Volvo 740 electrical gremlin help
Here's a strange one that maybe someone has seen before:
A 1988 740 GLE with 190K miles. The alternator tests good (charging the battery), and just put in a new battery.
Indications: Above 2000 rpm, the idiot lights on the dash come on just as if there was a alternator problem. Below 1000 rpm the lights come on very very dim. Between 1000 and 2000 rpms the lights stay off.
Any ideas???
A 1988 740 GLE with 190K miles. The alternator tests good (charging the battery), and just put in a new battery.
Indications: Above 2000 rpm, the idiot lights on the dash come on just as if there was a alternator problem. Below 1000 rpm the lights come on very very dim. Between 1000 and 2000 rpms the lights stay off.
Any ideas???
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tc
Is it time to give up on this 1989 car?
It is difficult to judge anything without seeing the car, but from your description it is clear that:
1. The car cut out because the battery was empty (which was not the reason to install a new battery immediately).
2. The car died while driving it after two days, with new battery - not knowing how exactly the car was used during these two days is very difficult to judge or assume anything, but the least mistake may be made if saying that the new battery also went empty > there possibly is a problem with the alternator (but maybe not (only) the alternator, or, better to say when alternator is not charging, this does not mean that it is not good, there are other part of installation which may produce problems causing a good alternator not to work properly)
3. Mechanic said it is the problem with the alternator and he replaced it > he should have said what exactly was the problem with the alternator, it is not so difficult to understand. You never replace an alternator if you are not sure that it must be replaced, and you must know why it needs to be replaced. So far we do not know why the alternator was replaced, and what is more important, was it properly replaced (although that should be the most simple thing to do for any mechanic).
4. Dashboard lights, conclusion that there is a problem with the alternator belt > if there really was a problem with the alternator belt, such a problem should never occur only two weeks after replacement of an alternator, because: you inspect the old belt and do not use it unless it is really good, and you know how to install it (tension-wise) properly, being it old or new, so that in two weeks no problem with it should occur.
5. I assume that now everything works except the fuel gauge > this is a common problem with 740 dashboards, and can be caused by worn instrument which tends not to move from 0, especially when a tank is pretty empty, so the force needed to move the needle not too much from zero is small anyway (usually it is put in working condition with a solid tap of your hand on the dashboard above it), sometimes - when you fill the tank completely and the needle of an instrument gets stuck on the maximum you sort out this problem in the same way as explain above. If it goes erratically or stays at different positions abnormally during normal use of the car (car in move, not only engine working), problem may be caused by the worn rheostat in petrol tank, which produces signal for the petrol gauge. problem may also be caused by poor/corroded contacts at number of places.
6. It would be good to know whether, when the problem with signal lamps on the dashboard was spotted, was also any other problem present at the same time (for example with outside lights, cabin light, radio, etc). This problem (dashboard lights only) may be caused by the poor contacts on the instrument panel or somewhere else (fuse box, for example)
7. Very simple check-up of the alternator: when the engine is on and idling (best results immediately after starting a cold engine, and better in winter than in summer, but in general at any time), turn on at the same time both the headlamps and the fan switch to maximum (! not the airco, only the fan) and it must be noticeable that the number of revolution of the engine drops - you should hear this and you should see this on the rpm meter, if there is one. When you turn off lights and fan, again simultaneously, the engine speed must increase a little bit. Why lights/fan, and why after starting - because then you are using approximately 120 Watts which must be compensated/produced by a good alternator, and in order to produce the electricity, the alternator produces strong magnetic field and increases the overall resistance that the crankshaft is having at that moment, which is always anyway the biggest immediately after starting the engine (cold oil), and greater in winter (even colder oil, everything more stiff/rotating parts of an engine more close together, etc). If the battery is very bad, then you will have this effect more noticeable - which can be seen, for example when somebody is providing jumpstart to a car with a dead battery - if a car with good battery has engine idling, connecting the jumpstart cables to a car with dead battery will produce slowing down the engine of the car used for jumpstart, this can also be a good way to damage your alternator, or engine may stall - that's why people always press the accelerator pedal when the other engine is started, because at this moment we have: a) dead battery taking the power from a good battery, which must be additionally charged by the alternator (which may not be designed for such load...) and b) we have additional big need for electricity i.e. power for the starter motor of the dead car -... here I will stop.
8. A wire which provides the incitement for the alternator tends to cause problems in certain situations as well - if it is a car with an alternator below the exhaust manifold, and if the alternator was improperly maintained, replaced, whatever, and this wire left too close to the exhaust manifold, it tends to loose its characteristics - and must be replaced although it may look usable - you suspect on this if the wire is too stiff, or if the isolation is desintegrating at certain parts of it.
