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Car Forum / Volvo Cars / February 20061990 740GL, electrical strangeness
After driving to a fish pond on a rough, bumpy dirt road, my 1990 740 started doing some strange things. When I turned on the headlights, the wipers come on. I had to pull the horn/wiper fuse to get home without the wipers screeching on the dry windshield. The next day, I noticed that the power windows were dead, but the fuse looks good (I don't have a 30A handy to actually switch it out and test it). Next, the turn signals went out, and the fuse is blown. However, when I put in a new fuse, it blows immediately. Obviously, something electical is wrong. A short somewhere perhaps? How is something like this diagnosed by the home mechanic? Thanks, Jay R. > After driving to a fish pond on a rough, bumpy dirt road, my 1990 740 > started doing some strange things. On the inside of each wing (on my UK spec 740, at least) is a bunch of earth (ground) terminals. I'd start by checking all of them as 740s seem to have real problems with earthing. Check the engine earth strap too (attached to the bulkhead). It seems that it was made a little too short - mine had snapped. Si > On the inside of each wing (on my UK spec 740, at least) is a bunch of earth > (ground) terminals. I'd start by checking all of them as 740s seem to have > real problems with earthing. Check the engine earth strap too (attached to > the bulkhead). It seems that it was made a little too short - mine had > snapped. Sounds good, I'll check. Er, what's the USA word for what is called a "wing" in the UK? Fender. Boot is Trunk, Bonnet is Hood, estate is wagon, saloon is sedan, Sills are Rocker Panels, manifolds are headers. I may be wrong about Fender, but it is the word that sprang to mind. All the best, Peter. 700/900/90 Register Keeper, Volvo Owners Club (UK). >> On the inside of each wing (on my UK spec 740, at least) is a bunch of >> earth (ground) terminals. I'd start by checking all of them as 740s seem [quoted text clipped - 4 lines] > Sounds good, I'll check. Er, what's the USA word for what is called a > "wing" in the UK? fender >> On the inside of each wing (on my UK spec 740, at least) is a bunch of >> earth (ground) terminals. I'd start by checking all of them as 740s [quoted text clipped - 4 lines] > Sounds good, I'll check. Er, what's the USA word for what is called a > "wing" in the UK? Fender >> On the inside of each wing (on my UK spec 740, at least) is a bunch >> of earth (ground) terminals. I'd start by checking all of them as [quoted text clipped - 4 lines] > Sounds good, I'll check. Er, what's the USA word for what is called a > "wing" in the UK? Heh! Fenders, as others have said. I imagine that our continued use of the word "wing" originated from early cars where the fenders did look a little like wings... http://www.classiccarshop.co.uk/Cars/bentley_mk_v.htm Si I have just gone through the same deal with my 90 wagon. After going to all the forums I could and getting the ground is bad answer. I finally tore into it with a vengeance. If this hasn't been repaired yet you will need to take out the glove box and the kick panel on the passengers side. You will find a cluster of red wires all hooked into a buss bar by spade connectors. this will be covered by a plastic cover which may show signs of melting from the heat generated by a poor connection. Hey Volvo fire the bum who came up with this little fire starter!! Once you find it their are 2 ways of fixing it . You can cut off all the spade connectors and twist and solder , wire nut and electrical tape the whole wad, or you may chose to solder the spades onto the buss bar as I did. Either way that took care of most of my electrical spooks. You can do it now or you can do it later but you Will be doing it sometime as this set up causes a lot of grief to Volvo owners. Mine caused the car to quit while in traffic and wouldn't start until days later at my garage when this mess was found. And oh ya I checked all the ground stuff twice!! Good Luck Mac > >> On the inside of each wing (on my UK spec 740, at least) is a bunch > >> of earth (ground) terminals. I'd start by checking all of them as [quoted text clipped - 11 lines] > > Si Mac, This sounds great, I will definitely make this a project. Regarding my 740, I checked the grounding harnesses inside each fender. There were two on the passenger side, and one on the driver's side. They did not look corroded and were properly affixed. I didn't see any wires that appeared to have come unclipped from either fender ground. I did find one more clue to my problem. I noticed that my driver's side headlight is extremely dim. When I turn on the left turn signal, both the driver's side headlight and the flasher blink weakly. The passenger side light is fine. So right now the turn signals are working again (new fuse that didn't blow immediately this time) and the power windows have resumed working, mysteriously. However, I still have the dim headlight and the wipers still come on when I turn on my headlights. So something's still not right and I need to get it fixed, but I am driving the car. JayR. > I have just gone through the same deal with my 90 wagon. > After going to all the forums I could and getting the ground is bad [quoted text clipped - 18 lines] > Good Luck > Mac > Mac, > [quoted text clipped - 17 lines] > > JayR. Whenever you have dim lights, and switches from one device affecting another, then I always suspect grounds. Keep in mind the problem can be anywhere on the ground wire from the connection at the device to the connection on the body.  SignatureMike F. Thornhill (near Toronto), Ont. Replace tt with t (twice!) and remove parentheses to email me directly. (But I check the newsgroup more often than this email address.) > Whenever you have dim lights, and switches from one device affecting > another, then I always suspect grounds. Keep in mind the problem can be > anywhere on the ground wire from the connection at the device to the > connection on the body. Ok, then it's pretty certain I've got a grounding issue. If I've already looked in the obvious places and don't see bad connection, is there a way to locate a bad ground, like a tool of some kind? JR > > Whenever you have dim lights, and switches from one device affecting > > another, then I always suspect grounds. Keep in mind the problem can be [quoted text clipped - 6 lines] > > JR One tool that is necessary would be a voltmeter. Put one lead on the negative battery terminal. Measure the voltage at the ground wire at the headlight. It should be close to zero, I'd say maximum about 0.3 V. Another tool that would be very helpful is a wiring diagrams manual, so you know which colour wires are supposed to do what. Because your wipers are turning on, I ask the question, what are your windshield washers doing during all this? SignatureMike F. Thornhill (near Toronto), Ont. Replace tt with t (twice!) and remove parentheses to email me directly. (But I check the newsgroup more often than this email address.) > Because your wipers are turning on, I ask the question, what are your > windshield washers doing during all this? Washers are inactive -- it seems to be affecting only the wiper motor. > > Because your wipers are turning on, I ask the question, what are your > > windshield washers doing during all this? > > Washers are inactive -- it seems to be affecting only the wiper motor. What turns the wipers on other than the wiper switch? The washer pump. Energizing the washer pump fires up the wiper motor, so if your headlight is being grounded through the washer pump, then the wiper relay will be receiving a signal down that wire, and will turn the wipers on. Try disconnecting the wires at the washer pump. SignatureMike F. Thornhill (near Toronto), Ont. Replace tt with t (twice!) and remove parentheses to email me directly. (But I check the newsgroup more often than this email address.) Rather than just rely on my visual inspection, I decided to follow the advice here and disconnect/clean/reconnect the ground wires inside the fenders. Vallah! Problem gone. I still don't really understand why my #8 fuse (turn signals) was blowing immediatly upon insertion, but everything's back to normal now. Thanks to all who responded! mudguard fender wing bulk head fire wall boot trunk bonnet hood gear stick gear lever auto car gas petrol >>> On the inside of each wing (on my UK spec 740, at least) is a bunch >>> of earth (ground) terminals. I'd start by checking all of them as [quoted text clipped - 11 lines] > > Si |
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