Page last updated 17 October, 2011

Technical Questions - Electrics
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Date asked

Question Answer

9th October 2011

By Duane

1974 2500m tach is working intermittently ,starts working after the car is moving. Works better when warm, but dies when idling at times. Never stops when rpms are higher. Where do I start?



Response by Duane

The first thing I did was check, clean & tighten the connection at the coil. Started the car & it worked right away. Thanks


I would first suggest you check all connections from the coil negative terminal right back to the back of the tacho. Any poor connection in this wire could cause the intermittant problem you are experiencing. Using a multimeter to check for continuity in the wire is the first step - disconnect the wire from the coil negative terminal and the back of the tacho and check there is no resistance in the wire. Anything above 1 ohm will mean the wire has a resistance somewhere indicating a poor connection. If this test shows all is well in the wiring, and there is no misfire at idle speeds (and whenever the tacho is not operating), then it will most probably be your tacho has an internal fault. This is quite common and someone like Speedy Cables (see my links page) can carry out a repair for you.

17th June 2008

By Simon McGovern

1979 Taimar.
Are the standard sealed beam headlamps powered by relay, or direct from the switch. We want to exchange for replacement halogen units & need to no wether to add extra relays to handle power?
There's no relay on the original wiring I'm aware of - please see my wiring diagram which I prepared from an old diagram sent to me by a member. You will see the switch is the main/dipped beam stalk switch rather than a relay. See wiring diagram on this website. Just to add that aftermarket looms (like the autosparks loom) can include the relay. If your wires aren't simply black with coloured collars then you may have an aftermarket loom.

21st April 2008

By Andy

Need a new batt for my Taimar Turbo, any ideas of best make and models. Generally with batteries, the bigger the better in terms of cranking power, but smaller batteries are ok for the older TVRs if used regularly only in the warmer months. Battery codes vary but the standard code 015 is the small one and works well in the 3000M so will be fine for the Taimar. Pop down to your local Halfords store and check the terminal configuration matches your wiring. This battery is the one that used to be the heavy duty type used on the old Mini. If you need more power and run the car regularly in the winter (i.e. use the radio a lot when the engine isn't running) then go for an 063 battery which is larger and better suited. Again check the terminal layout before buying.

As for makes of battery, they are all pretty much the same in the retail market, but try your local motor factors as they can usually beat high street prices.

15th January 2008

By Eoin Mc Cabe

I'm mid way to putting back together my own 3000M. can iask you were you got the electrical water tight connector block? i cant find one as neat as yours it'd be a great help. thank you.
I bought the connector from Vehicle Wiring Products way back in 1999. The part was in their catalogue listed as a Weatherprrof Connector, and the part numbers were: WP3, WP5, WP7, WP9 respectively for 3, 5, 7 & 9 way connectors. Not sure if they still do them as they don't seem to appear on their website - may be worth calling them to find out - tel 0115 930 5454 (they don't appear top have an email address either!).
Website address is

30th May 2007

By Fam Christians

I have a 3000S and i wounder were does the rear lamps comes from? They are from the Aston Martin Vantage from the 70's, Reliant Scimitar GTE also had them, plus a Lotus model (either Elite or Eclat but not 100% certain on this) - again 1970's models.

23rd October 2006

By Paul E. Ruisinger

I was wondering if you know who makes the heater blower assy. I have a 76 3000M I am looking at various MG units at the moment as they seem to be very similar. Will let you know on cost if you are interested as I am trying to stock them, but waiting for a reply from the supplier.

Update on 11th June 2007 - Supplier never replied. Looking into replacement motors with higher output.

11th May 2006

By Jeff Roth

How difficult was it to remove the original wiring loom and later thread
back a replacement wiring loom, like from Autosparks? The wiring on my
2500M has suffered from 30 years of improvisation by the previous owners.
I'm trying to decide whether to sort out their design and routing choices or
scrap theirs' and buy the harness, recently quoted to cost 213.75 Pounds.
The loom removal requires dashboard and centre console removal, carpet lifting to get to the front to rear, also all the engine wiring which is a bit tricky so would advise removing the bonnet! Starter motor wiring is the most difficult to get to, along with wires for bonnet and electric radiator fan if fitted.

I have used the autosparks harness which works well, but as it's a general M series harness expect to find a few wires that you won't need, and you will also need to fit your own fuseboxes (unless they have modified the loom since I bought it in 1999). Lay it all out first and label each wire to make fitting on the car much faster...I seem to remember ignition lock and fuse wiring was the most difficult to sort out, but the colours help as they are to BS wiring codes.

