Volvo 740 electrical gremlin help

sandeman1sandeman1 Member Posts: 1
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???


  • vicenacvicenac Member Posts: 229
    Maybe the brushes are worn out (too short) or there is some dirt on the belt.
  • fred43fred43 Member Posts: 1
    I have a 1991 740 volvo no turbo. I have spent over 3 thousand dollars on a problem no one can solve. I get a trouble code 123 Coolant temp. sensor signal. I have replaced the sensor 3 times. The car is running very rich causing many problems. I replaced the engine brain box and that did not help. Fred
  • topcat01topcat01 Member Posts: 1
    I have a 1990 740GLE Volvo with 143K on the odometer. Since 2003 I have changed the EGR valve once and, EGR Vacuum Control solenoid three times. My check engine light is on now and still displaying the same old code of 154. My mechanic is questioning if my EGR temp sensor is bad or the ECU. Please share any knowledge on correcting this problem before it drives me over the edge.

  • mhydemhyde Member Posts: 1
    I just went thru (am going thru) something similar. First my car just cut out while driving one day. The mechanic said it was the battery (I thought it was the alternator). He replaced the battery, and two days later the car died while driving it. This time he said it was the alternator and replaced that. Two weeks later the battery (dash light) light was on along with the brake light, parking brake light and window washer fluid light. This time the mechanic said it was the alternator belt and replaced that. Now, two days later, the fuel gauge will only read full or empty and does so randomly when the car is started.
    Is it time to give up on this 1989 car?
  • walworthwalworth Member Posts: 1
    I want to ask if any one knows how to fix a sunroof problem my sunroof will not close and my door locks will not lock is it all part of the same siystem dose any one know how to fix tis problem
  • valadevalade Member Posts: 1
    Hi i have a 740 gl 1989,with only 147 000 km,anyways i cleaned out the motor with some product,i didnt spray it with water,and as soon as i started the car the check engine light came on,the light has been on for about 2 weeks and always stay's on,i also noticed that its taking up alot of gas. I also have an other problem,my right wheel in the front is sort of blocked,i can use the car,infact it goes well, but something is jammed in the brakes,and they are still good(70%),but it seems to skip,and i have no abs,when i turn on the right side,my wheels just spin for a while,its as if the car is forcing leading the back wheels to spin,anyways if anybody could give me some advice id really appreciate it alot,thx
  • 740_fan740_fan Member Posts: 2
    I think it is definitely the high time to change your mechanic in the first place, because he did a number of stupid things in his efforts to solve the problem (and if you paid him for all this, arrgh...).
    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.
  • hbasshbass Member Posts: 1
    I drive an 88 740gle. When I was driving 3 weeks ago, it suddenly cut off, no radio, power locks, power steering, and lights on the dash flashed. I had it towed to a volvo mechanic who had it for 3 weeks, did some work (checked alternator brushes, replaced ignition switch), and said they were unable to get it to malfunction. (It malfunctioned 4 times for me on the way home). It has since stopped working, it turns over, but won't kick to start, and when I put the key in the ignition, multiple lights on the dash light up. But still no power locks, radio, or or other things electrical. When it malfunctioned after picking it up from the mechanic, it did the same as noted in the beginning of this note. Any ideas?
  • kmeyerkmeyer Member Posts: 4
    Check to make sure the harmonic balancer is ok.
    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.
  • texholdem10000texholdem10000 Member Posts: 1
    I have a 1990 volvo 740 sw non turbo with 203,000 miles on it. The car runs great except for a stalling problem. It will stall anytime from an idle all the way up to highway speeds. On the highway just before it stalls it will lose throttle response it almost feels like the gas pedal has disconnected from the engine. Sometimes on the highway I can pump the gas and it will catch and continue to run other times it loses power and stalls about 10 or 15 seconds later. I called the dealer and they thought it was the internal fuel pump. It stalled 2 miles from the mechanic after they installed a new one with a new fuel filter. When it stalls you have to pump or floor the gas pedal to get it to restart. It will make a sound like no ignition or gas if you do not. It will start when it is cold without the gas pedal pumped or floored but not when it is hot. I can start it up in the morning and it will run for 10 to 20 miles before it stalls. But when it does it is very hard to start and keep running. Other than that it will run 60 70 80 90 100+ mile per hour and it runs great plenty of power no misses or backfires it just keeps stalling. Anyone ever seen a problem like this? thanks for any help you can give me.
  • littlelokelittleloke Member Posts: 2
    I have a 89 Volvo 740 GL. It has a factory Volvo security system integrated into it. When I purchased the vehicle a few years ago, it did not come with a remote for turning the alarm on and off. The factory stereo is also missing. I was fine with that. I didn't need an alarm or stereo.

