Wiring oddities, parasitic drain and Tuscan fusebox in cerb
Discussion
Dim dip switching. Why?
Separate Fog light relays. Why?
Separate Sides, Dip and main beam. Why?
Indicator switching unit. Why?
Silver Key. Why?
I mean really, why?
There is ZERO point to any of the above and TVR made it exceptionally complex for no reason at all.
To any that are interested, 4 of the control units in the back of the TVR can be ditched, as can the silver key.
Fitting a Tuscan fusebox will do this, but NOT the ridiculous hash that they made of the idea when the original cerbera fuseboard was made obsolete and they brought out the service bulletin with yet more connections.
Armed with a tuscan fuseboard, some VERY questionable wiring diagrams and a service bulletin, I have successfully implanted the Tuscan fuseboard in the cerbera.
It is not without its problems as probably 80% of the relays in the cerbera are negative switched for ease of wiring, which makes the install less than favourable as you have to make some seriously convoluted changes to the fusebox.
BUT, the outcome is 4 less control units, some beefier wiring and zero chance of a fire as a result of the poor connections, oh and no silver key
As a result of the above modifications, is has reduced the parasitic drain of the Cerb down to a much more manageable 4ma. I believe this to be a result of the dim dim drive unit being permanently live. Will also eliminate the issue of low voltages at the headlights as a result of compound resistances across the loom.
When I officially open the workshop, think I might have to offer the service.
Always makes me wonder what TVR were thinking, I mean, there is a better way of doing so many things!
Separate Fog light relays. Why?
Separate Sides, Dip and main beam. Why?
Indicator switching unit. Why?
Silver Key. Why?
I mean really, why?
There is ZERO point to any of the above and TVR made it exceptionally complex for no reason at all.
To any that are interested, 4 of the control units in the back of the TVR can be ditched, as can the silver key.
Fitting a Tuscan fusebox will do this, but NOT the ridiculous hash that they made of the idea when the original cerbera fuseboard was made obsolete and they brought out the service bulletin with yet more connections.
Armed with a tuscan fuseboard, some VERY questionable wiring diagrams and a service bulletin, I have successfully implanted the Tuscan fuseboard in the cerbera.
It is not without its problems as probably 80% of the relays in the cerbera are negative switched for ease of wiring, which makes the install less than favourable as you have to make some seriously convoluted changes to the fusebox.
BUT, the outcome is 4 less control units, some beefier wiring and zero chance of a fire as a result of the poor connections, oh and no silver key
As a result of the above modifications, is has reduced the parasitic drain of the Cerb down to a much more manageable 4ma. I believe this to be a result of the dim dim drive unit being permanently live. Will also eliminate the issue of low voltages at the headlights as a result of compound resistances across the loom.
When I officially open the workshop, think I might have to offer the service.
Always makes me wonder what TVR were thinking, I mean, there is a better way of doing so many things!
Edited by tofts on Wednesday 17th February 22:11
finished artical, all heatshrunk and ready to go
deciphering the fusebox as there are no wiring diagrams!
mid process
inside the fusebox this is layer 3 of 7!!
Just a little bit of fettling to make it fit in the original hole, then bind the loom up so it looks original. Will post more pics when completed! but it functions as it should now, and far better than the original!
Edited by tofts on Wednesday 17th February 22:48
tofts said:
As a result of the above modifications, is has reduced the parasitic drain of the Cerb down to a much more manageable 4ma. I believe this to be a result of the dim dim drive unit being permanently live. Will also eliminate the issue of low voltages at the headlights as a result of compound resistances across the loom.
When I officially open the workshop, think I might have to offer the service.
Very impressive work that seems it will really make a difference. Wish I had the patience the attempt that myself, as the safety gains sound very worthwhile.When I officially open the workshop, think I might have to offer the service.
The MIL light is driven directly by the ECU, which is driven live by the immobiliser so yes, it does. Its the Ligth green/black wire.
Don;t forget the wiring diagrams are horrendously wrong, I went over every single one and corrected them all at the start of the project, see below for a taster...
So your diagram may show something different, that is actually wrong!
As of now, I think I pretty much know everything about the car with regard to wiring. For days I was dreaming cables!
compared to...
Don;t forget the wiring diagrams are horrendously wrong, I went over every single one and corrected them all at the start of the project, see below for a taster...
So your diagram may show something different, that is actually wrong!
As of now, I think I pretty much know everything about the car with regard to wiring. For days I was dreaming cables!
compared to...
Edited by tofts on Thursday 18th February 08:37
tofts said:
The MIL light is driven directly by the ECU, which is driven live by the immobiliser so yes, it does. Its the Ligth green/black wire.
Don;t forget the wiring diagrams are horrendously wrong, I went over every single one and corrected them all at the start of the project, see below for a taster...
So your diagram may show something different, that is actually wrong!