7th February 2006

By Christian Proud-Diaz

I had a trouble with my TVR 3000s on the way back home, by night : no lights...

Fuse and light switch looks ok, reverse lights are working, stop lights and indicators too.

But I have no tail lights, no front lights (main beam, high beam works if use the swith on the steering column) and the dials are working, but not their lamps.

Any advice? What could I check else?


Follow up by Christian on 10th Feb 2006

Thanks, problem fixed. It was the switch! I will change all of them for à set of Lucas toggle switches : much better look to my opinion!

Ok, first things to always check are voltage present. Pull the main lamp switch out and check for 12V feeding the switch. It receives a feed from the fed to the ignition switch which is in turn fed by fuse number 7. This assumes you have the original wiring. The problem shouldn't be an earth as each lamp has its own earth. If there is no voltage going to the switch then you will have to trace the feed wire going back to the connection with the feed to the ignition. Sometimes this connector (bullet type) can get some corrosion on it or work loose - a simple clean up should fix it. Use a voltmeter and simply put the black probe on an earth, then check for 12V at place down the wire until you find a voltage.

29th January 2006

By John

I have a few issues that you or other users may be able to help with! My motor is a 78 Taimar.

1. The rheostat switch for the dash lights - do you know where it may be located, behind the dash for example, and what it may look like? I guess, looking at your wiring diagram, this may the offending item stopping all my dial lights from working. I have had the dash panel off and all dials disconnected. Not easy!

2. If both my reverse lights do not operate, apart from checking the bulbs and the gearbox switch, what would you check next please that could be a common issue?

3. At the front of my engine bay, mounted on the inside of the bonnet on the nearside edge of the grille, is a hairdryer shaped, electrical powered thing with a vent pipe that, although not connected, seems to connect to the front of the airbox on the nearside wheelarch. I cant see this on the wiring diagram. I guess its just an interior cold air blower?

I am new to TVR electrics!

In answer to your questions (all assume original TVR wiring - black with colour coded collars).

1. The rheostat is on the back of the dimmer switch knob. If your car hasn't got one then maybe someone removed it, or perhaps the car never had one fitted (TVR were very individual with their interiors)! What you'll need to do is check that the bulbs all have good earths, and 12V feeds with the lamps on. If no earth then you'll need to check the method of each bulb holders' earth connection at both ends. It could be the main earth for the dashboard, but I suspect not if other items are working. use a multimeter set to Ohms to check full continuity of earths (i.e. ) 0 Ohms or just above. If this is ok, check for 12V at one bulb holder + wire. If no 12V, follow the wire back to the dimmer rheostat or further back to its connection to the main light switch. Somewhere along this wire you should find a fault. It won't be a bulb as only the blown one will be out. If less than 12V you will have a short circuit somewhere. If 0V then an open circuit (broken wire or component).

2. Apart from the bulbs & fuse, check the earths to the rear lamps, also the bulb holders are making good connections to the bulbs. Check brake lamps illuminate as these should be powered by the same 12V feed. Then make sure the reverse lamp wires are connected correctly to the bulb holders. If all ok, check for 12V on feed wire to bulb at rear lamps. If no 12V then follow wire back to (nearside or l/h side I think) connections in A post in front of door. Check the wire here for 12V. If none then follow back to reverse lamp switch (wire goes in dash, then down under centre console to gearbox). If no 12V at reverse lamp on feed side (not the wire to lamps side) then check the wire from here to the fusebox (going via brake lamp switch assuming original wiring). Remember less than 12V but above 0.1V approx. means wire is shorting out on another wire or has broken down due to a resistance (e.g. corrosion within wire or poor connections). This will mean a pretty detailed investigation is required.

3. You are right, on the Taimar the Heater motor was located right at the front of the car for some reason - probably to reduce interior noise and also provide less of an obstacle for the passengers legs! There should be a long convoluted hose joining this up to the nearside (l/h) scuttle panel/inner wing area, but many are discarded as they get in the way of maintenance.

30th October 2005

By Thomas

Can you tell me what car the wiper-mechanism comes from? The Wiper motor should be from the Triumph Spitfire or TR4-TR6.

