Electrical issues 850 T-5R

MrTomLegit · Post by **MrTomLegit** » 15 Apr 2021, 14:11

Hello Everyone,

I am looking into potential issues with my 1995 850 T-5R. I am having an issue where sometimes coming off the gas, the car will stall, dash lights up like a Christmas tree and then is hard to start. The other key part of this that may be related is that my radio will blow a fuse instantly. Things that have been changed as troubleshooting:
New battery last year
Alternator was replace approximately 3 years ago by reputable indie
Positive battery cable replaced.

Clearly the Radio is shorting out, but I am curious if it is related to the issue or just a red herring and how on earth to track down the short.

Next steps I had in mind were checking ground wires but not sure where they all are: viewtopic.php?t=42915
Located this thread, His vehicle was listed as a 2000 V70, does that apply to my 850?

Lastly, I have a voltmeter, but my experience using it is near 0 as it was a hand-me-down. It does work. So I would need some guidance on where to test using what settings on the voltmeter.

Thank you for taking the time to take a look.

Post by **volvolugnut** » 15 Apr 2021, 14:55

Here is a basic introduction to using a voltmeter on a car. https://www.youtube.com/watch?v=c9KNAIjoEYs

You will need to find an electrical schematic for the model and year of your car. They change a lot from model to model and even year to year.

I suggest you first find and remove the fuse for the radio. Track down your fuse box or boxes (you will need this later if you check with the voltmeter) that contain the radio fuse. Note that the radio fuse may also be used for other electrical devices. It may be in common with your dash and instrument lights.

Others will have to give you more detail on specific tests for your car.

volvolugnut

Post by **BEJinFbk** » 15 Apr 2021, 18:17

Your heading the right direction checking
all power and ground cables between the
battery, starter and alternator.
There’s also a 10 gauge from the battery
to the main fuse box to check both ends of.

Another thing that may be an issue is the
electrical part of the ignition switch. The
way you described the failure might be
tied to the ignition switch if you have an
overloaded key ring swinging around.

MrTomLegit · Post by **MrTomLegit** » 16 Apr 2021, 07:29

BEJinFbk wrote: ↑15 Apr 2021, 18:17 Your heading the right direction checking
all power and ground cables between the
battery, starter and alternator.
There’s also a 10 gauge from the battery
to the main fuse box to check both ends of.

Another thing that may be an issue is the
electrical part of the ignition switch. The
way you described the failure might be
tied to the ignition switch if you have an
overloaded key ring swinging around.

I did the ignition switch about 5 years ago with a brand new one. Hopefully that one is not going bad. But I know they are prone to fail.

Post by **BEJinFbk** » 16 Apr 2021, 08:01

As far as the radio, is it stock?
Have you been into the dash behind
it and confirmed that the harness
hasn’t been hacked up from this
or previous audio systems?

And which fuse is blowing?
The radio has two - 7 & 32.

MrTomLegit · Post by **MrTomLegit** » 16 Apr 2021, 08:11

BEJinFbk wrote: ↑16 Apr 2021, 08:01 As far as the radio, is it stock?
Have you been into the dash behind
it and confirmed that the harness
hasn’t been hacked up from this
or previous audio systems?

And which fuse is blowing?
The radio has two - 7 & 32.

Radio is stock. Only time there has been work done in that area was when I did the heater core about 5 years ago. I'll pull it out and look. I am doing post winter items on it this evening. I believe it is fuse 7, but I will confirm.

Post by **BEJinFbk** » 16 Apr 2021, 15:00

IiRC, 7 is the switched power and there
may be some other things on it. I’ll have
a look when I get back to a bigger screen
this weekend.

MrTomLegit · Post by **MrTomLegit** » 16 Apr 2021, 17:38

BEJinFbk wrote: ↑16 Apr 2021, 15:00 IiRC, 7 is the switched power and there
may be some other things on it. I’ll have
a look when I get back to a bigger screen
this weekend.

I confirmed standing voltage on 7. Nothing connected and key out. Pulled the radio out and besides looking old, nothing was really exposed. I had a Ham radio installed, but I completely disconnected it a while ago.

I didn’t splice into any wires to install it. I just used the accessory ports under the driver seat. That was working fine when I pulled it.

I am sitting at 13.4v with headlights on and driving. It dips to maybe 12.5 when I let of the throttle instantly, but also jumps back up instantly right back.

MrTomLegit · Post by **MrTomLegit** » 18 Apr 2021, 12:59

Did a bit more digging on this and found this thread: viewtopic.php?t=93366

Looks like there could be a chance that the amp is bad. That is my next troubleshooting step to see if the voltage goes away with the amp out. I have been going back and forth on replacing the head unit for a while now regardless.

Will report back of this makes any noticeable difference.

Another side note: Autozone replaced my battery under warranty Thursday and I have not really had the nearly dying when coming off the throttle, but I may still be too early to tell. There is still very obviously an electrical issue.

Post by **misha** » 18 Apr 2021, 13:11

13.4v at battery terminals when engine is idling with headlights is too low.

It should be 13.8-14.2v with headlights,heater blower on(but not max) and radio...at idle.

B+ cable is the main culprit...but you will need to perform a voltage drop test when everything under the hood is warm....after 30min of driving and without turning the engine off prior testing.