Nd. help with elec. problem, "load shedding" relay?

jmackro

jmackro

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My coupe suffered a weird electrical glitch on the drive back from Monterey. The car is an early 2800 e9, US delivery model, manual, s/n 2270335. I believe the problem was caused by a malfunctioning voltage regulator that put about 17 volts into the battery. This fried the Pertronix unit as well as the battery. When I got the car home after a 161 mile flatbed ride, I began to sort out the problems.

Substituting points for the Pertronix, the old mechanical regulator for the solid-state unit, and installing another battery got the car running and charging OK. However, a number of electrical items are still not working. I checked all of the fuses, and found one obvious problem: fuses #8 & 9 are not getting power.

Here’s what doesn’t work: tachometer, clock, fuel gauge, electric windows, heater blower, A/C blower, headlights (with the HL switch fully out, the parking lights come on, but not the main bulbs).

Here’s a partial list of what does work: the temp gauge (which is in the same housing as the fuel gauge), charging light, oil pressure light, brake lights, parking lights, back-up light, turn signals, horn, windshield wipers.

I am using one of the wiring diagrams from Prospero’s Garage – according to that diagram, fuses #8 & 9 correspond to many of the non-functioning items. Something called the “Load Shedding Relay” on the wiring diagram appears to provide power to fuses #8 & 9, so I’m wondering if this could be part of the problem; does anyone know where this relay is located, and how to reset it?

For the items not powered by fuses #8 & 9 (tachometer, clock, fuel gauge) does anyone have any ideas of why they might be nonfunctional even though their fuses are hot? (Yea, I know – the overvoltage may have fried them).
 
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Jay,

I am very sorry to hear that this happened. I have a fuel and temp gauge that you can have if you would like to try it out. I am in Newport/Mesa. Send me a PM if interested.


Thanks,
Mike
 
You'll have to check all the relays under the hood around the battery and also the ones under the dash in the left glove compartment. That's where they are in my '74...I don't remember which is where, and they may vary by year. I think there is a "main" relay which turns on when the ignition is on and feeds fuses 8 and 9 if I remember correctly (I'm on vacation and can't get to my car...) This relay is probably one of the four or five under the dash. Hope this helps.
 
Bummer.

The load shed relay should be a rectangular box mounted just below the fuses. It only has 4 wires: gound (18 gauge brown), coil energize (18gauge), power in (10 gauge or larger) and power out (also large).

The good news is that most things on the coupe are not solid state and the odds of burning something out with 17 volts are small. However, a relay coil can fry given enough time at too high of a voltage. So far the only solid state stuff I know about are the fuel / ignition controllers (if you have them) and the turn signal / flasher relay which uses a transistor timing circuit.

If you find the load shed relay you can do a couple of quick checks. With the ignition on, both heavy gauge wire sides of the relay should have 12 volts. Also, the small gauge (not brown) coil energize lead should 12 volts.

- If one of the heavy gauge wires does not have voltage then the relay is probably dead.
- If the energize lead does not have 12 volts you can try directly applying 12vs to it. You should hear the relay click. If not, the coil is probably burned out. You can also measure the coil resistance (across small leads) with the leads removed. It should register something less than 10 ohms.
- If the the energize lead has power and you hear clicking (ignition on/off or bypass lead) you may have a broken contactor on the high current path. This is unlikely given the failure scenario but I have seen this.
- You can also directly connect the two heavy gauge leads together to bypass the relay. If this makes things work again then the relay is definitely bad. I suspect these relays are available but if not it should be possible to install a newer relay to replace it. I don't know the current rating but we can figure it out and find a suitable replacement.

Keep us posted.
 
I would rule out any wire harness meltdown just to have peace of mind. Maybe diagnose the electric windows because there should be no damage to the motors, and the voltages are accessible easily at the switches.

I am afraid this setback may require you to sell one of your Alfas so you can focus your time and resources on the E9. Sell me one of your Alfas, I mean...
 
JJ:

I see the relay you refer to - the one directly under the fusebox. It does have four wires going into it: brown = gnd, black = energize, green/brown = +12V in, green/brown = +12V out. However, it doesn't function as I would expect it to.

When I turn on the key, the black wire doesn't get energized, nor does the relay click. Yet, if I disconnect the black wire, and just jumper +12 to that pin, the relay does click. Also, the heavy gauge green/brown wire that appears to be the source of power is not live. So, even if turning on the key did energize the relay, it wouldn't power the windows and A/C.

