1998 s70 reverse jump polarity troubleshooting. Bad relays Topic is solved

Derbyrunner · Post by **Derbyrunner** » 17 Aug 2016, 06:43

Ok so I bought a running and driving 1998 S70 turbo and had to use a loaner battery to get it started and test drive. Car ran with no issues. Get it home and my teenage son who I bought car for hooked up new battery backwards. Now engine will not even turn over and the 15 amp fuse blows as soon as key is turned on. Need help badly

Post by **cn90** » 17 Aug 2016, 08:34

This has been reported before (reverse hookup), search forum for solutions, I think it is about checking a whole bunch of fuses.

Post by **abscate** » 17 Aug 2016, 09:01

This usually takes out the voltage regulator on the back of the alternator. Its actually good that it does this as this can get much more expensive than this.

Derbyrunner · Post by **Derbyrunner** » 17 Aug 2016, 14:54

abscate wrote:This usually takes out the voltage regulator on the back of the alternator. Its actually good that it does this as this can get much more expensive than this.

Is there a way to test voltage regulator?

Derbyrunner · Post by **Derbyrunner** » 17 Aug 2016, 18:33

Changed voltage regulator and car still blows ignition fuse.

Post by **abscate** » 17 Aug 2016, 18:42

Ugh. You will have to find the right wiring diagram on the inter webs and trace that fuse and all circuits on it to find the fault.

Post by **BEJinFbk** » 17 Aug 2016, 20:32

It would be helpful if you identified the fuse slot #.

Derbyrunner · Post by **Derbyrunner** » 18 Aug 2016, 16:56

Fuse number 10

Post by **cn90** » 18 Aug 2016, 19:20

Fuse #10 controls:
Ignition switch, Control modules - engine/automatic transmission 10 A

http://new.volvocars.com/ownersdocs/199 ... 70_102.htm

So it is down to:

1. A short in the wiring somewhere.
2. A short inside the ignition switch (which is extremely rare, almost unheard of).
3. A short inside the ECU, almost unheard of.

Please post a follow-up.

Post by **BEJinFbk** » 18 Aug 2016, 21:59

That's the fuse that actually feeds the ignition switch itself.
From there it branches out to several things, including accessory
overload relays 105 and 106.
One way to deal with this is take a picture of the fuse box,
pull all of the other fuses and start putting them back one at
a time with the key on. Long way around, but it's a start.

This may help:

98 S-V70 Fuse Locations and Legends.pdf: (678.65 KiB) Downloaded 237 times