TR4 Electrical Failure

[Brian Sculpher]

Can anyone assist with an electrical issue with a TR4

Whilst driving today my fuel+temp gauge failed to register, inclusive of brake lights and indicators, although hazards continued to function.

The voltage stabilizer was replaced (item 27 TR4 wiring diagram) brake and direction indicators then operated again. However fuel/temp gauge would not function. I find it odd the heater blower functions correctly item 28/29 which in turn links via the voltage stabilizer item 27.

Is there anyone else who has had a similar experience and can advise what else I could try?

Thank you for your interest in my issue.

Brian S (Plymouth)

[Guest]

Could it be an earth issue ?? Fuel & temp gauges tend to share the same earth.

I take it one day they worked and the next time they did not with there being no signs of imminent failure ??

Regards.

Richard. 

[Brian Sculpher]

Hi Richard yes correct worked continually since renewing wiring harness earlier this year.

i was wondering if the hazard warning lights may be a link to the issue as the carpet in the passenger footwell had moved maybe there is a link fault occurring, perhaps I’m clutching at straws.

What do you think?

Best Brian

[Pete Lewis]

The aux etc should be off the  ign controlled  feed to  the  stabiliser  not from the  stabilised output  that only feeds the two gauges

Cant see any relation between stabiliser and lighting   very seperate circuits, is the fuse box the common place to look.?

Pete

[Guest]

Hello Brian,

I agree with Pete on the lights wiring and stabiliser.

Currently my money is on elec-trickery !!

The fact that neither of the 2x gauges are working indicates a complete lack of electric be it supply or earth - I would be tempted to earth both gauges by a separate wire to a sound earth and see if there is a result.

Secondly, if the above achieves nothing then a multi meter for continuity on the gauges individual supply needs to be checked; along with the physical wire connections check.

The other suspicion has to be the voltage stabiliser (VS) - did you go for the traditional bi-metallic unit (OEM) or the electronic version that you can now purchase ?? Perhaps substitution may prove useful to determine if the current fitted unit is working properly.

Finally and apologies in advance, have you connected the VS correctly and is that unit earthed properly ??

Regards.

Richard.

 

 

[Brian Sculpher]

Hi Richard/Pete,

Believe your on to something with the voltage regulator (VS) as I believe when I ordered the wiring loom earlier this year I included a VS.

As the suppler didn’t differentiate between positive and negative earth, the replacement I installed could well have been positive earth in error.

What do you think, as these connections left no chance for error.

Best Brian

[Guest]

Hello Brian,

For the sake of a tenner or so, I'd go for a new VS - try the electronic version, they are excellent. I've fitted 2x on separate classics and no issues; I do think you need to eliminate that line of enquiry before proceeding.

I would certainly try my suggestions, first, with regard to earthing independently and also the continuity checks before splashing out.

Regards.

Richard.

[Brian Sculpher]

Thanks Richard I will let you know how I get on with your suggestions.

Best Brian

[Guest]

Good luck Brian,

It's a topic that will be of interest to all classic vehicle owners, as the VS is often a point of conversation along with those 2x gauges - not just on this Forum.

Regards.

Richard.

[Pete Lewis]

i dont see the orig    thermo bimetal  mechical stabiliser is polarity conscious  the output/ input lucars are male female so cant get mixed ???   

the stab must have a good earth and is marked top as its not an acrobat

electronics will be polarity aware and guess fail if reversed .

Pete

[Brian Sculpher]

Pete/Richard,

Just to say thank you. The negative earth VS has solved my problems temp/fuel gauges now all working.

As you indicated earlier it’s a potential problem for all owners of classics to ensure they obtain they correct polarity of parts.

Best regards Brian

 

 

[Guest]

Hello Brian,

That is excellent news and thanks for the update - I am glad a solution was forthcoming.

I will be very interested to hear how differently those 2x gauges work compared with the original (working !!) set-up in due course. I expect no difference, but always curious to know.

Well done and no excurse for running out of fuel !!

Best wishes.

Richard.

 

[Brian Sculpher]

Hello Richard,

Thanks interesting, your additional enquiry about the gauges working post VS install.

Fuel gauge working correctly however temp gauge electric fan now operates when gauge first reaches start of normal band. Normally the fan would operate when leaving the normal band region, somewhat worrying if the electric fan failed to operate. Some month or so ago I changed the temperature sender in order to engage at a lower temperature, all was working correctly until vs changed.

