Hello Everybody,
I have a 1990 Volvo 740GL. It is very reliable mechanically, but has some electrical problems:
Fuel gauge usually does not work. When I turn on electricity with the ignition key, the fuel gauge needle turns right, but suddenly falls back near to zero. When I turn off electricity and turn on again, the needle turns right again, but not as much as previous time, and falls back. At the third time the needle hardly moves. What could it be?
Speedometer also does not work. Simply does nothing. I checked already the dashboard, but it seems for me OK. No bad wire, connectors are tight. I checked the connector at speed sensor under the car. I put some WD40 in it, but nothing happened.
Thanks God, the clock, the RPM gauge and the temp gauge works fine.
Sometimes, when I make longer trips, sometimes the speedometer and the fuel gauge begins to work (as I could see they start working together). When I stop the engine and start it again, usually they don't do anything again.
Another big problem of mine is the alarm system. I have a MOSS 740 security system. It has a little remote control with one button. It handles some movement sensors and the central lock. I have realized that the security system consumes about 80 milliAmps! It discharges my accumulator less than three weeks. So now, when I stop the car, I disconnect the accumulator to prevent it from discharge. It works, but not too elegant. Any idea, whats happening in that machine? Sometimes I have the feeling that maybe the alarm system makes something with the speedometer and the fuel gauge also. Is this possible?
Another smaller problem: the red lamp in the right front door does not lights, when I open that door. I have realized that it begins to light, when I open the right second door! Can anybody help me, what should I re-bind to connect that lamp to the swith at the front door?
Thank you any help in advance,
Tamas
740 GL speedometer and other small errors
-
wojeepster
- Posts: 259
- Joined: 15 November 2005
- Year and Model:
- Location: Hendersonville, NC
The only thing that is common to both gages is the ground. So I would check the ground for those two gages.
Hello,
Tamas
Where is the ground of temp and RPM? Are those grounds common with speed and fuel grounds? Because RPM and temp works fine. And where can I find this ground point?wojeepster wrote:The only thing that is common to both gages is the ground. So I would check the ground for those two gages.
Tamas
Hello Everybody again,
Unfortunately, I still could not solve the problem of my speedometer and fuel gauge, but I solved the problem of my door lights:
SYMPTOMS: when the passenger side front door was opened, the red door light did not work. When the passenger side back door was also opened, the red light in the opened front door began to work.
CAUSE: wrong door switch at the front door. The door switch has three pins:
- One is coming from a relay of the red lamp or something like that,
- one is the ground,
- one is a sense pin (sensing opened door for the cabin light and for the relay).
When the door is opened, both the relay pin and the sense pin must be grounded by the switch. If the electrodes in the switch are oxidized causing bad contacts, mystical things can happen with the door light.
SOLUTION:
- Take out bad switch with a torque screwdriver.
- repair switch (or replace it, if you have a lot of money). The switch can be opened by pushing in the two plastic clips on the switch by a screwdriver. The oxidized electrodes can be cleaned by polishing paper.
I will go on with the speedometer.
Unfortunately, I still could not solve the problem of my speedometer and fuel gauge, but I solved the problem of my door lights:
SYMPTOMS: when the passenger side front door was opened, the red door light did not work. When the passenger side back door was also opened, the red light in the opened front door began to work.
CAUSE: wrong door switch at the front door. The door switch has three pins:
- One is coming from a relay of the red lamp or something like that,
- one is the ground,
- one is a sense pin (sensing opened door for the cabin light and for the relay).
When the door is opened, both the relay pin and the sense pin must be grounded by the switch. If the electrodes in the switch are oxidized causing bad contacts, mystical things can happen with the door light.
SOLUTION:
- Take out bad switch with a torque screwdriver.
- repair switch (or replace it, if you have a lot of money). The switch can be opened by pushing in the two plastic clips on the switch by a screwdriver. The oxidized electrodes can be cleaned by polishing paper.
I will go on with the speedometer.
I agree that it sounds like a bad ground. The ground for the whole console has it s connection behind a panel in the right footwell. It is placed behind the panel just in front of the right front door. There you will find a ground bar, I have had some problems with that connection.
Hello,
By the way, last day I measured the resistance at the small 4 pin connector on the back of the dashboard, between the blue and brown wires. I read that these wires are going to the speed sensor. When the ignition key was in position I, the resistance was 1.5 kOhm. However, when I turned the key to position II, the resistance became infinity. Is it OK? I think it's not...
Tamas
Thank you for the advise. So the ground bar is not around the dashboard but somewhere around the glove box? Shall I remove somehow the plastic part above the glove box? Could you tell me, how?LaRy wrote:... The ground for the whole console has it s connection behind a panel in the right footwell. It is placed behind the panel just in front of the right front door...
By the way, last day I measured the resistance at the small 4 pin connector on the back of the dashboard, between the blue and brown wires. I read that these wires are going to the speed sensor. When the ignition key was in position I, the resistance was 1.5 kOhm. However, when I turned the key to position II, the resistance became infinity. Is it OK? I think it's not...
Tamas
To reach the ground bar you have to remove the plastic panel under the glove box. Some plastic screws should be twisted 90 degrees, then you just slide the panel out . Then you loosen the two long screews you can find at the plastic panel in front of the door. You also have to release the plastic cover at the doorstep, at least the screw in front.
About the speed sensor, it is always difficult to make messurments on inductive sensors. The only reliable way is to have a frequency meter and see if you get some frequenzy out from the sensor while driving.
About the speed sensor, it is always difficult to make messurments on inductive sensors. The only reliable way is to have a frequency meter and see if you get some frequenzy out from the sensor while driving.
