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740 Electrical problems

daniels740

daniels740

Member
Joined
May 8, 2019
Location
South Florida
My '89 740 Turbo has been suffering an electrical issue that I want to get fixed this oncoming year.

What happens is: Randomly, when I am driving the car, most the electrics just cut out. The headlights no longer work, just interior lighting, high beams, and turn signals work, the SRS light comes on, and the fan blower motor gives out as well.

Also, the radio DOES keep working, unless you switch the blower motor to the second fan setting or higher (which doesn't work), then the radio shuts off.

Then, everything goes back to normal in an instant, randomly, the SRS light turns off, and everything else returns back to normal.

Any help is appreciated. Thanks.
 
c1800 said:
Check fuses, rotate or unplug/plug in their holders. Also check grounds, battery cable connections.
Click to expand...

Sorry for the late replay, I have a lot going on.

So, no blown fuses or bad contacts, and I checked and wiggled around the main ground points that I know of (fenders, driver's and passenger's kick panels.) I did NOT unscrew/tighten them or anything after seeing that wiggling them around did not make a difference.
 
Cleaned and tightened the grounds (both fenders, both kick panels) and no difference. It's really starting to aggravate me. Something I forgot to mention was that everything works fine when the key is at the II position and the car is not started.
 
You may have the ignition switch trying to fail. Most times it shows up after starting and the radio doesn’t come on or the blower isn’t on but they were operating when you shut it off. When this happens just jiggle the key. If everything comes on that shows the electrical part of the switch is failing. I guess this could happen while driving but I have not experienced it.
 
I add a second vote for checking the ignition switch. In my particular case, my 1987 745 T would frequently lose power (including the engine briefly cutting out) when I hit a particular bump in the road on the commute home. New switch fixed the problem. If you can find the Beck Arnley replacement they are around $50, otherwise they are in the $100 - $200 range depending on the brand.

With the key in the run position, wiggle the key just a little. This will frequently trigger the failure.
 
2 old for this said:
You may have the ignition switch trying to fail. Most times it shows up after starting and the radio doesn?t come on or the blower isn?t on but they were operating when you shut it off. When this happens just jiggle the key. If everything comes on that shows the electrical part of the switch is failing. I guess this could happen while driving but I have not experienced it.
Click to expand...

I saw another thread where this was the case, so I tried jiggling the key, to no avail. This makes me think it's not the ignition switch but I guess I can't be 100% sure.
 
142 guy said:
If you can find the Beck Arnley replacement they are around $50, otherwise they are in the $100 - $200 range depending on the brand.
Click to expand...
My first replacement ($70 Beck Arnley, Korea) lasted 9 months.
The second ($70 Beck Arnley, Korea) lasted 3 months.
The third ($120 "OEA", Czech Republic) is at 4-1/2 years and counting.

Just saying....
 
I had a similar problem on my '88 740. There are two power wires that tie in at the positive battery terminal and one was coming lose and was very corroded. If I remember correctly, one sent power to the starter and the other was for interior accessories.
 
I fiddled around the key a bit more, and to my surprise, the issue would go away as I held the key to the right just a bit. This was after I sanded and tightened my grounds to find that it didn't make a difference.

So, what brand ignition switch do you guys recommend for longevity and reliability?
 
It has been 20 years since I replaced mine and the car has since moved on to other owners. The replacement was whatever the local auto parts supplier had in stock - might have been Intermotor and who knows where their parts come from.

As I recall, the cover on the switch is retained by 4 bent metal tabs. I think by bending the tabs back you can pop the cover revealing the switch contacts. In some cases the switch can be rehabilitated by simple cleaning of the electrical contacts. Other times, a little bending of the contact to increase pressure on a contact can resolve the problem. Pulling the switch apart may also reveal that the contacts are burnt or really pitted or otherwise complete toast requiring a new switch. I rehabbed a 140 switch which was a bit harder because the cover was retained by rivets which had to be drilled out. If you pull it a part, do so slowly and over a box because sometimes there are spring loaded parts which can go flying, in which case a new switch may become a self fulfilling prophecy.
 
I was just about to say that the Intermotor part was NLA, when I found it on Rockauto for $95. Pretty steep, but the next best thing was the $53 Beck/Arnley switch that "MasterBlaster" said only lasted under a year.

Then I thought, would it be a better decision to get the Genuine Volvo Ignition Switch for ~$30 more than the Intermotor if it meant a lifetime warranty as well as superior quality from FCP Euro?
 
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