Welcome to the world's #1 Volvo forum!

Volvo Fixes & Advice since 2001.

Login Register

B+ terminal repair - main fuse box

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, including 850 R, 850 T-5R, 850 T-5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

Post Reply
DGM
Posts: 459
Joined: 23 Dec 2010, 05:20
Year and Model: V70 2.4i 2005
Location: Quebec, Canada
Been thanked: 1 time

Volvo Repair Database B+ terminal repair - main fuse box

Post by DGM »

I am a new member on Matthew’s Volvo site. I would like to share a repair I made recently. This is my contribution for being new on this forum.


S70 1998


Symptoms

Headlights intensity lower when rear defroster is used or when ABS activates. Lights are dimming in dash pod when electrical system is stressed. ECC unit lights flashes after car is started in freezing condition. Starter motor turns normally and alternator is charging well.


Cause


B+ terminal has become resistive under main fuse box.


There is a voltage drop of .5 volt or more between the battery B+ terminal and main fuse box. This is measured under load, blower fan to maximum, rear defroster on, heated seats on with engine idling.


Find photos showing repair and sequences of events;



1- Main fuse box under hood

Image


2- Cable feed from battery to main fuse box

Image

3- Cable terminal under fuse box cover

Image

4- Lost of .5 Volt. All the vehicle electrical current goes through this terminal (except for main starter feed).

Image

5- Under hood undress for repair

Image

6- It shows the overheated terminal at main fuse box. It is resistive and heats under load

Image

7- Terminal end cleaned up with flux paste and soldered instead of being only crimped. Heat shrink installed to improve insulation

Image

8- Drilling location for an additional cable to improve robustness

Image

9- 6 AWG cable (fine wires) with grommet

Image

10- Repair is ongoing

Image

11- Crimped & soldered terminal for the main fuse box

Image


12- Installed cable to reinforce the original circuit

Image

13- Protective tubing under the air-box filter

Image

14- Engine compartment back to normal

Image

15- New reading of 50 milivolts with the same load as before

Image

16- Heat test under load. The connexion is cold.

Image

17- Drill bit of 7/16 " for the hole

Image

18- Terminals

Image

19- Crimping tool for terminals / borrowed to a friend

Image

20- The other half who is claiming her vehicle back. Note the sparkling eyes of car and owner :D which indicates an electrical system in shape.

Image

You would need about 42" of 6 AWG cable of good quality (fine wires). A good alternative will be 4X lengths of 14 gauge (fine wires). You will gain in flexibility during the installation in the fuse box. There is very little space.

Terminals;

Napa 784581, 1 X but sold in 10 units per box. Around 4$
Standard BP 303, 1 X for .75 cents

You can find equivalent terminals locally at your AutoParts

The original wiring is an integral part of the car harness , it is hard to remove for repair. The wiring length isn’t sufficient to support the installation of new terminals.

I have decided to repair the existing one and add reinforcement. It costs me little since I already had the cable and protective tubing. Count 2 hours of your time if you have the material and tools.

http://www.powerstream.com/Wire_Size.htm
http://www.allworldauto.com/tsbs/NHTSA_ ... 24059.html

I think we would be surprised of the number of S/V70 on the road having this problem at high millage.

It is a good idea to verify if you have this voltage drop & if the terminal overheats in the main fuse box. This will give you a good indication of the wiring condition.

Since I made the repair, the overall car driveability has improved and everythings is now back to normal. Blower fan comes on strong after start up.

:)
Last edited by DGM on 31 Jan 2016, 09:35, edited 3 times in total.
V70 2005 2.4i 195,000km, sold
S70 1998 T5 355,000km, sold
960 1994 80,000km, sold
760 1990 Turbo 265,000km, sold

JRL
Posts: 9350
Joined: 22 Nov 2005, 14:07
Year and Model: Several
Location: 19333
Been thanked: 13 times

Post by JRL »

Good write up
I've been telling people for two years now that their B+ cable is probably bad.

HOWEVER...
It's better just to buy the complete cable from Volvo as it's not just the ends that go bad
2000 V70R Black, 144,000 miles Wife's R.
2007 V70 2.5T White/Oak 111,000 MILES. Polestar tune, IPD bars, rear spoiler, dark grey Thors, DWS 06, HU850, sub.

Contact info for purchases: jrl1194@aol.com

RyanGLT
Posts: 185
Joined: 06 Nov 2010, 15:28
Year and Model: '07 XC90 V8 AWD
Location: Topeka, KS

Post by RyanGLT »

I have been wanting to see someone with pictures of removing the main fuse box from an 850. I tried to when I first bought my wagon and I was unsuccessful. there has to be a trick to it, but I don't know what it is.
'07 XC90 V8 AWD

DGM
Posts: 459
Joined: 23 Dec 2010, 05:20
Year and Model: V70 2.4i 2005
Location: Quebec, Canada
Been thanked: 1 time

Post by DGM »

RyanGLT wrote:I have been wanting to see someone with pictures of removing the main fuse box from an 850. I tried to when I first bought my wagon and I was unsuccessful. there has to be a trick to it, but I don't know what it is.
I just looked at the wiring diagram of the 850 and it is much different than a S/V70. Many feeds are distributed from the battery to the different circuits (fuses).