Hello LaRy,
thank you for the advice about the right footwell ground bar. I have checked it, and not just that one, but the other one in the left footwell. Both of them is clean, rustless and connectors are tight, so the error is not here
.
I am sure that this failure is a contact failure, because during driving, at big bumps, the speedometer suddenly begins (or stops) to work. And now I can see that this is independent from the fuel gauge.
Is there any connection point between the speed sensor differential connector and the four pin connector behind the dashboard (grounding of the wires, extra connectors etc.)?
Anyway, thanks again for the plastic removal tip, because, when I removed the plastic part from the ground bar, I have found a lot of dried leaves in the ventilation hole. I removed them and now the whining noise from the ventilation disappeared
Tamas
thank you for the advice about the right footwell ground bar. I have checked it, and not just that one, but the other one in the left footwell. Both of them is clean, rustless and connectors are tight, so the error is not here
. I am sure that this failure is a contact failure, because during driving, at big bumps, the speedometer suddenly begins (or stops) to work. And now I can see that this is independent from the fuel gauge.
Is there any connection point between the speed sensor differential connector and the four pin connector behind the dashboard (grounding of the wires, extra connectors etc.)?
Anyway, thanks again for the plastic removal tip, because, when I removed the plastic part from the ground bar, I have found a lot of dried leaves in the ventilation hole. I removed them and now the whining noise from the ventilation disappeared
Tamas
Have you tried to hit the dashboard rather hard from upper side when driving? It is rather common that it will make the speedometer to work. If it helps the fault could be caused by some small electronic circuit in the speedometer. I had to change the speedometer once to an used one with this 6 - 8 legged component changed. The expert told me that this little black thing got very small cracks when ageing and that was causing the problem. So he used to change the component, test the speedometer and sell it again.
Personally I don't like the quality of the connectors to the consol. It could of course also be bad connection. Could be a good idea to scratch the connections points with a sharp knife so you get fresh cupper visiable.
Personally I don't like the quality of the connectors to the consol. It could of course also be bad connection. Could be a good idea to scratch the connections points with a sharp knife so you get fresh cupper visiable.
Hello Everybody again,
I can proudly present that I repaired my fuel gauge and my speedometer
SYMPTOMS:
speedometer, tripometer, odometer and fuel gauge usually does not work. Very rarely they start to work correctly, but next start they died again. Other instruments are OK.
CAUSE:
- wrong contact at a big connector under the steering whel near to the A pillar,
- maybe wrong contact at the speed sensor at the differential,
- wrong instrument panel (possibly the PCB wiring and/or the electrolyte capacitors).
SOLUTION:
- check and clean the speed sensor connector at the differential,
(was not enough for me, nothing happened)
- check the grounding points: To reach the ground bar you have to remove the plastic panel under the glove box. Some plastic screws should be twisted 90 degrees, then you just slide the panel out . Then you loosen the two long screews you can find at the plastic panel in front of the door. You also have to release the plastic cover at the doorstep, at least the screw in front. You can also check the grounding point at the left side, under the steering wheel.
(they were OK for me)
- check the connectors under the steering wheel. You have to remove the torque screws and the plastic cover under the steering wheel. You will find here some connectors. Check, if they are tight and clean the electrodes, if necessary.
(one was dirty, I cleaned with WD40 and suddenly the tripometer and the odometer started, but nothing more)
- check the connectors at the rear of the instrument panel. (You can take out the panel, if you remove the plastic cover pads at the clock knob and at the light knob with a thin screw-driver, remove the screws under the plastic pads and pull out the instrument panel).
(was OK for me)
- replace instruments. I could buy a used instrument panel in Germany for 10 Euro in a junk-yard, and it was fully functional. Suddenly everything started. I think that PCB wiring or contacts are broken in the old instrument panel and/or electrolyte capacitors are too old.
Tamas
I can proudly present that I repaired my fuel gauge and my speedometer
SYMPTOMS:
speedometer, tripometer, odometer and fuel gauge usually does not work. Very rarely they start to work correctly, but next start they died again. Other instruments are OK.
CAUSE:
- wrong contact at a big connector under the steering whel near to the A pillar,
- maybe wrong contact at the speed sensor at the differential,
- wrong instrument panel (possibly the PCB wiring and/or the electrolyte capacitors).
SOLUTION:
- check and clean the speed sensor connector at the differential,
(was not enough for me, nothing happened)
- check the grounding points: To reach the ground bar you have to remove the plastic panel under the glove box. Some plastic screws should be twisted 90 degrees, then you just slide the panel out . Then you loosen the two long screews you can find at the plastic panel in front of the door. You also have to release the plastic cover at the doorstep, at least the screw in front. You can also check the grounding point at the left side, under the steering wheel.
(they were OK for me)
- check the connectors under the steering wheel. You have to remove the torque screws and the plastic cover under the steering wheel. You will find here some connectors. Check, if they are tight and clean the electrodes, if necessary.
(one was dirty, I cleaned with WD40 and suddenly the tripometer and the odometer started, but nothing more)
- check the connectors at the rear of the instrument panel. (You can take out the panel, if you remove the plastic cover pads at the clock knob and at the light knob with a thin screw-driver, remove the screws under the plastic pads and pull out the instrument panel).
(was OK for me)
- replace instruments. I could buy a used instrument panel in Germany for 10 Euro in a junk-yard, and it was fully functional. Suddenly everything started. I think that PCB wiring or contacts are broken in the old instrument panel and/or electrolyte capacitors are too old.
Tamas
-
- Similar Topics
- Replies
- Views
- Last post