .. i found decades ago on a scrapyard and since then i've been using it too on a daily driven 205 up until reacently so quite a lot of years .

Cannot recall part No , there where some Opel numbers on it .. 

BMW ones will work too for sure , as well as Fiat group , Volvo and some orhers . 

 

Do not worry so much about it ! , if it phisically fits the 205 7pin socket 9 times out of 10 it'll work regardless being Opel Fiat or Volvo item .. 

 

If you fancy experimenting and have sensible priced scrapyard near with bits for cars from the 90's , see if they have some 7pin relays for play ..  

[SRDT 249]

Here is the 1997 Peugeot document with both 1452.05 and 6555.22 listed meaning that at least back then the two parts where not equivalent enough to replace each other.

 

http://peugeot505.info/photos/gal/Manuals/505_1997_qrpm_turbo/505_qrpm_turbo_069.jpg

 

There is also this Servicebox rip from 2012 with 1452.05 still listed for the 205 :

 

Link here

 

And now for even more strangeness there is yet another tach relay for the 505 and it's 6555.47 or 0280230014, i can't find anything in the old parts catalogs but Peugeot Classics still has one to sell : 

 

https://www.boutique-laventure-association.com/en/peugeot/9534-flashing-unit.html

 

They say "flashing unit" but the picture and the Bosch and Peugeot part numbers are those of a tach relay.

[bacardincoke 48 1 Cars]

I've identified a few Bosch numbers from the 0 280 230 *** family that cross reference with what we're after, some directly but with others it's a bit convoluted.

 

Trouble is, like you say, apart from  run of the mill Volvo / Opel / Vauxhall ones (surprisingly expensive), there's some BMW's, such as certain E28's, Alfa Spiders, even Ferraris that also use them (very expensive), so a bit of a dead end if we're looking for a bargain.

 

Petert'll already know this, Australian Holden Commodores might also be a source of original 1452.05's (Wehrle even list 51223909 for them)... suppose it's because of the GM / Opel / Vauxhall connection?

 

The main differences I can see in the Bosch 7 pin versions (with the Peugeot pin pattern) and that might interchange with one another is what they call the 'Fall time' of each.

 

Basically how long they are set until they turn the pump off with the ignition / a rev. drop below a certain limit / collision etc.

 

It's literally 10ths of a second differences, one may be 0.2s and another 0.5s... hard to understand why there's the difference, let alone the significance of what appears to be such a tiny amount, but it appears to matter / differentiate one number from another.

 

Baptiste, I found a reference about 6555.47 on a 505 forum, the poster was talking about the US version... I've no way of immediately finding it again unfortunately, didn't think to bookmark or think it might be relevant at the time. 

 

0 280 230 014 though makes an appearance in some of the Bosch stuff I've read, 016 likewise. 

 

 

[DamirGTI 362]

Only difference that i can think of is priming and no priming with ignition ON , diode protected or not , and slight difference in fuel cut off revs .

 

So 80's/90's cars which used Bosch engine management and where on distributor pick up coil ignition are potential source of the working fuel pump relay .. 

[DamirGTI 362]

6 hours ago, bacardincoke said:

Don't be taking it out to check etc., but if you'd the number recorded somewhere it'd be useful..

I found some old pics , it's : 

 

90158189

 

So that one just primes for a second od so with the key ON .. 

[bacardincoke 48 1 Cars]

90158189 is confirmed as a GM / Opel / Vauxhall part number... Ascona C / Kadett E / Manta B / Rekord A / Senator A if you ever come across any of those in your travels would be worth a check.

 

Subject to better confirmation, it's looking like that's an equivalent of Bosch 0 280 230 006 and as Baptiste says therefore also of 1452.05 (so should have a '1' pin).

 

Just speculating here... if it's true that Bosch relays will prime on the first turn of the key, but the Peugeot ones that aren't from them don't (eg. Cartier) would seem to suggest yours is maybe the former.

 

The Lucas versions of the Peugeot compatible relays are showing as not priming on the key... I'm starting to think Bosch made the Lucas ones, it must be more than coincidence that DFB505 matches Bosch 005 and DFB506 Bosch 006.

 

There's a DFB501 which may also fit 205's and is the equivalent of Bosch 001, so would be following that same pattern if true.

 

If we're going to accept the Lucas / Bosch are one and the same then it appears the only difference I can find between them is the shut down times, all else matches.

