HELP PLEASE - All electrics gone

[Amazoner]

hi all,

I have a 1967 121, with an ignition switch that is used to switch the car on, and a push button to start the car, installed by a previous owner.

In the morning I started her up fine, filled her up with petrol, parked her outside (no rain) ready for a nice long drive. Two hours later, I switch her on and absolutely no electrics working at all - no instruments, no lights nothing.
But when the key is in the on position - she still starts and runs perfectly well, using the push start button.

My immediate thought was a fuse, but checked the fuse box and all was fine.

My next check was the battery terminal, but given she turns over perfectly well, I can't imagine that would be it. I did loosen and retighten the terminals.

My worst fear is the ignition switch has failed and needs replacing, but why then does the start button start the car when in the on position?

I understand that if one electrical component goes, it could affect the everything, so I guess it could be anything.

If anyone can give me advice on how to solve it or where to start looking, i would very much appreciate it.

Thanks all,

[Ron Kwas]

(Formerly, but hoping to soon be again) Amazoner;

Your e-mail was written in obviously some stress, so first I will recommend that you take a deep breath, relax, and know that these vehicles had simple, electrical systems constructed with quality components, (occasional) failures of which can always be figured out and remedied...and you've come to (one of the) right places for that!

That having been said, it can't be "anything" but the symptoms do suggest a possible failure of one part of the ignition switch...the contact which supplies terminal 54 ...(all Ignition powered loads)...when key is in Position 3...as shown here...

Source: http://www.sw-em.com/Ignition_Additi...llast_Resistor)


The diagram abobe shows standard unmodified Ignition switch and functions...with Push-Button Start Switch (PBSS) installed (if it is one of mine), circuit should look like this:



(Source: http://www.sw-em.com/starter.htm )

I recommend you verify Ign Sw terminal 54 is not supplied with power when key is in Pos 3. (a failure condition)...and we will have to proceed from there...

...but you also stated "no lights"...I have to presume by that you meant no Instrument panel lights when turning key to the Ignition ON position, because if you meant no Headlights, it will get more complicated...please clarify!

Other than PBSS, can I presume vehicle electrical system is unmodified?

Entire vehicle wiring diagram: http://www.sw-em.com/122S%20Wiring%20Diagram.jpg
...remember: the color code as shown on wiring diagram is your friend!

Good Hunting from Connecticut!

[Amazoner]

Hi Ron,
Firstly, thank you for the very helpful reply.
Unfortunately and much to my frustration, it will be only Sunday when I can get back to my car and reconfirm symptoms and test the ignition switch.
It seems as though all ignition loaded instruments are not getting power, but am almost certain the headlights and indicators didn't work either, but I really need to reconfirm that on Sunday.
from what I've seen, the electrical system is all original and unmodified other than the PPBS.
I will post more info as soon as I can.
Thanks again for the helpful details.

[Ron Kwas]

Amazoner;

...in thinking about this a bit more, I came up with another question: If PBSS is wired as it should be (as shown in second diagram), it is powered by terminal 54, but your symptoms suggest this terminal is not supplying power to other Ignition loads...this is a big inconsistency!...so what powers PBSS in your case?

A few minutes behind dashboard and at the terminals of Ignition Switch with a voltmeter should clarify this. I suggest you measure and report voltages at terminals 30,54 and PBSS under all key positions, (while obviously taking note of any loose wires, terminals or other unusual conditions).

Also, confirm that Headlights are not powered (irrelevant of Ignition Switch position!)...these should be Battery powered...so as long as Battery is charged and connected, should work...if they don't, something else is amiss...

Good Hunting!

[Volvorama]

Could it be the little fat fuse at the top of the fuse box (25 amp)? If this goes you still have headlights and sidelights but little else. They are not stocked by motor factors so many people wire a blade fuse across the fuse terminals. If the fuse is ok bad connections in the fuse box itself are common so try by-passing it.
Good luck.

[Amazoner]

Well, it ended up being a simple bad connection on the dumpy/fat fuse, so I can only thank you Ron and Volvorama for the advice, and apologise for wasting your time.

Of course am delighted it was an not an ignition switch failure. The frustrating thing is - I had checked the fuse box on the day of the issue, but I guess that check was rather rushed - given my wife was tapping the foot, plus I had actually replaced that fuse and cleaned all the connections a week earlier.

I guess the other thing that initially threw me off was the fact that the PBSS was still getting power when the key was in the ON position.

My first check today was the headlights and parklights, they worked fine.

Looking at the ignition switch wiring, to me it corresponds to the modified ignition switch diagram that you included Ron, but this was a quick check, and given my track record...

Ron - since it was the dumpy fuse causing the issue, is there still an inconsistency that the PBSS got power at terminal 54?

thanks again

[Volvorama]

Thought it might be that. Very common fault. Often it's the fuse box itself that causes problems. If you don't want to buy a new one 940Turbo would solder the riveted joints to get a good electrical connection back.
I've also done the push-button starter thing on many cars, often before the switch starts acting up because it reduces the number of keys that get broken. I leave the switch alone and wire a button switch in parallel with the original circuit. Handy in those stalled-on-a-level-crossing moments when turning the key is the first thing that comes to mind....

[Volvo Canadian]

Hi Mark, if I may add a question to this thread....

I have a loose contact/rivet connection on my fuse box. Tried soldering it by heating the tab with a propane torch then applying solder. No-go, although there is flux and the heat was enough to melt the solder.

[Derek UK]

The area has to 100% grease free/clean. Brake cleaning fluid is good. Wire brush the area. Some good plumbers flux and a heavy duty iron is usually enough to do the trick so not normally any problems. In the UK there is Baker's Fluid which is an acid based flux but I don't know if it is called the same over there. It usually works like magic.

[Tail]

I just put in a new fusebox due to some fluctuating electrics, I think it was around £20 from Brookhouse and 30 minutes to change over, a vast improvement. Has anyone ever found a good way to clean the inside of the spade connectors, some of which are looking a bit grimy and several needed a small crimp as they were surprisingly loose. A cut down nail file perhaps would do the job, wire brushes just don't seem to get right in there.