740 - weird electrical issue.
 

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

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 :)

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

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

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

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

In that case there are one of three things causing it.

1. The switch is worn

2. The switch is loose

3. There is a broken wire on the back of the switch.

The only way of finding out is to remove the underdash trim on the drivers side and use a mirror and a torch to see if it's loose or has a broken wire. If it's neither, you will either have to take the registration number to your local Volvo dealer and order a starter switch (as that's what Volvo call them) from the reg number or remove the switch (2 screws and an electrical plug), get the part number and order from that.

There are (from memory) 4 different starter switches fitted to the 7xx and they are NOT interchangeable - you MUST get the correct one!

Don't be tempted by the cheap switches on ebay, only two of them are compatible with two of the possible Volvo switches, Sods Law is (like the one i had) you will have a different one. Also they're not brilliant quality so could leave you in the same position in a year or two! :speechless-smiley-5

You may find it easier to remove the instrument cluster surround and the instrument cluster for access to the switch, your choice. That was how i did it on my last 740GLE when i had to renew the starter switch. :thumbs_up:

sounds like the contact inside the electrical section of the ignition switch are worn, YEs you can just replace the electrical bit, comes complete with a short wiring harness which connects to the main dash harness at the side of the column with a multi plug. breakers a good place to start as they don't fail that often. :)

Sorry but i have to disagree strongly on your last statement. First, any switch for a 740 will be at least 30 years old by now, second, there's no way to guarantee how it's been treated or predict how long it will last, third, most breakers are online now so getting the right switch could be tricky, fourth - why gamble with a used part like that?

Also they do fail fairly regularly, they're probably the most used switch in the car! On almost every journey, the switch will be operated at least twice, once on the way there and again on the way back, never mind stopping for fuel, switching off due to being stuck in traffic and so on.

You've described how to do it which suggests you've had to do it as well, that's two of us out of the people who have answered so far - time will tell if others have but i'm fairly sure there will be one or two more people out of those who have responded to this thread.
It's a straw poll but makes almost all of us! :eek::speechless-smiley-5:eek:

when you have spent 35 years of your working career as an auto electrician, I guess yes, I have changed a few ignition switches, but tbh, not many on Volvo's, no wont mention any other brands on here, im not one to offend . :)