    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.
  • caliberchiccaliberchic Member Posts: 402
    Is there a dedicated fuse for it in the fuse box? Pull the fuse if so.
  • littlelokelittleloke Member Posts: 2
    Sorry, no dedicated fuse. I should have mentioned this. I am no mechanic or electrician, but it seems as though the security system is wired into many of the systems. I pulled the fuse for the horn so that the horn would not keep going off while I was trying to figure things out, but the security circumvents that too and still makes the car beep! Doh!
  • horseexpresshorseexpress Member Posts: 1
    For the last six months or so I have noticed that my service light in my 1990 Volvo 740 GLE wagon comes on when I first start up the car and then it goes off after about five minutes of driving it. I am hoping that that is just a routine thing since it is an older car and it has over 224,000 miles on it, but could that actually mean that there is something wrong with it?
  • rstonerrstoner Member Posts: 1
    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?
  • rexcrexc Member Posts: 1
    i have an 89 wagon, it does about the same, thing it will run good for awhile and then start cuting out, back firing, to where i have to park it for several hours and it will run again for a while, i replaced plugs wires distrubter, still does it its driving me nuts, have you found the problem with yours? thanks rex
  • volvo740volvo740 Member Posts: 3
    Started car and the seatbelt, headlight, et whatever keeps beeping
    even as seatbelt on... headlights off, etc...

    Short of pulling fuse 9, not know what to do to muffle it..... cut wire?
  • snookman05snookman05 Member Posts: 2
    The oxygen sensor in your vehicle is what is causing the rich fueling problem. The brainbox (ECU) receives messages from the oxygen sensor and adjusts the the fuel mixture. The oxygen sensor is supposed to be good for the lifertime of the vehicle. It seems that something might have gone wrong wit it and it is sending back wrong info to the ECU which is causing the fuel nixture to cone out rich.
  • snookman05snookman05 Member Posts: 2
    My 1989 Volvo GL740 the speedoneter is working and I know it is an electrical speedoneter powered from the differential. I cannot find anything in chiltons on the odemeters. Are they supposed to work seperatly from the Speedometer? Are the speedometer and oddometers supposed to be one unit which are supposed to work together from the one connection from the differential? Are there supposed to be separate connections to the odometers and Speedometer? I have not taken ny dashboard instrument panel out to check and would and would like answers to my questions before I do. My odomete renains at the sane reading since i noticed this when I pushed the button to return the tripodoneter back to zero and it did not put any miles on it since that time and I would like both odometers to be operating again. Would appreciate some answers.
  • electricguyelectricguy Member Posts: 2
    My 740 (200,000 miles) was cutting out occasionally when you took your foot off the accelerator, so it would stall at intersections, when cornering slowly, even sometimes when coasting if you didn’t keep pumping the pedal. I had the problem for months and it got slowly worse, until the car in the end wouldn’t even hold idle when you started it. This is a hard problem to diagnose because the symptom looks like a fuel supply problem. It was actually due to a blocked sensor that reports no free oxygen in the manifold, the EMC computer is expecting at least some free oxygen so it cuts the gas supply down to lean out the mixture, but no oxygen is ever reported, so it cuts the gas so far down that it starves the engine. I fixed it by cleaning the oxygen sensor. It may have helped that I also replaced some broken capacitors in the EMC computer.

    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.
  • volvo740volvo740 Member Posts: 3
    I have replaced my odometer twice in 350k miles.. or is it 400k?

