Relay, low fuel delay module, *089M6330F

[swindon_alan]

INFO
Lotus description: "Relay, low fuel delay module"/"Low fuel warning lamp delay module"
Lotus part number: *089M6330F
Manufacturer: BMI
BMI part number: 01212E
Cross references: None, specific to the Esprit
Status: Obsolete, SJ Sportscars, the Elise Shop, etc. may have stock

PHYSICAL

BOARD LAYOUT

COMPONENTS

CIRCUIT DIAGRAM

FUNCTIONAL DESCRIPTION
"Low Fuel Level Tell Tale: This lamp is calibrated to light up amber when the level of fuel in the combined tanks falls to approximately 10 litres (2.2 imp. gal; 2.6 US gal). Note that the fuel gauge will be reading zero at this time. The level sensor is combined with the fuel gauge sender in the LH tank."

The module smooths out any temporary movement of fuel in the tanks to provide a stable tell tale illumination.

COMMENTS
This feels like a lot of electronics and probably overkill to provide some hysteresis around preventing the tell tale coming on when temporarily accelerating/decelerating/climbing/descending/pulling Gs around corners (and conversely to latch on when "properly" triggered). But then this is a Lotus :-)

WORKAROUND

Jumper wire:

LOW FUEL WARNING LAMP TEST

Jumper wire:

[Erikl]

I was installing the ABS delete kit on my 94 and I hit this with module with my elbow and broke it 😞

JAE here in the states does not have one - S&J show one but I have not confirmed.  Thanks for posting the work around - going to give this a try and see how it goes.

[march]

Has anyone thought of wiring one of these into the old relay body. Seems to do the same thing.

https://www.ebay.co.uk/itm/Low-Fuel-Warning-Delay-Switch-Relay-Fits-Triumph-TR7-TR8-BDS1003-00-/352502185452

 

[swindon_alan]

Interesting @march. It has four terminals, T, L, B and E. Presumably Tank, Light, Battery and Earth? That's the same arrangement as the BMI module. So possibly... However, we would need to see it in the context of the wiring diagram. The Lotus uses a separate switch in the tank to signal that one, whereas this one might use the variable voltage off of the fuel level sender.

The part number, BDS1003 also covers BDS1004 by the look of it and the description on an ad reads:

This is a NOS Smiths thermal delay switch, or low fuel warning relay for Triumph TR7 and TR8 . Smiths Part number  BDS 1004/00.

That tends to suggest that it is switched.

 

[march]

1 hour ago, swindon_alan said:

we would need to see it in the context of the wiring diagram

Will scan the manual tonight. The tank line comes from a switch on the fuel sender if I remember correctly. I assume being an old Leyland part it is going to be pretty dumb.

[march]

@swindon_alanThe scan shows 99 being the low fuel delay relay, 98 is the tank sender unit.

 

LGR feeds the low fuel light via relay switch.

 

I may even have one of these lying around should anyone wish to prove this.

 

[Erikl]

Hmm Maybe I will buy it and have it shipped to Alan so he can take it apart.

Odd, I have my module unplugged and out of the car.  I was surprised my gauge worked at all.  The gauge moves a bit when going around a corner but its barely noticeable.  I have to put the bypass wire in and see how it acts.

[march]

This module does not affect the gauge at all, just the low fuel light.

[Erikl]

Ohh wow - that is a lot of extra just for the light.

Sometimes I am amazed at the hoops auto makers have to jump through to deliver something like a low fuel light that you never think about or take for granted.

[ekwan]

If the Lotus fuel sender has a separate switch for "low fuel", a simple delay circuit using the NE555 timer could provide say, T=3s (more or less) damping for the fuel light. Cheap and uses the minimum of components.

Edited May 31, 2019 by ekwan

[Erikl]

The NE555 is less than $2.  Can you get a socket that it fits in that allows easy attachments with short leads?

 

https://www.frys.com/product/8052424?store=38&source=google&gclid=Cj0KCQjw_r3nBRDxARIsAJljleFDxTz-vTv92ydjhuQvJpPaDO7JntSK546-5-tzYv7MVpfGWsUdd74aAv_2EALw_wcB

 

 

[swindon_alan]

9 hours ago, march said:

@swindon_alanThe scan shows 99 being the low fuel delay relay, 98 is the tank sender unit.

LGR feeds the low fuel light via relay switch.

I may even have one of these lying around should anyone wish to prove this.

