S3 voltmeter problems
Discussion
Hello from a new S3 owner.
I have just bought a 1991 S3c and have a problem with the voltmeter.
When a load is placed on the battery such as the headlights and interior fan or indicators the voltmeter reading drops significantly.
When I use the indicators, the voltmeter dips from the 13v midway position in time with the indicators and the handbrake warning light on the dash also dims in time with the indicators. On the road whilst driving, the speedo reading increases when the indicators flash.
I've read about the alternator not charging until over approx 2200 revs and the charge light goes off.
I've tested the battery and alternator using a "proper" voltmeter and at a steady 2500 revs, there is 13.7 volts at the back of the alternator and across the battery whether there is a load applied or not.
The other thing I've noticed is that if I turn the hazard lights on, the voltmeter doesn't move from the 13v position and the dash warning lights stay bright and do NOT pulse in time with the flashing.
Any ideas what's going on ?
Thanks
David
PS I would add that I've already cleaned up the 3 chassis earthing points under the bonnet and used stainless steel washers and nylocks in place of the rusty mild steel items and then given the earths are liberal spray with waxoyl to keep moisture out.
I have just bought a 1991 S3c and have a problem with the voltmeter.
When a load is placed on the battery such as the headlights and interior fan or indicators the voltmeter reading drops significantly.
When I use the indicators, the voltmeter dips from the 13v midway position in time with the indicators and the handbrake warning light on the dash also dims in time with the indicators. On the road whilst driving, the speedo reading increases when the indicators flash.
I've read about the alternator not charging until over approx 2200 revs and the charge light goes off.
I've tested the battery and alternator using a "proper" voltmeter and at a steady 2500 revs, there is 13.7 volts at the back of the alternator and across the battery whether there is a load applied or not.
The other thing I've noticed is that if I turn the hazard lights on, the voltmeter doesn't move from the 13v position and the dash warning lights stay bright and do NOT pulse in time with the flashing.
Any ideas what's going on ?
Thanks
David
PS I would add that I've already cleaned up the 3 chassis earthing points under the bonnet and used stainless steel washers and nylocks in place of the rusty mild steel items and then given the earths are liberal spray with waxoyl to keep moisture out.
Edited by The Horse on Monday 18th September 09:05
The problem is caused by a voltage drop somewhere along the ignition circuit and is often caused by bad connections at the fuse-box
Below is a link to an idea I had in the recent past that will overcome your problem
https://www.pistonheads.com/gassing/topic.asp?h=0&...
Below is a link to an idea I had in the recent past that will overcome your problem
https://www.pistonheads.com/gassing/topic.asp?h=0&...
As phillpot says - they all do that
so the best thing to do is rewire it
just pull the existing + and - leads off and tape up or cut off so they cannot cause a problem later
Then run a new lead to a good earth and the other either to the battery, starter connection or alternator output (or similar) that way you know it is reading the alternator or battery voltage.
so the best thing to do is rewire it
just pull the existing + and - leads off and tape up or cut off so they cannot cause a problem later
Then run a new lead to a good earth and the other either to the battery, starter connection or alternator output (or similar) that way you know it is reading the alternator or battery voltage.
magpies said:
As phillpot says - they all do that
so the best thing to do is rewire it
just pull the existing + and - leads off and tape up or cut off so they cannot cause a problem later
Then run a new lead to a good earth and the other either to the battery, starter connection or alternator output (or similar) that way you know it is reading the alternator or battery voltage.
Oh dearso the best thing to do is rewire it
just pull the existing + and - leads off and tape up or cut off so they cannot cause a problem later
Then run a new lead to a good earth and the other either to the battery, starter connection or alternator output (or similar) that way you know it is reading the alternator or battery voltage.
Penelope Stopit said:
magpies said:
As phillpot says - they all do that
so the best thing to do is rewire it
just pull the existing + and - leads off and tape up or cut off so they cannot cause a problem later
Then run a new lead to a good earth and the other either to the battery, starter connection or alternator output (or similar) that way you know it is reading the alternator or battery voltage.
Oh dearso the best thing to do is rewire it
just pull the existing + and - leads off and tape up or cut off so they cannot cause a problem later
Then run a new lead to a good earth and the other either to the battery, starter connection or alternator output (or similar) that way you know it is reading the alternator or battery voltage.
Mick, if only it was that simple. 
I think Penelope would insist that you should include at least three relays, a couple of diodes to prevent back emf, and a choke or two to prevent arcing at the yellow connector.
Oh, and make sure you use only the very best quality scotchloks.
The issue is the marginal wiring loom quality / sizing and 'odd' configuration choosen by TVR.
As a starting point it is worthwhile going round the car checking the earths points and cleaning if required.
However, as stated, tadts.
Swapping the indicator bulbs to LED and fitting an appropriate / matching indicator relay will mitigate this particular issue.
If you understand [basic] car electrics then you can run through and test circuits. You may find that previous owners may have undertaken temporary repairs and then not returned to fixed properly. The wires have a torid time in the engine bay and suffer heat damage more than most other cars. I found over 20 faults in Wendy's engine bay during the light refurb I did recently. Spending some time fixing these things go a LONG way in providing reliability.
As a starting point it is worthwhile going round the car checking the earths points and cleaning if required.
However, as stated, tadts.
Swapping the indicator bulbs to LED and fitting an appropriate / matching indicator relay will mitigate this particular issue.
