Electrical Woes.
Discussion
My 79 3000M is going through a rough time. The problem this time is with the electrics. When driving, the ignition light illuminates and as a result, I lose partial electrics. On investigating this problem I found that I had lost two circuits all together. The first is the circuit which provides 'Stop lamps, reverse lamps, windscreen wiper, heater, windscreen washer, temperature indicator, fuel indicator' the second is the 'turn signal indicator'.(the voltmeter also reads zero, but the car starts and drives fine) I have took those straight from maintenance manual. It states I should have two fuse boxes, top and bottom, however I have a single fuse box housing four fuses. As I know my hazards work fine, I found the associated fuse and replaced that with the three remaining fuses, all fuses operated the hazards. I removed the fuse box and all connections to it are made and firm. I have found two earth points, one either side of the engine on the chassis rails, these are tight however slightly corroded. I am wondering if there is an earth point further back, perhaps underneath transmission tunnel or towards rear of car that could be suspect too? I am hoping both circuits run to the same fault, so fixing this fault will fix both circuits? fingers crossed!
My wiring is a mess and its on the to do list this winter. The car is booked for its MOT tomorrow but this can be easily cancelled, my main concern is the pre 80's gathering as I wish to attend this in the M and that be the last event before a body off starting in the winter.
My wiring is a mess and its on the to do list this winter. The car is booked for its MOT tomorrow but this can be easily cancelled, my main concern is the pre 80's gathering as I wish to attend this in the M and that be the last event before a body off starting in the winter.
According to the "Theoretical Wiring Diagram", Fuse 1 in the four fuse fusebox system seems to group all of your first items that have failed, and the indicators.
And the second fuse is hazards.
If you've got voltage at the fused side on these fuses, then definitely check earths.
Odd that hazards work but indicators don't, but that could be the indicator flasher unit, but that still makes things confusing with the earths.
Rear lights are notoriously dodgy on Ms due to the rear earth location. If it's the eyelet on the body mounting plate in the boot, then run a new earth into the back. The rear brake T piece bolt is a good spot, or just run a long wire from a good earth up front.
If the temp gauge and fuel gauge aren't working, but you've got voltage to them, then check/replace your engine earth strap, as the earths for these are through the sender and then obviously into the block and then through the earth strap back to the chassis/battery.
And the second fuse is hazards.
If you've got voltage at the fused side on these fuses, then definitely check earths.
Odd that hazards work but indicators don't, but that could be the indicator flasher unit, but that still makes things confusing with the earths.
Rear lights are notoriously dodgy on Ms due to the rear earth location. If it's the eyelet on the body mounting plate in the boot, then run a new earth into the back. The rear brake T piece bolt is a good spot, or just run a long wire from a good earth up front.
If the temp gauge and fuel gauge aren't working, but you've got voltage to them, then check/replace your engine earth strap, as the earths for these are through the sender and then obviously into the block and then through the earth strap back to the chassis/battery.
Edited by Cerberus90 on Sunday 31st August 20:08
Where is the rear earth location? I will check with a multimeter the first fuse point. I thought the hazards were on a seperate circuit, the 'turn signal indicator' on a circuit of its own? I have a relay for hazards and relay for indicators, I've switched them round and they both seem to be working fine.
The frustrating thing is everything is wired up but I have half as many wires again running alongside the loom which aren't connected to anything. The wiring loom is so tight that any slight tug is enough to brake a corroded connection. I really need to solve this.
The frustrating thing is everything is wired up but I have half as many wires again running alongside the loom which aren't connected to anything. The wiring loom is so tight that any slight tug is enough to brake a corroded connection. I really need to solve this.
DAKOTAstorm said:
Where is the rear earth location? I will check with a multimeter the first fuse point. I thought the hazards were on a seperate circuit, the 'turn signal indicator' on a circuit of its own? I have a relay for hazards and relay for indicators, I've switched them round and they both seem to be working fine.
The frustrating thing is everything is wired up but I have half as many wires again running alongside the loom which aren't connected to anything. The wiring loom is so tight that any slight tug is enough to brake a corroded connection. I really need to solve this.
You may have damaged wiring in the little incident the other week I really hope you get her sorted to get to the pre 80S looking forward to meeting you there.The frustrating thing is everything is wired up but I have half as many wires again running alongside the loom which aren't connected to anything. The wiring loom is so tight that any slight tug is enough to brake a corroded connection. I really need to solve this.
