DDK - Die Deutschen Klassiker

There is always something on these old cars, and I have 3 to iron out, but maybe someone can give me a 'short-cut' to 3 solutions.
1
The car has a healthy 3.2 in it, 140K miles (maybe more) and on start-up and just running there is a loud resonance from the rear of the car, RH side. After a few seconds/blips it clears, runs perfectly. Silencer resonance? Starter motor running on?
2
Indicators. Never ever been right for the 31 years the car has been on the road with me. Left turn, green arrow on dash flashes correctly and goes out, winker carries on until cancelled. Same with the left. Relay? Each light unit has a fresh separate earth.
3
Oil pressure light. For 31 years perfect then it would go to 140 psi and stay there.no matter the revs.
Now, sometimes it will suddenly drop to the correct value, but it might just to a max of 140 and stay there. All wires bell through from the new sensor to the back of the gauge. Earth is good from gauge to chassis.
Any ideas?

2: I'd suspect inadequate bulb wattage. If your indicators have ba15s or ba15d bulbs try a headlamp bulb as a test experiment. You will need to source one with the correct base format vs filament format...if they're bay15d (offset pin) just file 1 pin off the test bulb. 1 bulb will give you an answer....Sorry but I'm unfamiliar with the bulb layout on a 911. W

Sent from my SM-G970F using Tapatalk

Thanks for the idea.
Hope to delve into the gauge and blinkers tomorrow morning.

Fooling around with 12volts in the hard sun is no fun.

Oil pressure gauge:
Belled the wire through from the engine sender (new) to the back of the instrument and all is well.
Gauge bells to ground too, so I think this must be:
Faulty new sender
Faulty/intermittent gauge.

While running sometimes the reading will drop from 140 psi (full scale deflection) to 60 psi (hot engine, 2200 rpm), then after some time (inconsistent) it will jump up to 140 again.

I think it will be going to Reape instruments later in the year.

The indicators all seem to work except the dash green arrows which stop flashing after about 3 flashes but the indicators still flash.
The relay is a large Hella, original to the car.
Pricey! So will leave that to the autumn too....

Next is the odd vibration noise on start up from the region of the starter motor. The noise can last 2 seconds or about 10 and does not change with blipping the throttle.

I had the same issue with the indicators, but mainly only when it was wet.

During the rebuild I rewired the lamps front and rear and created new earth leads for the rear direct from the bulbs rather than via the housing.

Obviously as I changed too main things at once I don’t know the true root cause, but I’d put good money on it being the quality of the earth connection on one or more of the lamps.

Thanks, I did make up new earths from each housing, but not directly from the bulb.
Did this while re-building the shell 2 years ago, made no difference. Car has been like it since 1990.

Need to delve deeper.

I wonder if you can blow dust out of the relay, clean connectors... even run it through the ultrasonic cleaner at a low temp before you try replacing it.

It could also make sense that something is heating up, e.g. corroded wires to the dash bulbs, dashboard earth.

Sent from my SM-G988B using Tapatalk

Rob, the Hella relay runs the hazards and the indicators, and clicks a dream while either switch is enabled.
The actual indicators work, hazard or side to side, but the green light on the dash stops flashing after a few seconds, so, you can be going down the road with the indicators working. Got flashed a few times recently for this.

With the hazards on, the indicators all work simultaneously and so does the red light in the push switch for as long as they are asked to work.

My thinking was, if the lights work and the dash lights don't, there must a mechanical switch within the relay which breaks two circuits simultaneously. There may even be two pairs of contacts opened and closed within the relay.

One contact could be clean and the other dirty - hence cleaning inside the relay as well as the contacts.

Otherwise, there could be some unwanted resistance in the dash circuit. It's not enough to darken the lights when cold, but after the wires warm up after a few seconds of current and their resistance increases, it darkens the light. For the circuit to be warming in two or three seconds and cooling again, the wires would have to have deteriorated and there would have to be a thin, resistive length of wire carrying the current.

