Volvo 740 1989 Electrical problem



My 1989 740 Volvo automatic wagon has a long term electrical problem. Once in awhile it will not start. Usually if I wait 1/2 hour, or sometimes overnight, it will start. Towing it to the repair shop will guarantee that it will start once there. Also, my mechanic has put an emergency wire attached directly to the starter, that has always started the car. It by passes the ignition and safety switch. But lately a second problem has evolve… with the emergency wire contacting the positive terminal of the battery, the car will crank, but sometimes won’t start. Again, if I wait until cool, the engine will start. The last time this happened I check for spark and did not see any, but went back and the car started up the next morning. thanks for any suggestions.


Your ignition switch may be at fault or the wiring to the ignition itself. You need to make sure power is getting to the ignition first when this trouble happens. If it is then you need to check the ignition sytem for a fault. I would recommend you get a service manual for the vehicle. It will be good to have on hand.


Thanks for your attention. The volvo mechanic has replaced the ignition switch. My understanding is that this could involve the starter, ignition, safety switch, relays and wiring. We’ve been trying to isolate the problem, but it has eluded us so far.


Your mechanic seems to be interested in changing parts to fix the problem. Sometimes, the coolant temperature sensor (which feeds the engine computer, not the temperature sender for the dash gage) will be causing this problem. $40 bucks cheap at Advance Auto Parts.


right after posting my 86 volvo problem i read your post- sounds identical–must be an epidemic. Hopefully someone will have answer for both of us.


Thanks for your reply regarding a possible coolant temperature sensor. I’ll check into that. Doug


My mechanic thinks we should try a new starter next. This sounds illogical (as he even says) since a wire from the starter directly to the battery will start the car. However, he says that he was experiencing the same problem and finally replaced the starter. That resolved the problem for him. The downside of this approach is that it will cost about $500. But I’ve been dealing with this for 5 years now. I’ll try this, and if that doesn’t do it I may have to scrap it. Doug


If you have a no-start and there is no starter solenoid click then that usually points to one of these:
Ignition switch-electrical, not key and tumbler. Which one did they replace?Inhibitor switch.
Junction terminal. This is between the battery and ignition switch and in-line on the battery positive cable. Corroded, maybe?

No spark means:
Bad ignition switch.
Faulty coil or module.
Fault in the ECM or wiring.
With no spark, the blue wire at the coil should be checked for 12 volts both in the START and RUN positions.
If power is not provided at this terminal then one has to wonder if the switch was really changed as a diagram does not show a connection between the two; only one continuous wire.


If you are saying that using a jumper wire between the starter solenoid ignition wire and battery makes the starter work when this trouble happens then replacing the starter is not going to help. This means that the solenoid is not getting voltage from the ignition switch for some reason. This is a simple problem to solve when the trouble is occuring. Using a test light to check for voltage is all you need to test with.

You can install a remote starter switch to make the starter run when this trouble occurs.


My 1990 760 wagon,refuses to start after drivng for a bit with the air conditioner turned on,in hot weather(Tucson).I can always start it after waiting 45to 60 minutes.There is no clicking sound ,and the car does not turn over.No one can fix.In desperation
I changed a relay (K) and it appeared to be the fix.Then after 6 months or so it failed to start again.
I think it may be a defective heat sensor,but I can’t find it on a schematic.I did replace the electric fan motor assembly at a whooping $750 cost.I had noticed that the fan motor would spin at hi RPM when it wouldn’t start .Now the fan does rev ,but I still have “no start” episodes.
Any thoughts?