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MG TD TF 1500 No brake lights BBS discussion at MG-Cars.net
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MG TD TF 1500 - No brake lights
| My brake lights on the TF are not working. The last time I had this problem, I replaced the pressure switch and also added Dave DuBois' relay circuit. I just shorted out the terminals on the pressure switch and there was still no brake lights. I assume that if the relay circuit was OK, the lights would have come on. If they had come on I would assume the switch was bad. This means the relay wiring is bad. Is my logic sound? |
| Ron Coates |
| Yes, assuming you've already verified there is 12 volts at the switch. There is also the possibility of a bad connection or connector, or a damaged wire. Or even two bad bulbs. I've seen it happen! If you don't have a spare bulb on hand, just measure for voltage at the socket. |
| Steve Simmons |
| Test lamp on the contacts of the switch, with ignition on, one should have 12V. If not head forward back to the fuse. Peter |
| P G Gilvarry |
| Do the turn signals work? Lonnie TF7211 TF681 |
| LM Cook |
| Swop to led brake lights and you don't need the relay. Dave H |
| Dave Hill |
| Lonnie - turn signals work Dave - what is involved installing LED lights? |
| Ron Coates |
| Turn signals work then the A3-A4 fuse must be intact. Test lamp on the terminals of the switch next, looking for 12V on the wire coming from the front of the car. Peter |
| P G Gilvarry |
| Very easy to change to led bulbs, once you know the type of bulb fitting. Its a fit and forget solution. These bulbs draw very little current, putting minimal stress on the brake light switch. Dave H |
| Dave Hill |
| Check you have voltage at T5 at the relay box when you brake. If not then bad connection between brake switch and T5. If you have, then probably relay switch contacts faulty. Ray TF 2884 |
| Ray Lee |
| Ron,
Attached is the wiring diagram of the brake light relay mod. The good thing about relays is that you can hear and/or feel if they are (partially) working. With the ignition on, put your finger on the relay box, get a helper to press and release the brake pedal a few times, check for a click. This only verifies the coil driving circuit. With a test lamp or meter you will need to check the switching circuit. If the relay does click then, with the meter, or lamp and the pedal pressed check that you have 12volts at the green/purple wire. If so then the relay mod and the brake switch are working correctly. John  |
| J Scragg |
| Dave H I have looked back in the archives and I can determine the socket type by removing one of the bulbs. There is a lot of talk about polarity. My TF is positive ground. Who sells LEDs for positive ground? |
| Ron Coates |
| What have others used? |
| Ron Coates |
| I have just realized that the rear light bulbs are dual filament - one for regular rear light and another filament to add brightness when braking. Are LED bulbs made to do both jobs? Again, anyone, what have you used to do this, especially for positive ground. Who sells them and what part number? |
| Ron Coates |
| The rear lamps house an 1157. Classic Car LEDs in the UK are a great source. Make a decision on whether you are going to stick with positive earth and subscribe to the flat earth society, or step into the 20 century. There is no reason to stick with positive earth unless you have invested heavily in LEDs or electronic fuel pumps etc. It takes under 30 minutes to step into the real world of negative ground, however you can get LEDs in either gender. Peter |
| P G Gilvarry |
| Ron, the LED taillight "bulbs" I got from Little British Car Co. don't care about polarity, have the LED equivalent of dual filament and are low priced. I've had them in my '53 TD for a couple of years with no issues. The only problem I had was that they were a bit longer than the standard incandescent so, not being a stickler for originality, I changed the tail light lenses to the lenses for a frog eye sprite. My friend's '51 TD has the rectangular tail light and there was no fitment problem. I don't know how the taillights on a TF are shaped.
Jud |
| J K Chapin |
| All,
I am confused about the information on the LED conversion for the rear brake/direction indicator lamps. From your messages it appears that it is a direct replacement. For this to be the case one of the following conditions are required. 1/ The led has an internal shunt resistor to make it consume 21 Watts 2/ The standard flasher unit has been replaced with and electronic version. Without one or other, the frequency of the flasher would be incorrect. Here is why. The original type flasher unit uses a bimetallic strip to switch, and is calibrated to flash correctly at 42 watts (2 X 21) any other load will give an incorrect frequency. If the LED has a shunt resistor, then the circuit draws the same current as the original filament lamp, meaning that the brake light switch will be as stressed with the led circuit as the filament circuit. John |
| J Scragg |
| John, Most people swap the flasher, Classic Car LEDs in the UK does one that works. Plug'n'Play, Also, their LEDs fit into the regular lamp. Peter |
| P G Gilvarry |
| John, you are right. I should have mentioned, I swapped the resistance flasher for an electronic flasher. External dimensions and electrical connections are the same Gives the proper flash rate and hast the "click" which can be heard at idle but not at any speed. |
| J K Chapin |
| John, you are right. I should have mentioned, I swapped the resistance flasher for an electronic flasher. External dimensions and electrical connections are the same Gives the proper flash rate and hast the "click" which can be heard at idle but not at any speed. Jud |
| J K Chapin |
| Jud, That now makes sense, thanks for your response. John |
| J Scragg |
| I removed the relay circuit and wired it back to original and the lights worked. I have decided to fit LED bulbs. The TF lens is red. My incandescent bulb is clear. LBCco says I should fit a red LED not white. They don't have white positive ground. Is it right to fit a red LED? |
| Ron Coates |
| Yes red LED in a red lense is the normal way to go. Peter |
| P G Gilvarry |
| Thank you all for your input. |
| Ron Coates |
| Electrical gremlins can be tough to solve, a simple test lamp, preferably incandescent can go a long way to help.
I made a simple one from a taillight socket, single filament lamp and clips with a few feet of wire. Why not LED? On our cute little cars some are still positive earth and all LED test lamps are designed with the clip on the negative ground side. Test lamps with incandescent bulbs draw current, most modern volt meters don’t, so a dodgy connection may carry voltage but fail when required to carry current. My little 2 clip test lamp acts as a generator test lamp, one clip on the D terminal, the other clip on the LIVE side of the battery. Start the engine, at idle the lamp will be illuminated, dims as RPM increases and extinguish about 1200RPM. An LED will light even when the generator output is maybe 8 bolts as they can work down to 5 bolts or so. A great asset in any tool box. Peter |
| P G Gilvarry |
This thread was discussed between 22/06/2022 and 28/06/2022
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