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RELAY..Low fuel? BDS 1004 Giving grief

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bonnietiler
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RELAY..Low fuel? BDS 1004 Giving grief

Postby bonnietiler » 04 Apr 2019 15:04

I have this relay under the steering wheel just taped in there.
It has started effecting the Indicators..strange I know.
It is a Smiths Relay/switch Stamped BDS 1004
Connections include an earth
double green
Green/Brown
Brown/Green.
I cant find any details of the rascal
Any help much appreciated

saabfast
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Re: RELAY..Low fuel? BDS 1004 Giving grief

Postby saabfast » 04 Apr 2019 18:08

This listing on US ebay suggests it is the low fuel delay. Certainly looks like it (normally fitted to the top of the instrument cluster under the cowling).
https://www.ebay.com/itm/NOS-Smiths-Low ... 3192370154
On the wiring diagram it seems to take a feed from the hazard switch so that my be why it is affecting the indicators if dodgy.
Rimmers list it as NLA. Probably best to try the usual suspects (Robsport, S&S etc) for a s/h replacement.
Alan
Saab 9-5 2.3t Vector Auto Estate Stage 1
Saab 9-3 2.0 SE Turbo Convertible
'81 TR7 DHC
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oliviertr7
Wedgling
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Re: RELAY..Low fuel? BDS 1004 Giving grief

Postby oliviertr7 » 04 Apr 2019 19:54

Image

black - double green - green red and green orange
Image

saabfast
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Re: RELAY..Low fuel? BDS 1004 Giving grief

Postby saabfast » 04 Apr 2019 21:08

Looks a slight variation on the wiring diagram I have. That does not show the doubled up connections. It shows:
Green - G -from Hazard switch
Green/orange - GO - to tank unit
Light Green/Red - LGR - from the low fuel warning light
Black - B - ground

By the looks of it the when the low level contact in the tank unit makes to ground the current through a resistance in the delay unit heats it. The warning light 'switch' in the delay unit must be bimetal type contacts. The heat makes the contact from the warning light to ground. The power to the warning light is from the instrument panel printed circuit.

The doubled up green must be a power supply from the hazard unit to something else and the ground has been linked to something else.

My interpretation but hope this helps.
Alan
Saab 9-5 2.3t Vector Auto Estate Stage 1
Saab 9-3 2.0 SE Turbo Convertible
'81 TR7 DHC
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saabfast
TRiffic
Posts: 1757
Joined: 03 Feb 2006 08:17
Location: Royal Tunbridge Wells

Re: RELAY..Low fuel? BDS 1004 Giving grief

Postby saabfast » 04 Apr 2019 21:17

Actually, looking further at the diagram there are connections on the green cable feeding the likes of the wash/wipe switch and stop light switch. It seems to be a common power feed so the double up must be to one of them.

Try pulling the green connection from the delay unit and see if that solves your problems as that will disconnect the unit from the power feed.
Alan
Saab 9-5 2.3t Vector Auto Estate Stage 1
Saab 9-3 2.0 SE Turbo Convertible
'81 TR7 DHC
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dursleyman
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Re: RELAY..Low fuel? BDS 1004 Giving grief

Postby dursleyman » 05 Apr 2019 00:01

I pinched this picture from Odd Hedberg showing the internals of the low fuel warning unit for what its worth

Image
Russ

1981 TR7 Sprint DHC
Dursley
UK

http://tr7russ.blogspot.co.uk/

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saabfast
TRiffic
Posts: 1757
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Location: Royal Tunbridge Wells

Re: RELAY..Low fuel? BDS 1004 Giving grief

Postby saabfast » 05 Apr 2019 17:12

Basically shows what I described, the heating element on the bimetal strip contact. Sloshing the fuel in cornering will only give momentary power to the unit, not long enough to heat the strip to make contact so stopping the light from flashing. If the level stays low for long enough it will allow the strip to heat enough to bend and make contact, illuminating the low fuel light.
Alan
Saab 9-5 2.3t Vector Auto Estate Stage 1
Saab 9-3 2.0 SE Turbo Convertible
'81 TR7 DHC
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