Large electrical problems

tintti · Post by **tintti** » 31 Mar 2018, 05:22

Hi,
This is my first post to this forum, which I have found very helpful.
I live in southern Finland where the roads are salted every winter causing rusting and corrosion.
The car mechanically is in working condition, with about 210 000 miles on it. The electrical problems have been growing with the last few years. Initially, in the winter the car would blow the fuses of our house when connected to block heater via external cable. About a half year later the V70 started dimming lights while driving. For example, If I were to lower my window, the headlights and the interior lights would dim.
This winter the headlights have been acting very oddly, sometimes when starting, the headlights would not turn up until switching it on and off fiercely. Also the engine would drop below from the normal 1000 rpm to about 500 rpm when coasting, sometimes even stalling. Now the headlights stay on even when the engine is not running and the doors are shut. I have overcome this by taking the headlight fuse of when parking, but I reckon that something should be done.
From my understanding, could this be a grounding issue? Or maybe the CEM unit is at fault with malfunctioning lights?

Thanks in advance for all the responses. I have found topics regarding some of these problems, but not all.
Any advice would be helpful

Post by **regent** » 31 Mar 2018, 10:52

Welcome to the forums!

Since you have salt all the time, a corroded connection would make a lot of sense... could be on the positive or the negative (ground) side.

I would begin simple: inspect both battery terminals and cables (+ and -), also the B+ terminal at the main fuse box inside the engine compartment, look for corrosion, discoloration and loose connections. Check the charging system and the battery. If all checks good, then stert looking at the grounding points. You will need to have the electrical schematics for specific groung point locations

Post by **regent** » 31 Mar 2018, 11:05

See if you can download your schematic from this site:
http://www.volvowiringdiagrams.com/

(from where I am right now, I could not do that, hope you have better luck)

tintti · Post by **tintti** » 01 Apr 2018, 06:56

Thanks for the quick response and the link!
I have now checked the battery terminal, which reads steady 14.12v when the engine is running, and steady 12.10v when engine is off. In the front, I measured from the B+ terminal to the yellow ground wire which connects to the chassis. I suppose this is okay? The voltage from the terminal was inconsistent, variating from 0 - 14.15v and something in between as the engine was running. When the engine was off, it gave a steady 12.13v measurement.
I think there is something wrong with the B+ terminal if I have measured correctly. As next step I will try to find the ground terminals from the wiring diagram and clean the contact points. Would you have any suggestions? Thanks in advance.

edit: some errors in the measurements

Post by **regent** » 01 Apr 2018, 09:35

I think you are on the right track, find the source for that fluctuating voltage reading; given the exposure to salt, I would suspect to find more than just one corroded point.
A generic handheld infrared remote thermometer (if you have one) will help locate a poor electrical joint. Increased resistance in a joint will result in higher temp because of heat dissipation (current squared times resistance = heat ). Easier for me to spot check than touching everything with a voltmeter

I got mine for $12 or so on ebay years ago

The B+ terminal that powers the main fuse box is a known famous offender. Look at that one very closely (with battery disconnected). Could be the only culprit.

tintti · Post by **tintti** » 07 Apr 2018, 02:11

I have now cleaned all the grounds (and connectors) I could find in the engine bay and ran it through OBD reader. The block heater was indeed corroded and thus burned fuses. But it seems like the other malfunctions are separate problems. The OBD reader gave a code P0032, which is the oxygen sensor control unit, but I suspect that the Lambda sensor just needs to be replaced as the yellow engine light in the dashboard suggests. About the other electrical gremlins I'm now suspecting the Light Switch Module. Without the main headlight fuse, the car runs just well around the 1000 rpm, so the LSM might be overloading something.
Thanks for your guidance

! I'll report back if that was the problem so others with the same problem can know.

Post by **regent** » 07 Apr 2018, 15:43

Our oxygen sensors usually start deteriorating around 120 kMiles or so; I replaced mine around 150 kMi while the car was in the air for suspension work. Though I did not have MIL or O2S codes, my gas mileage was getting not as good.

Post by **RickHaleParker** » 07 Apr 2018, 17:17

steady 12.10v when engine is off.

12.10V = ~ 60% discharged, way to low for a starter battery. I would check out the battery and the charging system first.

Post by **oragex** » 07 Apr 2018, 17:35

tintti wrote: 01 Apr 2018, 06:56 Thanks for the quick response and the link!
I have now checked the battery terminal, which reads steady 14.12v when the engine is running, and steady 12.10v when engine is off. In the front, I measured from the B+ terminal to the yellow ground wire which connects to the chassis. I suppose this is okay? The voltage from the terminal was inconsistent, variating from 0 - 14.15v and something in between as the engine was running. When the engine was off, it gave a steady 12.13v measurement.
I think there is something wrong with the B+ terminal if I have measured correctly. As next step I will try to find the ground terminals from the wiring diagram and clean the contact points. Would you have any suggestions? Thanks in advance.

edit: some errors in the measurements

14.1 when running is on the weak side, it means the battery is not at it's best shape (as noted above 12.1 is weak for a battery even if the car still starts easily - the battery is worn and won't fully charge any more, you should have at least a 12.4 and at best some 12.6-12.7). The regulator will pump less voltage when the battery is worn. But what's the most important thing here is to find the current leak/parasitic drain before you replace the battery. The way it goes is a parasitic drain will drain the battery overnight then the alternator will recharge it back again when the car will run: this is what damages a battery: charging and discharging cycles.

Try just to measure the battery at off after a short trip then again the next morning before starting the engine, see how much it has lost due to the parasitic drain. This video shows how to find a parasitic drain. You'll need a voltmeter with a 10A current function.

If there is no parasitic drain, then I'd replace the battery and quickly test the alternator voltage again when running: if it shows 14.4V and up, it means the alternator is charging properly. If it's less, then the alternator may have a problem (worn) and it must be replaced quickly before it ruins the new battery.

Of course, all this after you've checked all cables (cracked), connections (corrosion), etc.

Post by **sleddriver** » 07 Apr 2018, 18:27

Tintti: As you live where Winter roads are salted, be sure top of battery is clean & dry. It is possible to form a dry "salt bridge" across the top between the two terminals from a combination of salt crystals/dust/dirt/dampness you may not even notice until looking closer. Same goes for the starter.

I agree with the others...your batt voltage is low.