As of now, I think I pretty much know everything about the car with regard to wiring. For days I was dreaming cables!
compared to...
Legend Don;t forget the wiring diagrams are horrendously wrong, I went over every single one and corrected them all at the start of the project, see below for a taster...
So your diagram may show something different, that is actually wrong!
As of now, I think I pretty much know everything about the car with regard to wiring. For days I was dreaming cables!
compared to...
Edited by tofts on Thursday 18th February 08:37
1998. All years will have similar wiring looms, but later cars have the Tuscan fusebox as standard.
BUT
It is only a replacement for the obsolete Cerb, Griff, and Chim fusebox and does not do away with the ECU's.
Had the R&D department looking in to it a little further, they might have realised that they could save themselves these extra ECU's and thus some money!
I still have a couple of relay spaces left and will try in the coming days to put the wiper control relays inside the fusebox as well, can be done but may not be totally feasible as I will have to run more power feeds, and I don't like just putting in wires unless I can find a space in the rear harness splice to put them in
BUT
It is only a replacement for the obsolete Cerb, Griff, and Chim fusebox and does not do away with the ECU's.
Had the R&D department looking in to it a little further, they might have realised that they could save themselves these extra ECU's and thus some money!
I still have a couple of relay spaces left and will try in the coming days to put the wiper control relays inside the fusebox as well, can be done but may not be totally feasible as I will have to run more power feeds, and I don't like just putting in wires unless I can find a space in the rear harness splice to put them in
Originally started without taking the fuse box apart but soon discovered this was a poor idea. Many of the wires are labelled incorrectly so this is not something that you do with them. I wired it up the way it "should" have worked but found it blew up my steering Column ecu just for kicks.... Thankfully I had the car running off of my bench power supply with a low current limit which minimised the damage. so after a little bit of reverse engineering I managed to fix that problem and carry on. It was at this point (and 3 days in) I decided to cut everything out and start again. But without the diagrams, stripped down the fuse box and worked out all of the pin definitions and started again. Should have done this first as I managed to do the rest of the work in about 2 full days. As it turns out I had missed one of the tuscan fuse box pin locations and shorted the low voltage pull to ground output from the steering ecu directly the +12.
But I do now have a full set of correct diagrams for a cerbera and a pin output diagram for the tuscan fuse box. I will upload them to the website as soon as it is live so all can use!
But I do now have a full set of correct diagrams for a cerbera and a pin output diagram for the tuscan fuse box. I will upload them to the website as soon as it is live so all can use!
tofts said:
As a result of the above modifications, is has reduced the parasitic drain of the Cerb down to a much more manageable 4ma. I believe this to be a result of the dim dim drive unit being permanently live. Will also eliminate the issue of low voltages at the headlights as a result of compound resistances across the loom.
When I officially open the workshop, think I might have to offer the service.
Out of interest, what was the original current drain with your cerb and was that with or without the alarm/immobiliser being armed?When I officially open the workshop, think I might have to offer the service.
Do you know what, I never measured it. I just know it was high as it would drain a battery fairly quickly, sometimes in a matter of days. On inspection of all diagrams, there are quite a lot of systems that could leak current as they would need to be live with the car "off" , and removing them has helped greatly
Next time I get a Cerb through the workshop I will endeavour to measure it. Have a tuscan at the moment and will measure that just out of curiosity.
Next time I get a Cerb through the workshop I will endeavour to measure it. Have a tuscan at the moment and will measure that just out of curiosity.
Most radios pull 3-4, 4 or so for the siren, then the clock. My cerb has the later fusebox and those are the figures I get. Other late cerbs I have worked on are around the same so these figures seem to stack up...
To be honest many of the current draw issues I've fixed on clients ' cerbs over the years have been caused by bodged aftermarket additions or other issues rarely caused by the fuseboard. Nice work, though...
To be honest many of the current draw issues I've fixed on clients ' cerbs over the years have been caused by bodged aftermarket additions or other issues rarely caused by the fuseboard. Nice work, though...
Personally, I think the dim dip has a lot to answer for, only takes a leaky filter diode or broken down power mosfet to give you even more drain. When I have a spare afternoon, I was going to take a more detailed look at it. Its a hunch, but after seeing some of tracks inside the switching units, it makes me cringe at the current draw and how small they are. poorly designed.
Also, inside the relay units most of the relays have a fly back diode, which are not necessary as when you start looking, all of the Logic level is driven by Darlington drivers that have integrated clamping diodes to drive inductive loads. Its all possible leakage paths, and I was determined to eliminate them!
Also, inside the relay units most of the relays have a fly back diode, which are not necessary as when you start looking, all of the Logic level is driven by Darlington drivers that have integrated clamping diodes to drive inductive loads. Its all possible leakage paths, and I was determined to eliminate them!
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