 

DFB501/001 is 0.5s (GM/Opel/VX)

 

DFB505/005 is 0.1s - 0.5s (Citroen/Ferrari/Fiat/Lancia/Peugeot/Seat)

 

DFB506/006 is 0.2s - 0.6s (Citroen)

 

The makes in brackets are what Lucas would say their relays are for, however I've seen images of their Bosch counterparts that cover others as well, for example 001 is for BMW's and Alfa's.

 

I've written quite a bit of this down and can leaf back and forth through it and it's still giving me a headache trying to follow it all... it's just a mess, for anyone reading this don't be rushing out to buy any of the relays I've been rabbiting on about, most of it's semi-informed guess work using untested / contradictory references!

 

 

 

[SRDT 249]

6555.22 is listed in many places as Bosch 0280230009 and that one is confirmed to be Citroën 95496621 from the 1983 CX 2500 GTI (at the time Citroën wasn't using Peugeot part numbers yet).

 

0280230009 is a blue relay with a "TD" input and it is also used on the Alfa 75 turbo. Both the CX and the 75 are running LE-Jetronic injection with a (different) fancy ignition ECU that is directly driving the injection ECU instead of using pulses from the coil. Both are also feeding this "not the coil" ECU signal to the blue relay. The 75 still has one coil and a distributor but the CX has wasted spark with two coils so there is no easy way to drive any other off the shelf tach relay.

 

The Euro 505 turbo N9TEA is using the same EZK ignition than the Alfa but they drive their 0280230006/1452.05 relay with the coil like the older non-EZK Euro 505 turbo. It seems than the US 505 turbo had EZK ignition from the start and on the first year used the fancy dedicated tach relay before switching to the more mundaine (and likely cheaper) 1452.05 relay.

[bacardincoke 48 1 Cars]

That interesting, touches on what I mentioned and must've read somewhere about the 'TD' pin denoting it was intended for ECU signals and the '1' pin was for coils, though from what you've found out it doesn't seem to be an absolute thing either and some can handle both?

 

I suppose the main reason I took more of an interest in this was to hopefully find alternative (read that as either more easily found and / or cheaper) relays... but looking at the prices of those that we have identified and are for other makes, it's if anything worse.

 

In fact, I wonder do owners of E28's, Uno Turbos etc. realise it probably works the other way about and they can likely get what they're after easier / cheaper by looking for 1452.05 / 6555.22's instead?

 

The M&D 422011 relay is at the time of writing down to £29.99 on Autodoc (via the app, not the website), but postage will bump that up (another £8.50 if the total bill is less than around £135, otherwise included free).

 

It's still showing with them as not suitable for my 1989 car (Opel's instead), but if you dig down through the tabs further they also mark it as compatible with 145205, which just goes to reinforce further what a misleading mess the numbers seem to have become.

 

Not a waste of time though and as Damir says if you've the luxury of being able to scour some scrap yards it may just get you a bargain, unfortunately on-line not so much from what I can see.

 

Judging by the links to most of the numbers mentioned in previous posts, Wehrle seem to be pushing their 51223909 as suitable for nigh on everything, perhaps modern day electronics allow for that. hope they're right.

 

Hopefully too that means it's going to be worth their while continuing making them, all the other aftermarket manufacturers seem to eventually stop... think I'll be planking one of there's away, just in case they dry up too some day.

 

 

[ALEX 103 1 Cars]

On 8/16/2026 at 1:51 PM, bacardincoke said:

 

 

Rambling on now, will stop there other than to ask can someone who has the M+D 422011 in a post 1989 car confirm it works fine?

 

 

 

 M+D 422011 works fine for my 1988 (F) Phase 1.5 205 CTI. I can't see why it wouldn't work on 1989 or even Phase 2.

[bacardincoke 48 1 Cars]

Great, thanks... it's all very well me speculating about this or that, but to have it confirmed in reality is the important thing.

 

 

 

 

[lagonda 42]

Many thanks for all replies, very interesting. Been recommissioning my latest car purchase past few weeks in the UK hence only just reading all this now.

[bacardincoke 48 1 Cars]

Was reading something last night that reminded me of this thread... might have to revisit some of what I thought I'd understood as correct.

 

Hasn't stopped niggling me why some sources say one particular relay is compatible with my 1989 phase 1.5 1.9, when another says it's not.

 

Going to run this past you, see if anything sticks with those who better know these cars, I'm still very early days.