That will do the job @march. As you note, a separate switch in the tank in the TR, same as the Esprit. I would have to get a meter and a 12V supply on one to confirm the pin outs but yes, very good spot. Depending on the size - you might have to pull it out of the can - it could even fit in the BMI shell with some short jump wires, as you suggested. It would swap electronics for electro-mechanical but as I noted above, "This feels like a lot of electronics and probably overkill". @Erikl indeed you could build a NE555 version of the BMI but you would also need timing capacitors/resistors and a power transistor or a relay to ground the 12V feed from the warning lamp.

 

[march]

@swindon_alan I have half a dozen old TR7 wiring looms, I will see if one is still attached for you to play with (if it's not practical let me know as these seem to have some value - although I have never heard of one failing), will let you know over the next few days.

[swindon_alan]

Thanks @march, yes let me know if you find one and I will PM you my address. I can send it back to you again after examination. Good stuff!

[ekwan]

2 hours ago, swindon_alan said:

That will do the job @march. As you note, a separate switch in the tank in the TR, same as the Esprit. I would have to get a meter and a 12V supply on one to confirm the pin outs but yes, very good spot. Depending on the size - you might have to pull it out of the can - it could even fit in the BMI shell with some short jump wires, as you suggested. It would swap electronics for electro-mechanical but as I noted above, "This feels like a lot of electronics and probably overkill". @Erikl indeed you could build a NE555 version of the BMI but you would also need timing capacitors/resistors and a power transistor or a relay to ground the 12V feed from the warning lamp.

 

The wisdom of TLF'ers and op-amps shall conquer all. 😂

Edited May 31, 2019 by ekwan

[march]

@swindon_alan - I have cheked all my spares and rediculously I cannot find one. I know I have a couple but I need them. I will continue looking tomorrow but I will probably need the unit back that I send. Courtesy of the TR7 community here are the contents of the unit - simple eh!. It is just a bimetallic strip that warms up over time and only releases after the current has stopped and the strip has cooled down. Who needs electronics when hot metal will do 🤪.

One good thing - I can now get into the stable with some of the TR parts, tomorrow stable number 2!

[march]

@swindon_alan

Hi - I have found a unit (it's a bit ropy but it should work). I think I have also found an alternative electronic version but I don't know the pin out, I have bought one anyway (only £6.50 inc postage), it's from a Honda Goldwing GL1200 1984-87 which could be a better option and will send it along as well. The Relay is labelled ET-65.

The Honda unit is has 4 pins and the sender appears to have 3 pins so logically one should be a low fuel switch. Feel free to destroy the honda unit if need be as they are cheap enough - and to be honest these may be a good replacement for the Triumph ones as well.

The Triumph one is from the rally car harness so would prefer to have it back, Thanks.

Please message me with your address so I can send them on.

Marc

As a note Harley Davidson do a unit as well but I don't know if it works from a switched sender.  

[swindon_alan]

Smiths BDS100x diagrams:

(Drawing says Lucas, duh! It is a Smiths Industries part).

BMI pin mappings bottom right. Note that the two pairs of terminals can be connected either way round and the male/female combinations ensure that you shouldn't get them wrong. Well at least on a TR7!

I've had a go at the Honda Gold Wing electronic module that Marc sent me but the potting compound appears to be made of reinforced concrete and will take a lot of work with a Dremel to get to the components. When I have a spare afternoon perhaps...

So thanks very much @march, your unmolested relay is back in its Jiffy bag and will be on the way to you tomorrow.

[march]

@swindon_alanI had a little bit more of a look into the Honda units, couldn't find much in the way of wiring diagrams but I did discover that they were used on loads of Honda bikes through the 80's, 90's and 2000's. It may be worth an ask on the motorbike section here to see if any one has an old Honda Haynes Manual loafing their garage (unfortunately my 94 Fireblade does not have a low fuel warning).

[v8GTmac1]

i dealt with this low-fuel relay yesterday. traced the issue from the sender to the light and found there was this doohickey under the hood. Took it out and sure enough keeping the light on. It was the craziest coincidence that I was re-calibrating my fuel gauge needle to then have this happen? I was so confused. 

I opened it, re-soldered everything and working good now. I was about to put the jumper wire but it's now good. 

On 22/05/2016 at 17:18, swindon_alan said:

 

COMPONENTS

CIRCUIT DIAGRAM

 

Jumper wire:

 

 

you did great work here, you mind doing one for the factory ECU?

Edited May 14, 2021 by v8GTmac1

[mike_sekinger]

Hi Michael,

Sadly Alan passed away last year.  He did do an awful lot of great work behind the scenes and is still very much missed amongst us.

Mike S