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Ignition - Electrical Troubleshooting


Skip

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I had to replace the starter on my 1984 911 a couple of days agom started up great. Later I replaced some of the instrument bulbs and an interior dome light. Went out this morning to start her up but could smell that lovely burned electrical smell. Inserted the key and nothing - no oil warning light no radio light no click - just silence. Checked the fuses and one was blown but the strong smell was inside the car predominately. Pulled the electical harness connector off the back of the ignition switch and confirmed voltage on the two posts marked with "30" as per the manual. Checked some continuity to the radio etc from the electrical harness connector and there is continuity. I've read a couple of the other posts ref corrosion on the fuse points but that doesn't appear to be it. I'm not sure if there is an easy test to see why absolutely nothing is functioning - is that a sure sign of a particular fault (less the smell)?

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What is the state of battery charge? What circuit had the blown fuse?What was the original fault with the starter that caused it's replacement?

The battery is at 100% charge - no problems that I can see there.

The blown fuse was the power windows fuse, but I believe that was an error on my part working on a trim issue where I forgot to disconnect the battery terminal.

As for the starter, the benix I think it's called (solenoid?) was disengaging after start up and therefore was grinding with the fly wheel kicking it out. The car started perfectly with no grind after installing a reconditioned Bosch starter that I bought from Pelican.

I'm also trying to figure out what battery type is supposed to be in the car. The manual I have says 88 amp hours, but that's all. When I try to go to buy a battery, I'm asked what are the cold / warm cranking amps required, and I can't find that information anywhere (no sticker remaining on the battery I have. Am currently trying to charge the battery.

Edited by Skip
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I'm worried about this "electrical smell" you mention. Re-check the fuses using a test light. The fuse array in the older P-cars is famous for looking fine but not conducting current due to corrosion at the fuse tips. With the ignition key on test for power at both ends of the fuse, if you have power at one end but not the other the fuse is open or a poor connection.

As for the battery, you should be more concerned about the group size. The correct group size will have somewhere around 650 CCA. Be sure the battery cables are sound and no poor connections at that end.

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I'm worried about this "electrical smell" you mention. Re-check the fuses using a test light. The fuse array in the older P-cars is famous for looking fine but not conducting current due to corrosion at the fuse tips. With the ignition key on test for power at both ends of the fuse, if you have power at one end but not the other the fuse is open or a poor connection.

As for the battery, you should be more concerned about the group size. The correct group size will have somewhere around 650 CCA. Be sure the battery cables are sound and no poor connections at that end.

OK thanks. I'll test each of the connections on the fuses in the morning. I managed to charge the battery to about 50% and used the charger start feature to get it going - that part seemed to work but the headlights do not - I think that's the area under the dash where the smell is. I have disconnected the battery negative terminal until I can check it in the morning, so I don't short anything else nor kill the battery either.

I noticed several wires leading to the positive terminal as well, so will tidy those up also and trace them back as I expect they are after market additions but should go through fuses either way if they don't have inline ones.

Based on the fact that the fuses are the old bullet type, is there a way to change them to more modern ones or is that tempting fate also?

For the battery, I'm not sure what you mean by "group size". I understand the 650 CCA however.

Thanks so much for your help - I am enjoying this regardless.

Edited by Skip
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Batteries have a group size relating to their physical size,mounting tab/tabs,top post or side post and post location,etc. There is no way to upgrade to a ATO style fuse block that I know of. You can put dielectric grease on the fuse tips and re-tension the fuse tabs also. Best of luck with it all and let us know how it turns out.

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Batteries have a group size relating to their physical size,mounting tab/tabs,top post or side post and post location,etc. There is no way to upgrade to a ATO style fuse block that I know of. You can put dielectric grease on the fuse tips and re-tension the fuse tabs also. Best of luck with it all and let us know how it turns out.

Thanks. Will do.

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Batteries have a group size relating to their physical size,mounting tab/tabs,top post or side post and post location,etc. There is no way to upgrade to a ATO style fuse block that I know of. You can put dielectric grease on the fuse tips and re-tension the fuse tabs also. Best of luck with it all and let us know how it turns out.

Thanks. Will do.

OK, so I checked the fuses and they seem to have power on both sides of the fuse, did some housekeeping none the less however (also noticed some higher than allowable fuses in some areas, which I corrected to specs).

Removed the headlight switch and voila - source of that glorious burned electrical smell - see attached picture (not a pretty sight). Have cleaned up and replaced the end connectors to the wires which were attached and have noted the locations of each - however based on the fact that something shorted out, I'd love to know exactly what fits where to ensure they're connected correctly. I have checked my Bentley shop manual and can't seem to find a specific reference that sould show the back of the plug with some 10 connections (that I can notice due to minor meltdown). The car starts up fine still without the switch, but of course none of the lights work without it. Best location for buying another one - any ideas?

post-49895-1257983502_thumb.jpg

Edited by Skip
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Hi I'm glad you sorted it out. I am trying to remove the starter from my 1986 carrera 3.2.

I have removed all the wiring and slackened the lower fixing nut but I cannot get a spanner in on the top fixing.

I should be very grateful for any help on how to remove the starter motor.

Thanks Lionel

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If I remember correctly, the upper starter bolt is a 12mm allen type socket.

Hi Thanks I kept feeling around looking for a 17mm nut the same as the lower fixing. I now know what to feel around for.