1st August 2005

By Stefan Gurszky

As my gaskets/seals of my flasher, sidelamps, reak lamp cluster,... are worn (shrunk, lost elastics) and those items are hard to get, I plan to do them myself. Using the old one as guide, I'll scan them and brush the images up with some software. Do you know which material I should use for those seals? Will closed cell neopren do the job and last for some years or are better materials around? Neoprene is the best gasket material when it comes to weather/UV resistance - in my past experience I used it in the glazing industry. Closed cell neoprene would be pretty good I'm sure - and without doubt a lot better than the original foam gaskets.

21st July 2005

By Stefan Gurszky

My car has already the quick bonnet release modification, using the same electric connector as you suggested. So far,I have found no way to disconnect that thing - I tried to twist, push, press,... but I didn't wanted to use too much force as I don't want to break it. I'm sure it is quite simple, but maybe I'm too stupid for that part! And idea?


Follow up on 22nd July 2005:

Thanks for your quick reply - connector separated without destruction!

The bonnet connector should simply pull apart, but the rubber sleeve that makes the connection of the two halves waterproof has a tight grip on the connectors. You could try to peel this back slightly first before you remove it.

25th April 2005

By Mike Garcia

Re: 1979 Tamair 3.0 liter V6

I recently experineced noticable clicking noise . I adjusted the Rocker arms clearances and a bit better. The noise really occurred after the engine was hot & running hard 3,500 rpm 80 mph for 20 minutes. I heard a gear like noise or somthing snapped after down shifting. Cant discover the problem. Also noticed the red ligt comes on, howver I feel the liight is due to a bad voltage regulator. Does the red light also monitor the enginie, and not just the ignition?

Not sure if all the M series cars had just an ignition light, but that's normally lack of charging (more noticeable on idle). Do you have a voltmeter or ammeter gauge? If not put a multimeter on the battery terminals with the engine running andmake sure you're getting approx 14.4V - then it's charging ok.

The clicking noise is a bit more worrying. Is the engine still running ok? My guess is that you have burnt out a valve (which is quite common) or possibly head gasket. Check the compression of each cylinder & check the website Engine section for data. Make sure the pushrods are not bent. Have a look at the distributor cap as poor fitting types can slip allowing the rotor arm to chop away at a contact or two, making a noise and causing poor running.

If not the above, perhaps the camshaft fibre gear teeth may have snapped (unless you have a steel gear now)? I would certainly take the front cover off to have a look if valves/head gasket seem ok after a compression test.

Have you checked the oil pump drive isn't worn? See oil pump & sump in engine section on website. But, your oil pressure gauge will tell you if that's slipping - I'm just thinking that if you do have an oil pressure warning lamp fitted then maybe the drive spindle is worn out (very common on these engines).

Lastly perhaps a gearbox problem, but that should be easy to detect if you have trouble changing gear.

28th August 2004

By Paul

On the original Lucas alternator how many wires went to it. and colors.(not spelled wrong) (Essex V6 engine.)

Now here is my problem, a prior owner put in a Hatachi alternator. the 2 large brown wires went to one post marked BAT and the small ignition light wire is attached with a spade connection to where the Hatachi would take a 2 wire plug in connection.

When I have the car on and driving the ammeter will always read on the minus side whenever I turn on anything (lights fan, or just step on the brakes) and reads at "0" never moving to the plus side at all. A volt meter across the battery terminals when the car is running will show 14.5 - 15.00 volts so I am charging. Could there be a hookup issues with this alternator?
any thoughts?
Have you tried connecting the small wire to the other terminal? Just a thought. Also, do you have an ignition light connected? If so does it come on until the engine is running. Usually the fat battery wires go to the BAT or large terminal as you say, so it is connected properly and should give a charge so that's ok. Also, is the ammeter wired up the right way round?

1st July 2004

by Steve & Sam Twin

Fuse problems solved!

Just something to add to the tech. section if you think it's of interest.

My son has a 1980 Taimar. We went to Bromley Pageant last weekend. On leaving the parking area (bumpy field) the car stopped. I traced the problem to a blown 50 amp fuse on the ignition circuit. This was changed - obviously it blew again. Couldn't see anything wrong but eventually got things going by removing the fuse that protected the indicators/stoplights/warning lights/instruments/wipers etc and putting into the ignition position in the fuse box. Drove home without any indicators/stop lights!!

Once home managed to isolated the short circuit down to a couple of things by removing the contacts on the back of the fuse box one at a time. Got it down to instruments/indicators/warning lights etc.

The problem turned out to be the instrument retaining clamp at the top of the rear of the tacho. The knurled nut had worked loose allowing the bracket to swing down,shorting across the contacts on the rear of the vertical row of warning lights.

