Speak Up ...

[bob12]

I have mentioned previously a 'little' problem I have been experiencing with my door speakers on my '90 745 over the past year in that the fronts/left/right and wherever cut out randomly.

I have learnt that a trick to get them functioning again (if albeit temporarily) is to just tap the door mirror or window operating switch.

Having done a couple of hundred miles or so over Christmas in some terrible weather conditions I have found that even operating the wipers or switching on the headlights (amongst others) makes the speakers all cut in again for a long or short time.

I am beginning to conclude that as the problem seems to be associated with a change/spike in voltage that a poor earth connection at the radio/loom/speaker by-pass wiring (or elsewhere!!) may be the culprit.

Any ideas?

Bob.

[Laird Scooby]

Your beginnings of a conclusion is where i'd start looking first Bob, if you have the original radio and separate amp, check the earths on both of those, also check the DIN plug connections between them.

Also worth checking the fuses that supply the radio etc - they're obviously intact but they could be dirty on the blades or have vibrated loose (more common than you think in those fuse boxes behind the ash tray!) but also worth checking the speaker wires haven't become entangled with the window regulator mechanism in the doors - that can cause the same problem.
It causes the amp outputs to short out so the amp goes into shutdown, when a voltage spike happens, it sees a reset and starts working again.

Obviously that last bit depends on the sensitivity of the amp safety circuits but some are sensitive enough to do that.

[bob12]

Thanks Dave. The CR-702 was ditched a couple of years or so ago and I now have a very modern headset with 'all the bells and whistles' (hands free/sd/etc).

To update the existing wiring to ISO without tampering with the loom plugs and wiring I used the correct Autoleads wiring set which included the amp bypass wire.

One of the ISO sockets on the head unit connects to the existing loom socket for power/electric aerial etc. The speakers are fed direct from the head unit built-in amp via the ISO plug which plugs into the original multi-plug that used to be connected to the original amp. The original amp does not connect with anything. So the set-up is fairly simple as none of the wiring has been hacked about.

When the weather improved I really will have to get out and sort it out, but for the present I shall keep tapping the mirror switches!!

Bob

[Laird Scooby]

That's handy Bob - i take it the new head unit has a "Mute" button? If so, next time the speaker(s) dies hit the mute button without tapping the mirror or window switches. Give it a short while (30 seconds ish) and press the mute button again to unmute the speakers, if all 4 come back, there's a wiring short probably in the doors and i'd hazard a guess the speaker wires have been chewed by the window regulator mechanism.

Could also be between the doors and the body, easy way of checking that is have all the doors open with the radio on and wiggle the wiring between the body and doors. If there's a break in it, you should be able to recreate the fault by doing that and then remove the fault the same way.