Not the answer you want, but my money would be on the relay.

Sent from my SM-G988B using Tapatalk

The flasher relay uses the current feed to the lights (via column selector), to energise a secondary solenoid coil inside the relay, that closes a second contact just for the dash bulb.

They is a blue wire on the flasher relay. Check that is pulsing 12v (feed to dash bulb) when the lights are activated.

If that doesn’t pulse, the relay may be tired or perhaps you are using led bulbs that don’t pull enough current.

Understand your thinking Rob. I have a few planned trips locally/Oulton Park etc coming up so need to keep the car 'going' so reluctant to open the relay, though new are readily available via Design 911 etc. The top cover is simply glued on mind, so easy to split etc.
Looks like a job for today.
This fault has been with the car since the early 90's, but still irritating.

I'll test the pulse as you say Mike, easy to pull the gauge and get a meter on it.
I did try to 'led' the instrument lights some years ago all to no avail, and this indicator fault was one of the reasons I removed the led's and back to those small bulbs as standard.

Oil pressure gauge more important mind...

Sorry meant if you are using led indicator lights on the outside. It’s the current to those lights that powers the relay switch for the dash bulb. The dash bulb grounds via the exterior bulbs too, not a direct earth at the dash, which add to the complication

Thanks Bruce, maybe this message might get the brain going ...

Just spent 2 hours on the 911 indicator issue.
As a start, the ign on (all gauges alive) and rh ind all ok inc the green

arrow light. would run correctly for minutes/getting bored watching.

LH ind 2 green flashes, then nothing on the dash, car indicators working for ever.

Pulled the tach out and found one wire to the LH green bulb off the light terminal. Replaced it.

Now had RH ind on and both green arrows flashing for ever.
LH green, 2 flashes then nothing on the dash, ind all working.

Hazzards all ok.

Removed the Hella 1973 relay and opened it up (simple clip top). First time this has been disturbed since doing the LHD to RHD conversion in 1993.
Cleaned the 4 external contacts, and 800 grit paper cleaned the relay contacts. Only one relay, circuit looked good, no hot/burnt smells and so put it back in.

No change, 2 greens to the right, 2 flashes only on left.

Took the indicator switch out and washed the contacts with brake cleaner, moved the lever a lot while cleaner dried off. Put it all back together.

Nothing changed!

My conclusion from all this is the relay is faulty.
Anyone concur?

Next will be the pressure gauge which could be trickier to evaluate.

Have you tried to change the flashing bulb in the left hand green indicator light arrow, it may have an intermittent break in the bulb filament, which just gives up once heated, then connects again when cooled down, hence only 2 flashes and gives up?

No, have not tried that, BUT when the rh ind is on, both bulbs flash , both the same intensity too. I tested the lh bulb in it's holder for continuity, all ok, but certainly thanks for the thought!

As to the oil pressure gauge.

This must be a simple fix?
And indeed it was.
I kept the old sender (by the fan) which I replaced and 'helped' the condition of the loom and the engine/loom connection etc. about 12 months ago.
Changed it for a new Classic Porsche part, gauge has been intermittent since (about a year now)

Connected the old sender to the engine wire, and the thread to ground. Turned the ignition ON and the gauge flicked to 10 psi, ie he bottom of the scale. Started the engine, and it read 50 psi tickover/cold just like it always has.
A few blips and the gauge goes up and down just like it used to.
This is exactly how my LOLA gauge responds.

Removed the new sender and fitted instead another new one/spare off my LOLA race 3.2 which uses a much larger thread fitting.
Grounded the thread, connected the loom, gauge working as with the original old one.

Fitted the old sender back on the engine and the oil lines, bit of a faff, but got there (hot engine and it's 22.5 here).
Restarted the engine, all is well, indicators still misbehaving!

Some progress, but i think I'll buy a new relay and cross my fingers.