Am now somewhat confused as to whats going wrong as I did make sure the wire connectors on the vs were installed on the correct terminals.

I would be interested if you have come across this issue before?

Best Brian 

 

 

 

[Pete Lewis]

is the VS linked to the fan drive  cut in ????           that sounds like a serious overload  for the vs .

what the gauge shows is just an indication, the fan switch shouldnt be related to the gauges other than visual 

Pete

[Guest]

On 30/08/2019 at 12:48, Brian Sculpher said:

Some month or so ago I changed the temperature sender in order to engage at a lower temperature

Hello Brian,

When you say temp sender, do you mean the SENDER with the wire to the coolant gauge or do you mean the thermal SWITCH that triggers the fan ??

A friend of mine had an incorrect sender unit fitted and the coolant gauge was off the red (!!) without the fan cutting in - a little disconcerting. The sender was replaced with the correct unit and the gauge read perfectly. The temp sender that feeds the coolant gauge will have no bearing on the operation of the electric fan. It is only the thermal switch / sensor that can regulate the fan.

If you replaced the thermal switch controlling the fan, have you installed a switch that cuts in too early i.e. very low heat range ??

I cannot see how a coolant gauge can be wired to trigger an electric fan; it is purely a gauge that is regulated by the temp sender for information purposes only - as Pete has alluded to.

If you have a multi meter with a temperature facility it will be worth comparing the readings:

1- when the fan cuts in and out..................... and I presume you know the thermal switch range ??

2- the coolant gauge reading compared to that of the multi-meter. 

I do not know the TR4A temperature mid-point, but on the Vitesse it is about 85/86 degrees, with the fan cutting in at a higher temperature.

My other observation: is the gauge reading correctly ??

Not sure if the above assists but certainly some points to consider.

Regards.

Richard. 

[Brian Sculpher]

Hello Richard,

Really appreciate your help on this matter, below my additional clarifications.

Recent changes to the coolant system which haven’t caused my latest issue or so it would appear.

Lower rad hose electric terminal which monitors temp, brass fitting changed // Thermostat changed to suit hot climate. Dashboard temp gauge operating correctly and electric fan cutting in when required  at higher temp range (for instance dashboard gauge just leaving normal range) fan then cuts in.

The trigger for my issues appeared when brake/direction indicators failed to include dashboard fuel/temp gauges.                                        

I then ordered a voltage stabiliser which only gave me brake lights and direction indicators. We believed the v/s polarity was therefore positive earth, issued cured by installing a negative earth v/s resulting in everything working apart from the dashboard temp gauge electric fan engaging just prior to reaching the normal operating band.

My concern is the car has warmed up correctly although reached a temp when the fan should normally cut in, despite the dashboard gauge indicating I haven’t reached operating temp.

Trust my info makes sense to you and your additional comments would be welcomed.

Best regards Brian

 

 

 

 

 

 

 

 

[Guest]

Mmmmmmm, an interesting one this Brian !!

At the moment then, we have an electric fan cutting in earlier than you expect and the coolant gauge reading lower than it should. Are these the 2x issues ??

I note you have a high temp thermostat fitted - are you in the UK or a country that actually gets decent sunshine ?? !!

If you are UK why have you gone for a high climate unit, just out of interest ??

At the moment, I think everything is working correctly BUT the coolant gauge is being fed duff information which in turn is giving an incorrect low reading. Looking at your notes you do not say if you have changed the temperature sender and I presume that is located I the thermostat area on a TR4A ?? 

By chance, do you have a known decent working temp sender replacement to swap over ?? These senders should have a colour cap by the terminal - is your sender the correct colour which in turn will relate to its reading output to the gauge.

I'd certainly want to confirm the temp sender is the correct type and doing its job properly.

This would be my next step taking in to consideration the other points you have raised.

Finally and only you can check this via a wiring diagram: do the 2x gauges plus the brake and indicators share a common supply wire at any stage including a common earth point ??

That's the homework for tonight ☺️ !! 

Regards.

Richard.

