740 - weird electrical issue.

[redtel35]

Hi all,

I have a very strange thing going on in my recently acquired 1990 740 GL estate.

With key in ignition at position 1 and position 2, all electrics work fine. However, as soon as I switch to position 3 or start, I lose electrics to horn, radio, blower, wipers and electric mirrors. Everything else electrical still works and car starts fine.

I have tested for power at the fuses and there is power there, so can only assume that something happens between fuses and device.

Any help greatly appreciated.

Terry

[bob12]

I think that's normal. I will have to check!!

You are only in position lll for the engine start and the key returns automatically to 'll' when released and it's not like it's a long time or you need these auxiliaries for that short period of time. Either that or the main switch (replaceable) behind the lock is playing up.

Bob

[940volvoman]

Yeah, thats normal, mine does that too......

[aardvarkash10]

yup - pretty much a universal approach. Diverts supply from all non-essential devices so there is maximum battery available for cranking hte engine over.

[Laird Scooby]

What they've all said ^^^^^ perfectly normal and designed in.

[redtel35]

I think I may have confused things. The issue is that when the key springs back and the engine starts, power to the electrics doesn't return.

Does that make sense?

Many Thanks

[redtel35]

Hi all,

Thanks for the quick replies and it seems as though the switch is definitely the issue.

I've already got the instrument cluster out as I've got to replace a couple of gauges.

The lower panel is also off as I had to trace some ropey fog light wiring.

Thanks for the help!

[Laird Scooby]

Originally Posted by redtel35

Hi all,

Thanks for the quick replies and it seems as though the switch is definitely the issue.

I've already got the instrument cluster out as I've got to replace a couple of gauges.

The lower panel is also off as I had to trace some ropey fog light wiring.

Thanks for the help!

You should be able to see the switch fairly easily, if you take the two screws out you should be able to pull it out far enough to either take a photo of the part number or see it easily enough to write it down. THen you should be able to get one from Volvo.

Out of interest, if you turn the key back manually to position 2 after starting, is power restored to the circuits that are cut during starting?

Also which gauges are you renewing?

[bob12]

I have found that the electrical part of the switch gear is very robust. Bob

[redtel35]

I need to replace the fuel gauge and the coolant gauge. I have managed to source the correct VDO replacements. I also need to replace the cog on the speedo as that has several teeth missing and so odometer has stopped working.