If you understand [basic] car electrics then you can run through and test circuits. You may find that previous owners may have undertaken temporary repairs and then not returned to fixed properly. The wires have a torid time in the engine bay and suffer heat damage more than most other cars. I found over 20 faults in Wendy's engine bay during the light refurb I did recently. Spending some time fixing these things go a LONG way in providing reliability.
The biggest problem with these niggling faults is making a decision to attempt a fix or leave well alone, sometimes attempting a fix will create more faults, sometimes leaving well alone will result in a fire sometime in the not too distant future. This alone is proof that life really is a b
h
It's easy for me to give advice and suggest these fixes as I have no problems with designing and building a complete electrical system for any vehicle, I understand how daunting it can be for those with no or little electrical knowledge and do appreciate that there are very few skilled people that can undertake these jobs and do them to a high standard
This below fix is a very simple method that someone with little knowledge can undertake to get true battery voltage showing on the voltmeter although obviously it doesn't cure the fault. If the fault is factory built then this fix is a definite goer
hIt's easy for me to give advice and suggest these fixes as I have no problems with designing and building a complete electrical system for any vehicle, I understand how daunting it can be for those with no or little electrical knowledge and do appreciate that there are very few skilled people that can undertake these jobs and do them to a high standard
This below fix is a very simple method that someone with little knowledge can undertake to get true battery voltage showing on the voltmeter although obviously it doesn't cure the fault. If the fault is factory built then this fix is a definite goer
Edited by Penelope Stopit on Monday 18th September 12:38
Thanks "Penelope"
Is there a "best place" to fit this relay ?
I've currently taken the centre console out and the glove box to tidy up a previous owner's wiring to the stereo and led interior lights and to try and fix the non-working electric mirrors.
I've also found that the left (nearside) of the fibreglass dash assembly doesn't seem to be fixed to anything. Any idea where / how the dash should be fixed to the body-tub ?
The pipes to the air-vents are also just loose ......
Thanks
David
Is there a "best place" to fit this relay ?
I've currently taken the centre console out and the glove box to tidy up a previous owner's wiring to the stereo and led interior lights and to try and fix the non-working electric mirrors.
I've also found that the left (nearside) of the fibreglass dash assembly doesn't seem to be fixed to anything. Any idea where / how the dash should be fixed to the body-tub ?
The pipes to the air-vents are also just loose ......
Thanks
David
The Horse said:
Thanks "Penelope"
Is there a "best place" to fit this relay ?
I've currently taken the centre console out and the glove box to tidy up a previous owner's wiring to the stereo and led interior lights and to try and fix the non-working electric mirrors.
I've also found that the left (nearside) of the fibreglass dash assembly doesn't seem to be fixed to anything. Any idea where / how the dash should be fixed to the body-tub ?
The pipes to the air-vents are also just loose ......
Thanks
David
You can fit the relay anywhere, the best place is somewhere that is easily accessible should it go faulty and need replacing in the future, the relay will be carrying very little current so it will not overheat, you would be wise to fit a 5 AMP in-line safety fuse at the battery positive for terminal 30 input.Is there a "best place" to fit this relay ?
I've currently taken the centre console out and the glove box to tidy up a previous owner's wiring to the stereo and led interior lights and to try and fix the non-working electric mirrors.
I've also found that the left (nearside) of the fibreglass dash assembly doesn't seem to be fixed to anything. Any idea where / how the dash should be fixed to the body-tub ?
The pipes to the air-vents are also just loose ......
Thanks
David
In using the same method as above you can modify all the ignition controlled circuits by using suitably rated relays with fuses to power those circuits and in doing so all volt drops in those circuits are done away with as long as the correct current rated cable is used (perhaps a job for the future), I can draw you a diagram if you need one
Poster zombeh is the man with much knowledge who will help you with the other problems you mention above
Edited by Penelope Stopit on Monday 18th September 13:41
There are four threaded inserts in the dash (two above the glovebox, two above the steering column) that drop into corresponding slots in the body in the screen demister vent bit, screws go up from underneath into those to hold the top edge of the dash in place. You may well find some of them are inaccessible due to sticking alarm/immobiliser in the way or the inserts having come out of the dash.
The bottom edge of the dash is secured to the side of the tub with a bracket each side.
There are some very helpful photos here https://www.pistonheads.com/gassing/topic.asp?h=0&...
The bottom edge of the dash is secured to the side of the tub with a bracket each side.
There are some very helpful photos here https://www.pistonheads.com/gassing/topic.asp?h=0&...
Penelope Stopit said:
phillpot said:
Penelope Stopit said:
Oh dear
Yeah! Penny's back 
I think Mick's "cure" is a little too simple, Voltmeter will register constantly, time for one of Penny's relays
DamianS3 said:
Penny it shouldn't bother me but when replying to folks I do feel you should start with..
"I don't own or have ever owned a TVR but..."
So ther are no misunderstandings.
Lols just my thoughts
Damian S3
If I wasn't wiser I could have thought this was a personal attack without good reason to do so"I don't own or have ever owned a TVR but..."
So ther are no misunderstandings.
Lols just my thoughts
Damian S3
Thanks for your humour
v8s4me said:
mk1fan said:
............ You may find that previous owners may have undertaken temporary repairs and then not returned to fixed properly. ...
May have? 
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