Many thanks wvicary.

Regards Lionel :D :renntech:

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If I remember correctly, the upper starter bolt is a 12mm allen type socket.

Hi Thanks I kept feeling around looking for a 17mm nut the same as the lower fixing. I now know what to feel around for.

Many thanks wvicary.

Regards Lionel :D :renntech:

Mine was a 10mm Allen Wrench on a 3/8" socket that I used. The only way to easily access (somewhat sarcastic) the upper bolt was over the top of the transmission - seems odd, but there's a heck of a lot more space than directly from the front. This way I could guid the socket into place by feel rather than simple trial and error.

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If you didn't have a fault with the headlights or switch before this don't you think the fault might be in the area of the bulbs you replaced? Maybe something got connected wrong when you changed out the instrument bulbs.

I guess that's possible, but I don't recall changing any wires or plugs per say, just added the small bulb into the socket that was fit into the back of the tachometer and high beam light. They worked appropriately when I put them in. There do appear to be some connectors floating around that don't appear to have a home (so I've placed electrical tape across them until I can trace them either by the wiring diagram or manually over the winter.

I've also ordered a replacement switch via eBay (US $40 vice $205 at other store site) - hope it works out - same part number and all.

Would you know the correct positions for each of the wires that come off the back of the light switch? I was deliberate in marking them, but some were "fused" to say the least.

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If I remember correctly, the upper starter bolt is a 12mm allen type socket.

Hi Thanks I kept feeling around looking for a 17mm nut the same as the lower fixing. I now know what to feel around for.

Many thanks wvicary.

Regards Lionel :D :renntech:

Mine was a 10mm Allen Wrench on a 3/8" socket that I used. The only way to easily access (somewhat sarcastic) the upper bolt was over the top of the transmission - seems odd, but there's a heck of a lot more space than directly from the front. This way I could guid the socket into place by feel rather than simple trial and error.

Hi Skip. Thanks for your reply. Yes mine happens to be a 10mm too. Phew what a job! I still havent managed to get the allen bolt loose.

I have tried with the 3/8 sockets but it is to tight to move. I bought a 10mm 1/2 socket but the long extension is to long and of course the short extension is to short??

I dont know where to go from here Ill have to try and think of some thing.

Thanks again Lionel

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If you didn't have a fault with the headlights or switch before this don't you think the fault might be in the area of the bulbs you replaced? Maybe something got connected wrong when you changed out the instrument bulbs.

I guess that's possible, but I don't recall changing any wires or plugs per say, just added the small bulb into the socket that was fit into the back of the tachometer and high beam light. They worked appropriately when I put them in. There do appear to be some connectors floating around that don't appear to have a home (so I've placed electrical tape across them until I can trace them either by the wiring diagram or manually over the winter.

I've also ordered a replacement switch via eBay (US $40 vice $205 at other store site) - hope it works out - same part number and all.

Would you know the correct positions for each of the wires that come off the back of the light switch? I was deliberate in marking them, but some were "fused" to say the least.

Hi Skip I have a wiring circuit that may be of some help . Hope I can get it to copy ok .

Regards Lionel

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If you didn't have a fault with the headlights or switch before this don't you think the fault might be in the area of the bulbs you replaced? Maybe something got connected wrong when you changed out the instrument bulbs.

I guess that's possible, but I don't recall changing any wires or plugs per say, just added the small bulb into the socket that was fit into the back of the tachometer and high beam light. They worked appropriately when I put them in. There do appear to be some connectors floating around that don't appear to have a home (so I've placed electrical tape across them until I can trace them either by the wiring diagram or manually over the winter.

I've also ordered a replacement switch via eBay (US $40 vice $205 at other store site) - hope it works out - same part number and all.

Would you know the correct positions for each of the wires that come off the back of the light switch? I was deliberate in marking them, but some were "fused" to say the least.

Hi Skip I have a wiring circuit that may be of some help . Hope I can get it to copy ok .

Regards Lionel

Sorry about this, I just cant get the diagram to show. I have uploaded it , it dose not show anywhere.

Lionel :huh:

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If I remember correctly, the upper starter bolt is a 12mm allen type socket.

Hi Thanks I kept feeling around looking for a 17mm nut the same as the lower fixing. I now know what to feel around for.

Many thanks wvicary.

Regards Lionel :D :renntech:

Mine was a 10mm Allen Wrench on a 3/8" socket that I used. The only way to easily access (somewhat sarcastic) the upper bolt was over the top of the transmission - seems odd, but there's a heck of a lot more space than directly from the front. This way I could guid the socket into place by feel rather than simple trial and error.

Hi Skip. Thanks for your reply. Yes mine happens to be a 10mm too. Phew what a job! I still havent managed to get the allen bolt loose.

I have tried with the 3/8 sockets but it is to tight to move. I bought a 10mm 1/2 socket but the long extension is to long and of course the short extension is to short??

I dont know where to go from here Ill have to try and think of some thing.

Thanks again Lionel

The only thing I can think of is perhaps an impact wrench (air compressor type to loosen) or a multiple of short extensions on the 1/2" drive). Just be careful of course. You'll probably need to use a universal joint as well.

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here is what I have

Thanks magcuda (and thanks for the efforts Lionel). Will be going to town on this as soon as my part arrives in the mail, but will trace the wires to ensure they have no shorts in the meantime.

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