On the contrary in the S/V70 arrangement, 4 wires are pulled together to the main fuse box for distribution. Their termination is the weak point because their ends are only crimped on a terminal. This make a weak electrical contact that is proned to heat.

For the fuse box on the 850 i have never found a trick to access it other than from under.
V70 2005 2.4i 195,000km, sold
S70 1998 T5 355,000km, sold
960 1994 80,000km, sold
760 1990 Turbo 265,000km, sold

DGM
Posts: 459
Joined: 23 Dec 2010, 05:20
Year and Model: V70 2.4i 2005
Location: Quebec, Canada
Been thanked: 1 time

Post by DGM »

JRL wrote: HOWEVER...
It's better just to buy the complete cable from Volvo as it's not just the ends that go bad
I think you are refering to B+ cable between the battery and the starter motor. This one is available as a cable assembly with a preform terminal at the battery post. I find it a better solution than just replacing the terminal as i did a few years ago.

However upon verification with my local Volvo dealer they could not come up with another solution than installing a "service cable" as i did to fix the heated terminal. Originally four wires are wraped together as a single cable to carry the current to the main fuse box. These wires are an integral part of the vehicule harness. Opening the wiring harness to replace them isn't partical. May be someone has or will developt another approach to it. Definitly the B+ terminals are something to watch for on the S/V70 model in my opinion :).
V70 2005 2.4i 195,000km, sold
S70 1998 T5 355,000km, sold
960 1994 80,000km, sold
760 1990 Turbo 265,000km, sold

reds70turbo
Posts: 89
Joined: 17 Dec 2010, 07:40
Year and Model: 1998 Volvo S70 GLT
Location: Lancaster, PA

Post by reds70turbo »

Those pictures gave me a not so friendly flash back. I have done this repair on my own car, only I used the Volvo B+ cable which runs around $60 bucks. I actually ended up with a new alternator, battery, B+ cable, alt. to starter & starter to battery cables and a ground harness. All were Genuine Volvo parts. Goodbye electrical gremins. :lol:
1998 S70 GLT - 183K - full of fun stuff and meticulously maintained!

JRL
Posts: 9350
Joined: 22 Nov 2005, 14:07
Year and Model: Several
Location: 19333
Been thanked: 13 times

Post by JRL »

DGM wrote:
JRL wrote: HOWEVER...
It's better just to buy the complete cable from Volvo as it's not just the ends that go bad
I think you are refering to B+ cable between the battery and the starter motor. This one is available as a cable assembly with a preform terminal at the battery post. I find it a better solution than just replacing the terminal as i did a few years ago.

However upon verification with my local Volvo dealer they could not come up with another solution than installing a "service cable" as i did to fix the heated terminal. Originally four wires are wraped together as a single cable to carry the current to the main fuse box. These wires are an integral part of the vehicule harness. Opening the wiring harness to replace them isn't partical. May be someone has or will developt another approach to it. Definitly the B+ terminals are something to watch for on the S/V70 model in my opinion :).
No, that's the starter cable.
I never had to replace a bad cable in an 850, just 99 and 2000 70 series. (1998 B+ cables are usually OK for whatever reason)
The B+ is what goes to the fuse box and is considered to be part of the car's wiring harness and it usually covered under extended warranties
2000 V70R Black, 144,000 miles Wife's R.
2007 V70 2.5T White/Oak 111,000 MILES. Polestar tune, IPD bars, rear spoiler, dark grey Thors, DWS 06, HU850, sub.

Contact info for purchases: jrl1194@aol.com

User avatar
matthew1
Site Admin
Posts: 11596
Joined: 14 Sep 2002, 11:03
Year and Model: 850 T5, 1997
Location: Denver, Colorado, US
Has thanked: 993 times
Been thanked: 422 times

Post by matthew1 »

DGM, great writeup. I put it in the Repair Database and made your account MVS Contributor status.
Help keep MVS on the web -> click sponsors' links here on MVS when you buy from them.
Also -> Amazon link
. Click that when you go to buy something on Amazon and MVS gets a kickback.

1997 850 T5, MSD ignition coil, Hallman manual boost controller, injectors, R bumper, OMP strut brace [gone]
2004 V70 R [gone]

Image

DGM
Posts: 459
Joined: 23 Dec 2010, 05:20
Year and Model: V70 2.4i 2005
Location: Quebec, Canada
Been thanked: 1 time

Post by DGM »

Thanks it is appreciated.
Last edited by DGM on 29 Jan 2011, 05:48, edited 1 time in total.
V70 2005 2.4i 195,000km, sold
S70 1998 T5 355,000km, sold
960 1994 80,000km, sold
760 1990 Turbo 265,000km, sold

cn90
Posts: 7134
Joined: 31 Mar 2010, 09:54
Year and Model: 2004 V70 2.5T
Location: Omaha NE
Been thanked: 206 times

Post by cn90 »

Thank you for the nice DIY!

This gives me incentive to inspect the Main Fuse Box wiring once in a while.

My comment: if you run an additional cable (keeping the original multi-wire cable as shown in Step #6), then I do not think you need a 6G cable, maybe 10G is good enough, just a guess.

The other option is to get rid of all those multi-wire cables (in Step #6), and replace with the single 6G cable as you mentioned.
2004 V70 2.5T 100K+
2005 XC90 2.5T 110K+

Post Reply