9. Described test of the alternator should be done after we know that the belt is properly tensioned, i.e. if it is suspected that the alternator is not working properly, first check the belt, then the alternator / other parts of the electrical installation PRIOR to removing the alternator.
Don't give up, I drive a 1989 740 with 615.000 km on it and have had no special problems in four years that I own it
Regards from Den Haag, The Netherlands.
The rubber seal between the two halves can wear out.
The the result is that the belt driven devices can turn slower or at times stop turning while the engine is still running fine.
I checked this by putting a white line from the inside of the balancer to the outer edge, then ran the engine while turning the steering wheel. When I shut the engine off and checked, the lines were no longer aligned.
This caused my battery to drain and the dash "idiot" lights to come on at various times, the worst being at idle while turning the steering wheel.
I recently replaced the battery and once I did, the security system reset and is now on. I do not know how to shut it off and can't operate the vehicle while it is activated. I talked with my local dealership service department and tried locking the vehicle twice and unlocking it twice (didn't work). He told me that the stereo had a security system interface on it and that might be part of the problem (since mine is missing).
Is there something I can do to manually shut off the alarm or disable it? I would be more than happy to not have to deal with the security system ever again. Upon looking at the power to the security, it appears that I cannot simply disconnect it from the power without also disconnecting many other systems.
Thanks in advance for any ideas you suggest.
After running dry our '88 740 has recieved a new relay, pump (regency style) and filter but to no avail. No power to the pump, is there a shut off switch for this somewhere I need to reset?
thanks
even as seatbelt on... headlights off, etc...
Short of pulling fuse 9, not know what to do to muffle it..... cut wire?
I disconnected the battery before doing any of the electrical work. The oxygen sensor on my 740 is a 3-wire type (positive, ground, and sensor) very low down on the manifold, right up against the firewall. I was nervous about damaging it but it’s really tough, just a smooth rubber cylindrical plug with a small metal tip, slides up and out easily once you’ve undone the single retaining screw (there’s almost no room to work, you’ll need a 10mm extended socket and ratchet, but you don’t need the special Volvo tool described in the manual). I did follow the electrical test procedure in the manual. Even though the sensor checked out fine electrically, it wasn’t working because the tip was almost completely gummed up with soot. It cleaned up fine with rubbing alcohol and a very light sandpapering.
I also fixed the EMC because the workshop diagnostics said there was an electrical problem, but if I were doing it again I’d clean the oxygen sensor first and then road-test the car before doing any more work. Check the maker/serial on the EMC, I had a 940 Bendix EMC in a 740 saloon, so you might need the 940 workshop manual to check your electrics. The EMC computer is the size of a paper-back book and is behind the plastic wall to the right of the front passenger’s feet. I had to break a coupla glue seals to get to the circuit board once I had taken the EMC computer out of its aluminum case. I used a cheap Radio Shack tester to check the capacitors on the circuit board (caps do age with time, one even broke apart in my hand) and replaced three of them by soldering each new capacitor to the cut-off leads of the old one. The EMC computer is old-fashioned with mostly big parts, so doesn’t require much soldering skill. Caps have polarity, so they must be soldered on the right way round (the short lead and the light-gray stripe mark the negative lead, the one that goes where the circuit board says “-ive”).
I’m not a mechanic. I was so fed up with the car, if I could have found a decent recon EMC I’d have happily (well, fairly happily) paid $200 for it. But the caps cost me less than $5 for all three, and took less than an hour to fit, so I came out feeling good. The car runs so well now it reminds me of why I bought it in the first place.
When it stops your car has less mileage. Hence car is worth more
at trade in time. Not a factor in 25 year old cars. Big cities have shops that
repair them in a few hours. It seems to be a specialized job and cheaper
than buyin a new one.
While driving to get gas one night at about 30-40 MPH the car suddenly had no power...someone else in a post here stated the same problem by saying it was as if the accelerator had been suddenly disconnected. I rolled to the side of the road when it finally stalled. However, it immediately started up again and I was able to get to the gas station, fill up, and get home without further problem.
This same thing has now happened a few times even with a 3/4 to full tank. My mechanic replaced both fuel pumps but I am still having the problem.
The car will also sometimes not start. Usually when I turn the key to "on" I can hear the fuel pump activate. However, I have noticed that on the occasions that it doesn't start, I cannot hear the pump come on. I turn the key on and off a few times until I hear the pump activate and then it turns over just fine.
So, my question is, what might it be that is not telling the fuel pump to come on when the car is started and could this same thing also be telling the pump to quit while the car is moving?
I would greatly appreciate any guidance that anyone might be able to give to me!