    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.
  • electricguyelectricguy Member Posts: 2
    I was able to fix a similar problem on my 740, please see post #21. If you do still have the problem, it's not much work to clean the oxygen sensor.
  • jamis18413jamis18413 Member Posts: 1
    this 740 stalls out once in a while. we have tried to narrow down what makes this happen and came up with "whenever we go up a hill of some kind and then have a light to stop at at the bottom of the hill or top is when it seems to want to stall." Right after it stalls it's hard to get it to start up...takes a few tries. I thought it was an ignition problem but I tug on the keys and ignition area when it runs and it does not stall. I am thinking it's the fuel filter clogging up. I have had someone tell me it could be the head gasket???? Not sure if that makes sense or not. Any ideas out there or has anyone seen anything similar? thanks.
  • brians_jabbrians_jab Member Posts: 1
    Electricguy, My son just bought a 1990 740GL wagon (4cyl, auto, non-turbo) and it is doing exactly the same thing you described. Unfortunately, after reading your posting we were unable to locate the "oxygen sensor" that you described so I would like to ask you for additional information. (1) What year is your 740? (2) Is it a 4cyl, non-turbo? (3) Is the "oxygen sensor" located in the exhaust or intake manifold? (4) Could you send a picture? I did some on-line searching for the "oxygen sensor" and it shows a tubular metal component that is attached in the exhaust system with a 19mm nut just before the catalytic convertor. This does not match your description, so I am thinking the component you are referring to must be something else. I appreciate your help.
  • richsrichs Member Posts: 3
    Try checking you master fuse box... #1 . It is in the consul. If I can recall.. Mine was , over the time starting to arc! Causing a poor connection. The main runs the main power AND the pump. Solved at first by using an electic grease... hope this helps.
  • arthur745arthur745 Member Posts: 4
    Be sure they are replacing the correct coolant temperature sensor. There are two. One is connected to the dash temperature guage; the other one, up under the exhaust manifold is connected to the computer under the dash. My 240 gave me exactly the same problem and left me stuck numerous times until my mechanic and I figured it out. And yes, we swapped computer modules, idle control motors, you name it.
  • arthur745arthur745 Member Posts: 4
    Also check the fuel pump and fuel system relays. They can arc also and cause all kinds of grief. Easy swap. Pick up a few spares on Ebay or CL and keep them in the console. Also download a relay diagram - just google it. I keep mine in the glovebox, which, by the way, has never seen a glove.
  • sallies2sallies2 Member Posts: 2
    Car won't start, acts like not getting gas. Fuel pump ok, lines ok, fuel injectors ok, fuel relay ok. No charge getting to the injectors. Still doing the exact same thing, "wants to" start but acting like no gas getting to it. Yes, it has gas in the tank. What else can we look for?
  • sivlvervolvo91sivlvervolvo91 Member Posts: 3
    I have a 1991 volvo 740. I have owned it for 3 years and it has run great until now. Its not starting. I have had this problem for a while and would happen about once every six months but after 10 minutes or so it would start, but now its not starting at all. I have changed the spark plugs and wires, replaced the fuel pump. about a month ago its been doin it a lot lately but have got it to start using starting fluid but now it just wont start. Once it does start it stays running and doesnt die or have any problems. Any ideas? I have done a little research and could it possibly be the crankshaft position sensor? if so where is that located?
  • sallies2sallies2 Member Posts: 2
    I went thru all that too. Ended up that the problem was the little spot right where the injectors spark. Got that cleaned and it's been fine ever since.
  • sivlvervolvo91sivlvervolvo91 Member Posts: 3
    so where the electrical connects are on the injectors?
  • mondobachmondobach Member Posts: 2
    Hello, I'm having the same sort of issues with my 1990 740GLE wagon. I have just had both fuel pumps replaced but still seem to be having the same issue. Did you ever get a response or find a resolution to this issue? I'd appreciate any help you can give me!
  • mondobachmondobach Member Posts: 2
    I'm hoping someone out there might be able to offer some help. I have a 1990 740 GLE wagon which I bought with about 91K miles on it a few years ago. It has intermittently had acceleration issues which have now worsened. I noticed that when I let the gas tank run down to about 1/4 I could hear the fuel pump under the drivers seat working erratically. As I result I always tried to keep the tank at least half full.

    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!
  • bydebyde Member Posts: 1
    I have a 1990 Volvo wagon 740 base. I left work car started fine stooped at gas station and come out and go to start car and nothing power but nothing happening at starter power going to starter but nothing anyone have any ideas this is my only car and have a trip planed in couple weeks. Thanks
  • hlcynikhlcynik Member Posts: 1
    Mondobach, this is just a hunch but have you tried replacing the fuel pump relay/crank position sensor?
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