Need advise / help

[Tom Gierisch]

Thanks for all your input.  The harness that comes off the fuse panel makes a 180 under the dash and splits with most of the wiring headed towards the drivers side. As you probably know the harness are massive and near impossible to lay your hands on.  I could see the wires coming off the two fusses. There are actually three wires which quickly disappear into a large bundle which would be near impossible to trace.   I'll check the resistance to ground on the load side of the fusses and lamp test as suggested.  I'll start daylighting the harness in the engine bay and start examining each wire. Maybe I'll have better luck on that end. This could be worse than looking for a needle in a hay stack.

My build date is October 1998

[Alie&Jim's Carrilite]

Have you checked where the harness goes thru the firewall?  And check the bottom side of the fuse panel.  

I'll pull my fuse cover in the morning and see if I can't trace anything for you.  

Have you unplugged the Drivers display?  Unplug it and see if you still blow the #12 fuse.

Edited November 7, 2020 by Alie&Jim's Carrilite

[Darryl&Rita]

2 hours ago, Tom Gierisch said:

There are actually three wires which quickly disappear into a large bundle which would be near impossible to trace.

If you can get the colour combinations off the wires, that will help locate them out in the field. They might be numbered, or have a main colour/tracer combination. It truly is a needle and haystack situation, but it's not hard.

[NeverEasy]

11 hours ago, Tom Gierisch said:

My build date is October 1998

Thanks for the info.  That puts you in 98 category for schematics.  I will look more when I get home this P.M.  That makes F30 your Flash-to-Pass fuse, not F27.  

 

[Alie&Jim's Carrilite]

13 hours ago, NeverEasy said:

Thanks for the info.  That puts you in 98 category for schematics.  I will look more when I get home this P.M.  That makes F30 your Flash-to-Pass fuse, not F27.  

 

Never made it into the truck today...

Is the Flash to pass on the same circuit as the daylight headlight circuit.  I had the module that goes in the fuse panel short internally and it caused an avalanche of issues that David Dixon finally helped me figure out.  Unplugged the module and everything returned to normal.

[Tom Gierisch]

Weather is not to good today so my time outside has bee limited

The fuses have always blown with the drivers display disconnected. I'm not sure if that means if the fault is between the display and the fuse panel or not.  I guess I would be leaning toward the assumption that it is between the fuse panel and the drivers display if I had to guess. Both fuses read .85 ohm's to ground on the load side of each fuse with the multi meter set on 20K scale. ( I'm not an expert on resistance to ground and I'm not sure what that means) I would guess not good. When I tested the load side  from fuse to fuse  (12/27) I get zero oms to ground. That tells me the load side of the two fuses are common. I don't think that is a good thing!

I'm still looking at wire in the engine bay, haven't found anything out of order yet. 

The wiring under the dash looks in very good shape for a truck that is 20 years old. The insulation is soft and pliable with no cracking . I know that doesn't mean there can't be a problem in that area just saying Volvo has some good wire.

While waking up this morning I had a flash back to 2005 when I had the truck singled out. As I said earlier I think the circuit on fuse 27 always had a fault. As I remember I had an ABS warning light on after the front rear axle was removed. The shop foremen asked me if that light was on before he did the work and I told him yes and I believe it was. I was never able to get the light to go off after making several suggested checks, so I did a Larry Zigler for any of you that have been around that long. I removed the bulb from the panel and installed a burnt out bulb so I didn't have to look at it. Since both of these circuits (12/27) have to do with the instrument cluster maybe I should move my search to the rear axle. Thoughts on how to trouble shoot an ABS system are welcomed.

 

[NeverEasy]

Resistance of .85 ohms would equal 14.11 amps at 12VDC (Current = volts/resistance).  The load sides being common is not a good thing.  And both being at .85 ohms resistance to ground is weird.  

Your problem is not necessarily between the fuse panel and the display.

I really need to find these two fuses in a schematic.

 

 

[NeverEasy]

Big news here, I think:

F12 and F27 feed the QualComm Antenna.  They are shown on schematic V3_PV776_370_98094_1_QualComm_VN_B2_98.pdf.

The path for F27 and F12 is out on wire 950 and 951 through Connector 1 on pins C and B.  On the antenna side of that connector are yellow and white wires from the fuses and a black wire for ground.

Pin D is unused.

The connector is located under the dash on the center/right side.  Should be easy to locate once you see a 4-pin connector with a white wire, yellow wire, and a black wire, and one hole unused.

Click For Full-Size Image.

 

Click For Full-Size Image.

Edited November 8, 2020 by NeverEasy

[Darryl&Rita]

1 hour ago, NeverEasy said:

Big news here, I think:

F12 and F27 feed the QualComm Antenna.  They are shown on schematic V3_PV776_370_98094_1_QualComm_VN_B2_98.pdf.

The path for F27 and F12 is out on wire 950 and 951 through Connector 1 on pins C and B.  On the antenna side of that connector are yellow and white wires from the fuses and a black wire for ground.

Pin D is unused.

The connector is located under the dash on the center/right side.  Should be easy to locate once you see a 4-pin connector with a white wire, yellow wire, and a black wire, and one hole unused.

Click For Full-Size Image.

 

Click For Full-Size Image.

That there is pure gold. Qualcomm systems have never been known for tidy removals. Our KW had the remains of one left when we bought it. It wasn't causing any problems, but my OCD kicked in, and it all got removed.