 

Harps back to that '1' and 'TD' pin, it may matter more than first thought.

 

Seems it is as we thought and '1' is for a signal from the coil and 'TD' an ECU, though it's a bit more than that.

 

Think I'm right in saying the 205's ECU doesn't directly signal the relay, it's the ignition module instead?

 

The interesting bit is the module seems to have changed at the same time as the relays did from 1242.05 to 6555.22.

 

MTR01 modules are generally 6 pin (can come back to that if necessary, there seems to be exceptions) and MTR02 7 pin.

 

If present Pin 7 sends the signal to the relay, not the coil.

 

1242.05 needs MTR01 / coil signal to work correctly.

 

6555.22 needs MTR02 / module signal to work correctly.

 

I've read they're not interchangeable if true.

 

Miamistu and some databases (Autodoc for example)  quote 12/1989 as the cut off dates for the modules.

 

Does that anyway coincide with the coil moving to the intake manifold?.

 

My car's June'ish 1989 with the MTR01 6 pin module, can't get in it to check the relay unfortunately, would've been useful, but I'm being told i need 6555.22 when it's age and module suggest 1242.05!

 

Of course things may have been changed out over the years, so not a given either.

 

To add to the mix is that M&D 422011 is listed as replacing 1242.05, not 6555.22 (M&D say 422044 replaces that) and it too isn't for my car.

 

Alex's car runs with 422011, but it's a 1988 so well before the cut off / not in doubt it takes the earlier relay.

 

Can someone with a post 12/1989 car (or even one with a MTR02 module) check that 422011 works OK?

 

 

 

 

 

 

 

 

 

[bacardincoke 48 1 Cars]

*Substitute 1452.05 for 1242.05

[SRDT 249]

12 hours ago, bacardincoke said:

Think I'm right in saying the 205's ECU doesn't directly signal the relay, it's the ignition module instead?

The module is driving the coil, it's the voltage spike from the coil that is driving the relay, tachometer and L-Jetronic ECU.

 

On 8/28/2026 at 12:03 PM, bacardincoke said:

Miamistu and some databases (Autodoc for example)  quote 12/1989 as the cut off dates for the modules.

Miamistu only has one GTI ignition module (5945.48) and I can't find any trace of 6555.22 there. Only 1452.05 and 1452.10, the older relay with rev limiter.

 

The 7 pin module can simply replace the 6 pin one so Peugeot didn't need to change the part number even if they wanted to use pin 7.

But Peugeot at the time was quite conservative, on the 205/309/BX/405mk1 they where still driving the tachometer with coil pulses even when the ECU had a tach output. They only used it on wasted spark ignition engines because there was no other choice.

[bacardincoke 48 1 Cars]

Apologies Baptiste, have been attempting to reply since your post, but I'm struggling to get onto the Forum... just continually times out, or if I do get as far as the index page, that's it.

 

I read this on a Fiat forum, a very old thread... my understanding of it was that someone was asking much the same questions I've been.

 

I hope I remember this correctly, it was a week ago now, but if so the gist of it was that MTR01 modules with 6 pins (pin 1 of those) as you say drives the coil via it's -neg post.

 

The relay's with a 1 pin tap into that feed (externally at the coil, not directly from the module) and use the high voltage (300 - 440v) raw spikes produced.

 

MTR02 modules with 7 pins (pins 1 to 6 function identically to those on a MTR01) still drive the coil via their pin 1, but instead also create a square low voltage (12v) signal internally within the module which is transmitted to the TD pin of a compatible relay.

 

It was said that using a TD relay with a MTR01 module could result in the relay simply just not working as it couldn't read the different type of signal or it even being fried as it's internals aren't strong enough to receive such a high voltage.

 

Conversely a pin 1 relay inserted into a set up that is intended for a MTR02 module (ie. there will be no high voltage external feed from the -neg coil to the relay) may not be able to read the low voltage signal, it'll not damage this time it but it'll not be able to read the signal / not work.

 

As an aside I've read elsewhere that a 7 pin MTR02 module can be fitted to a MTR01 6 pin set up (ie. it will have the external -neg coil feed for the relay) and will work correctly... it's just a case of pin 7 on the module not being connected to anything (the female plug doesn't have a corresponding pin) and it's effectively dead.

 

If any of the above bears out, it would explain why the databases work they way they are... what do you think?