[JohnD]

First step, IMHO, is to find out what the running temp really is.    As Richard says, senders can go off, especially modern repros.      They are negative-coefficient resistors, which means their resistance falls as they heat up, the reverse of normal materials, so that more currnet flows through the gauge, and the needle rises.      Infra-red pyrometers are quite cheap these days and they can be checked on the kitchen range with a pan of boiling water and a cook's thermometer.    Or Temp-Tabs,  stickers that change colour at a certain temp, eg https://www.ebay.co.uk/itm/Factory-Effex-FX-Mx-3-Temp-Strip-Motocross-Heat-Gauge-Temperature-Stickers-3pk/261903564681?epid=1639285813&hash=item3cfaab3f89:g:dgQAAOSwWmNan3NN  (I have no conection with the vendor)

John

[Brian Sculpher]

Richard, John,

My collective responses as requested.

Hot climate thermostat installed (x 74 degrees C) - as improved aid to cooling this summer. Compatible with thermo switch installed EFC at 82 C on 68 C off. Inclusive of a new radiator cap 7lb 1inch depth to suit TR4 x radiator neck.

The current temp transmitter/sender is colour coded red (this unit has not been changed, adjacent thermostat area TR4) however I am not clear which colour should be installed being now compatible. Spare parts manuals do not also advise a colour requirement!

In respect the wiring links ie; 2x gauges, brake and indicators they are linked by the voltage stabiliser all earthed individually.  

Perhaps with your thoughts, replacements already installed, I should now consider changing my temp transmitter/sender, although I am unsure where I can purchase an operational product? Also looking at purchasing a pyrometer as suggested as a back up water temp re-check

Further comments would be appreciated.

Best regards Brian

 

 

 

 

 

[Guest]

28 minutes ago, Brian Sculpher said:

Spare parts manuals do not also advise a colour requirement!

Hello Brian,

No you are correct, but it will ID the part number which is turn will supply the correct unit whatever the colour cap may be. Have you asked other owners what sender colour cap they have ??

Your fan cutting in at 82 is quite low and then cutting out at 68 - that is a big range difference; I wonder if your fan is cooling the system too early and as such not reaching the correct running temp. Rad cap sounds fine around the 7lbs mark, IF that is what is stated in the WSM.

I suspect the gauge is working okay and reading exactly what the sender is relaying to it.

My question therefore is: are you running your car at too low a temperature ?? It may be worth disconnecting the electric fan once the engine has warmed up (or as best it can) to ascertain if the gauge reads higher. If it does, then without a doubt your fan is cutting in far too early and you need a higher rated thermal switch which in turn will balance a proper reading on the coolant gauge.

If you want to play safe, purchase a digital thermometer to keep an eye on the engine temperature.

Hopefully the above makes sense and is a logical process ??

Regards.

Richard. 

[Guest]

Hello Brian,

I have just checked a number of websites and the sender cap colour is RED, on all of them.

This applies to the TR4 and the TR4A, as you would expect.

With reference to this, I think we may be narrowing the issue to the engine being over cooled with a mixture of the electric fan thermal switch and the hot climate thermostat. If these were rectified and brought in to line, then I reckon the issue may be solved.

Regards.

Richard.

[Brian Sculpher]

Hello Richard,

Yes your comments make sense, although to play it safe I will replace the temp sender first then follow up with disconnecting the electric  fan.

My reasoning for playing it safe is because when the engine appears to reach operating temp followed by stoping and cutting of the engine I can hear water being transferred via the expansion tank and also include a water temp check via pyrometer check.

Really appreciate your and Johns input - will let you know the outcome soon.

Best regards Brian

[Guest]

That's a good move Brian - one piece at a time................................ great song by Johnny Cash, by the way !!

Changing everything at once fails to ID the issue; albeit a number of items may contribute to the actual issue.

Yes, keep the post coming in !!

Good luck.

Richard.

[Guest]

11 hours ago, Brian Sculpher said:

My reasoning for playing it safe is because when the engine appears to reach operating temp followed by stoping and cutting of the engine I can hear water being transferred via the expansion tank

I would expect that Brian. Once the engine is switched off the coolant will no longer be under such great pressure and as such the water will be syphoned; which is the whole idea of a header tank / expansion bottle.

Sounds normal in my book.

Regards.

Richard.

[johny]

usually on stopping the engine the coolant temperature rises due to the heat still stored in the engine and the much reduced means of dissipating it via the radiator so the water expands and the excess is dumped to the expansion bottle. Only when the temperature eventually starts to go down does the water contract and pull back contents from the bottle.