Remedy - took off the clamp, wrapped it in insulating tape and replaced it. Replaced the fuse - problem solved.

Beware bumpy car parks at shows!

Steve & Sam Twin

4th June 2004

by Steve Jones

I am restoring a 1973 2500M ser# 2733 I am trying to find front side marker lights. They are left and right handed, I would like to know what they are off? Can you help? I have enclosed a picture of one that I took at a British Car Meet. Also two pictures of my car to date.

Here is a copy of an email I received recently about this:

No idea what the marker lights were originally fitted to (if anything) but I think they are a general export fitment for a lot of UK cars that went to the USA. You can usually pick new ones up from autojumbles for a few quid.

Hope that helps you, but only for what they fitted....that is - not sure! As for finding some, they are pretty rare I think - want to try a wanted ad. on the website? It's free and normally you'll find someone has the part sitting in their shed or something....let me know!

26th February 2004

by Tony Kilbee
How do I check the charging circuit? The ammeter reads zero and I know that I'm running on battery only?
A faulty ammeter can prevent the battery from charging as the wiring from the alternator runs through the meter to the battery. Get a voltmeter and test the battery voltage with engine running at approx 2000rpm - reading should be approx 14-14.4V
If not and your ammeter isn't working, first see if the feed to the ammeter is +12V, if so, gauge is faulty. If not then it's possible the alternator regulator is faulty or brushes are worn.
29th June 2003

by Kevin Farrington
l have recently purchased a tvr,been in garage for 10 years, engine runs and headlights work, but none of the other lights work including radio, heater. Is it the earths, and where do l find them? Also engine overheats and fan blows cold. The main earth points for the wiring harness are found on the top chassis rails next to the engine (1 on each side). These do have the tendency to corrode sometime, and the wiring or connectors may need checking at this point. Also check the bullet connectors to all the components - an equally likely place to find the fault. These usually corrode up after long term storage and either a good clean up or replacement may be the fastest way to solve these problems. Bullet connectors also reside on the back of the front indicator/sidelamp units and are the first to corrode due to their location.
Other earth points to the chassis are located at the back of the car just in front of the fuel tank, and an earth wire runs up to the fuel tank from here so that it becomes an earthing point for the rear wiring harness (there should be 2 studs with spade terminals on for this purpose).
Regarding the overheating & fan blowing cold - do you mean the heater fan? Just that you said fan wasn't working! If the heater isn't getting hot (but the engine is), a common fault is the heater control valve sticking which prevents correct circulation. Best thing to do as a short term fix (unless you have a spare valve handy) is pipe the heater matrix into the water circuit without using the valve - it should now run hot. If still not working, the matrix could be clogged up and needs flushing out. The overheating may be because the electric fan isn't working, or the radiator fans or core is blocked. Listen out for the fan once up to full temperature while stationary, if it works then look to see if the radiator fins are blocked with dead insects/foliage, if not then remove the radiator and see if a flush out with a hose pipe removes any residue. If the fan's not working then remove the two wires attached to the otter switch (radiator fan switch) and with the ignition on, touch the connectors together (or use a spare piece of wire to join them). The fan should now work. If not, check a 12v is reaching the otter switch feed wire, and if so then the fan could be faulty. Try to spin it by hand (this will check if it's seized). if not seized, then you could remove the fan and open it up to check if the motor brushes are worn out, or simply replace it.
14th May 2003

by Steve Bourne
I have a 1977 3000M.
When the fuel tank is empty, the gauge reads a quarter full. Is this
Is there any scope to re-calibrate the sender unit so the gauge reads

This 1/4 full reading is common. The sender unit is from a production car (not sure which but probably Triumph TR6) but fits to the TVR made tank. The car on my website had a new sender 2 months ago, and I've had to shorten the float wire & bend it to give a better reading. It now reads empty when it's nearly empty - I basically did it by trial and error with the tank very low. I would suggest trying to modify the sender rather than buying a new one, unless you know the sender's faulty.

The cause is that the float wire is too long, and pointing too far down. This means it bottoms out on the tank, not on its stop tab on the top of the sender. Just bending the standard length float wire up a bit works, but then the gauge never goes above 3/4 full - so the problem is moved to the other end!

To shorten it either use some pliers to make a couple of 90º zig zag bends which will allow it to be shortened without cutting off any wire or disturbing the curved shape which holds the float, or remove the float and trim off a bit of wire, making a new curve for the float (more time consuming and more chance of cutting off too much).

See below for idea of what is required.