[Tom Gierisch]

Dear Mr. Never Easy,

Thank you, thank you, thank you. One two wire connector was already disconnected on that harness. When I disconnected the second connector (4 pin) it cleared the faults and fuse 12/27 are not blowing. My assumption is that I do not need anything related to Qualcomm.  I hope that is the case. I really appreciate your time, knowledge, and skill to figure that out for me. I would have never have found that on my own.

Can I assume from your schematics that  the Qualcomm is the only thing on those two circuits?

I'm not sure if this was related to my intermittent loss of power but I am so pleased to not have fusses blowing, not knowing what they were for and not knowing why they were blowing. This was a learning exercise and I appreciate everyone's efforts. I also have lot's of new wire loom that looks good and found a few wires that were in need of a little TLC.

Now I think I'll tackle my ABS issue.

[Parrformance]

Remember something about putting the two extra ABS sensors in the single axle.

Fools the truck into thinking there are still two axles.

[Ray,IN]

Have you considered using a toner unit?

[Tom Gierisch]

I don't know what you mean by putting two extra ABS sensors in the single axle.

I don't know what a toner unit is.

[rickeieio]

If you had abs sensors on both back axles, when you single, put the two now unused sensors on the remaining axle.  Truck doesn't know an axle's missing.

By "toner unit", I believe he's referring to what's aka a tone generator.  A simple tool the you clip to one end of a wire and use a magic wand to find where the wire goes.  But, you don't need it now.

[Ray,IN]

53 minutes ago, Tom Gierisch said:

I don't know what you mean by putting two extra ABS sensors in the single axle.

I don't know what a toner unit is.

Click the hot link to a video showing how it works.

[NeverEasy]

Tom, You are welcome.  I know of no other systems that F12 and F27 feed.  You don't need the Qualcomm.  I took mine out years ago.

You can thank Mark Bruss for the schematics. 

Yes, I don't think those fuses would cause a a loss of power.  

One Miller Lite should we ever cross paths will be sufficient.  It was actually a pleasant journey for me.  I never fail to learn something and always live up to my handle.  

Chet

[DesertMiner]

You might check to see if you may have any other  remnants of a “Qualcomm” install. Lots of times when a “Qualcomm” is removed they just cut the wires and remove the pieces. Next time you have a minute remove the trim pieces that keep the floor mat down on the passengers side door opening. Lots of times that’s where they run the wires. Been stories  told of folks fixing the “electrical gremlins” In the rigs by checking those wires. 

[NeverEasy]

Tom,

As a side note, you now have two places to attach small electronics devices that will be fused by F12 and F27 and get their ground from that connector as well.  I am going to find mine again and use them to attach the DW's charging station for phone and electronics.  

F27 should be hot at all times.  Its source is from the battery connection on the starter, through a fusible link, through Maxi Fuse 10 (50 amps), the then to F27.

F12 is switched on by the ignition key.  Its source is the Ignition Power Relay PR3, through Maxi Fuse 3 (40 amp), and then to F12.

Chet

 

 

 

[NeverEasy]

14 hours ago, Tom Gierisch said:

Now I think I'll tackle my ABS issue.

You should start a new thread.  You sort of high-jacked your own by switching from fuses to ABS.  You might get more help from others if they are not following this link.

I will give you a starting point.  Basics as I understand them. 

There are two types of systems, Bendix and Wabco in use on Volvo.  Both function the same using an ABS ECU.  The ABS ECU (the brains) should be mounted on the frame, left side, forward of the rear wheels.  The ECU gets an input from each wheel by monitoring the wheel's speed with sensors on the wheel's hub.  That is where most of the problems reside.  The rotational part is a toothed wheel that passes a magnetic pickup.  As a tooth passes the magnet it induces a pulse that is sent to the ECU.  The ECU compares each wheel's rotation to the rest of the wheels and makes decisions and sends an alarm if things are not working as they should.  It then attempts to keep wheels from locking up during braking by using a modulator at each wheel to decrease breaking on a wheel that is turning slower than the others.  The ECU also monitors the rear wheels speed difference to incorporate traction control.  Traction control is the opposite.  If a traction control function is installed and switched on, the ECU uses the modulator to slow down a rear wheel that is turning faster than its counterpart on the other side thereby forcing the differential to apply even drive power to both sides of the truck.  

When removing an axle, the sets of wheel sensors (magnetic pickups) and modulators on one of the axles no longer have a use.  The modulator is an output of the ECU so removing it does not matter.  However, the ECU is still looking for an input from the pickup sensors on the removed axle.  The proper fix would likely be a change of the ECU from a 6x4 to a 4x2 (there are schematics for both so that makes me believe they exist) but that costs money.  The easy fix was to move the rear wheel sensors to the singled axle.  That way the ECU is fooled into getting pulses on both sets of sensors, left and right.  

I have not tried this, but I think an equivalent fix would be to simply parallel the wires from the removed axle sensors to the working axle sensors.  Those wires are not polarity sensitive so there should not be an issue with that.  The only concern would be signal strength but I believe there is enough signal strength to let the ECU believe that it has 4 wheels turning.   I put that here because someone may have trashed your back set of sensors.  You may only find wires.

This is where I would start.  Get the rear wheels off the ground.  Disconnect the sensor on a wheel and put a meter (set to low voltage if not Auto-Ranging) on the two pins of the sensor.  Spin the wheel.  There should be some low voltage present while the wheel is spinning.  My guess would be from 1.5 to 3 volts.  Then, do it on the front wheels.  If all is well there, you need to find the sensors (or wires) for the removed rear wheel and get them to lie to the ECU that they have a turning wheel.  

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