I would be looking in that area first heat can do all sorts of things to wiring particularly old wires
Andrew
DAKOTAstorm said:
Where is the rear earth location? I will check with a multimeter the first fuse point. I thought the hazards were on a seperate circuit, the 'turn signal indicator' on a circuit of its own? I have a relay for hazards and relay for indicators, I've switched them round and they both seem to be working fine.
The rear earth will be somewhere in the region of the fuel tank area. Depends whether a previous owner has done any modifications to it.Indicator/Hazard circuit, the wiring diagram picture I'm looking at may not be accurate, and again, depends on what a previous owner may have done. The indicators/hazards are different circuits sort of. The feed for the hazard flasher will most likely come from a permanent live fuse, then go to the hazard switch, which then goes on to the Left/Right lights. Indicator flasher unit feed will most likely come from an ignition switched fuse, then goes to the indicator stalk (or hazard switch again depending on which hazard switch is fitted).
Well I have cleaned up all earths to a shine, the two either side of engine and the one near fuel tank. I have checked all fuses and all connections are made and tight, yet the problem still consists. With no clue as to what is wrong and the car outside of it's MOT I will have to miss the pre 80's. On top of this I strained ligaments in ankle and can't put weight on foot never mind press the clutch!
Have you checked to see if your alternator is charging? If the ign light is coming on while driving, then that would suggest that the alternator has stopped producing any output.
Have you lost all these circuits all the time now, or is it only after you've been driving for a while and the ign light comes on?
Wonder if it's the ignition switch, seeing as the circuits that you lose seem to be ignition switched circuits.
When ours on the 1600M got worn, the bouncing/bumping of the car could make the key wobble in the barrel enough to turn the ign off.
Have you lost all these circuits all the time now, or is it only after you've been driving for a while and the ign light comes on?
Wonder if it's the ignition switch, seeing as the circuits that you lose seem to be ignition switched circuits.
When ours on the 1600M got worn, the bouncing/bumping of the car could make the key wobble in the barrel enough to turn the ign off.
The rear earth is outside the car ...using a anti-rattle washer digging into the chassis and as such permanently loose! as the OE design from 1972 of metal plate packers between the shell and the chassis as spacers gets 'forgotten' somewhere along the production process and replaced by rubber packers (allowing it to be loose!!). IMHO you need to replace the earth with a link wire from the plate/bolt and attach a new earth to the 3 way brake fitting on the chassis.
The TVR theoretical wiring diagram (that is often quoted as THE diagram) finishes at chassis 4435FM, BUT, do you have the positive negative posts on the bulkhead? if YES then dismantle them cleaning the brass bolt, then soldering the Lucar connectors to the bolt head, replacing all of the connections and the wax separator card, so that the internal/front/rear of the loom is good.
Purchase some concrete cleaner !! (Wickes/B&Q) hydrochloric acid !! SO gloves/goggles (OR tomato sauce...LOL) and remove the fuse box and bathe/clean/toothbrush it (OR buy a new one and modify it to match the OE item by soldering the links on the back (that way you have one 'READY' to swap into the car as the one in use corrodes!! THEN, you can treat the fuse box as a service item to be swapped onto the car every so often).
DO NOT use fuses with plate internals..find wire versions.
Adrian@
The TVR theoretical wiring diagram (that is often quoted as THE diagram) finishes at chassis 4435FM, BUT, do you have the positive negative posts on the bulkhead? if YES then dismantle them cleaning the brass bolt, then soldering the Lucar connectors to the bolt head, replacing all of the connections and the wax separator card, so that the internal/front/rear of the loom is good.
Purchase some concrete cleaner !! (Wickes/B&Q) hydrochloric acid !! SO gloves/goggles (OR tomato sauce...LOL) and remove the fuse box and bathe/clean/toothbrush it (OR buy a new one and modify it to match the OE item by soldering the links on the back (that way you have one 'READY' to swap into the car as the one in use corrodes!! THEN, you can treat the fuse box as a service item to be swapped onto the car every so often).
DO NOT use fuses with plate internals..find wire versions.
Adrian@
Edited by Adrian@ on Friday 5th September 12:55
Surly if you just started at the beginning of the circuit ie batt turms. And with ing and faulty items turned on follow circuit through with voltage tester and find out ware it drops ! You need to work out if you have a earth fault or power supply fault. A meter will tell you but as an aircraft engineer I'm sure I'm teaching my g mother to suck eggs. Richard. Good luck.
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