If I disconnect the heavy gauge green/brown wire that appears to be power out, and energize it with +12, the A/C and power windows will function.

I am puzzled by the fact that I don't have a source of power to this relay. Is there a "master fuse" or circuit breaker anywhere in this circuit? I suppose my ignition switch could also be flakey, and not providing power to this relay. But, it has been my experience that multiple faults don't occur simultaneously, so I am trying to come up with one thing that could cause these odd symptoms.

Arde:

Gee, I was just thinking of how much simpler the Alfa's wiring is, as compared to the CS. If I'd taken the Sprint GT up to Monterey this year, as I did last, I might have avoided AAA.
 
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hmmm

I've wondered about that LSR for a bit.

LSR function is to cut power to circuits when the starter is engaged so all the amps go to the starter. I would expect that the "power in" circuit is hot when the ignition is on, and the black "energize" wire (using jhjacobs description) comes from the same terminal as the one from the ignition switch to starter solenoid.

Functionally, other circuits (windows for example) will work with the key on, but not while the starter is engaged. In turn, this means that the LSR cuts power when activated, but this is unexpected ... auto relays ordinarily are "normally open" and are used to energize circuits, though there is no reason not to think that they couldn't be used the other way around as a "normally closed" type.

Am I right here?
 
I don't think the LSR is supposed to disconnect during starting; I believe the main purpose is to reduce the amount of current that needs to flow through the ignition switch. I only say this because the LSR energize and coil are powered from fuse 6 (so the ignition turns off when the LSR is off). I may be wrong but I'll check.

The LSR energize signal (85) comes directly from fuse 6. I would need to pull out my fuse box to be sure but I think fuse 6 is powered directly from fuse 7 which is enabled by the ignition switch. (I think they are tied in the back of the fuse box - BMW did many little tricks like this that do not appear on the schematics; similarly, I think fuses 8 and 9 are also tied in the back).

The LSR primary input power come directly from the battery on pin (30) - if there is a fuse it is in-line. I know there is an in-line fuse somewhere in the engine bay but I don't recall the circuit, now I guess I'll need to look because this could be the source of the problem! The LSR output (87) goes with fuse 9 which is in turn ties to fuse 8 (in the back).

So, to answer your question about a master fuse, if the relay is not energizing look at fuses 6 and 7. The ignition should turn on fuse 7 and fuse 6 should also activate and thereby activate the LSR. I am going to take a closer look at my relay box to see if 6 and 7 are tied. You can actually pull out the fuse box fairly easily to look behind it; it has a few screws and when removed there is some wiggle room - just make sure you have disconnected the battery first.

Now I need to go and confirm my bold statements. :?
 
jhjacobs had written:

"if there is a fuse it is in-line. I know there is an in-line fuse somewhere in the engine bay but I don't recall the circuit, now I guess I'll need to look..."

Any info JJ or other folks on the Forum might have on this would be greatly appreciated. The power source to the LS relay appears dead, and I'm puzzled where that wire originates. Pulling the fusebox may be the next step.

This would solve half of my problem - the other half is why no signal is getting to the relay. If the signal comes from fuses 6 & 7, I'm puzzled why the wire isn't getting energized, as those two fuses are hot when the IG switch is on. But, the black wire doesn't appear to originate at the fusebox - it comes from the right as you look at the fusebox, suggesting that it may come off the ignition switch and not the fusebox. I will remove the lower shround beneath the ig. switch tomorrow, and explore this further. I did try wiggling the key in the switch today, in an attempt to diagnose a flakey IG switch, but couldn't get any voltage on the black wire that energizes the LS relay.

Yes, it would make sense that fuses 6 & 7 and 8 & 9, are tied together as pairs. 6 & 7 both have low ampere loads that come on with the key, while 8 & 9 have high amp loads that logically would be energized by the LS relay.
 
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Well I have to eat some crow here. The LSR is a Normally Closed relay which opens when the starter is activated just like Hon suggests. My schematics are wrong which is no surprise. :oops:

However, I have confirmed that fuses 8 and 8 are bridged connected on the top side. Also, 6 and 7 are bridged on the top as are 4 and 5.

Now, I am trying to determine where the LSR energize signal really comes from. The wire is black which suggests it is circuit 50 from the ignition switch, the one to activate the starter. This would cause it to open when the starter is turning to allow more power to the starter.

I really am curious now. I have no idea where the power to the relay comes from either; my schematics (3 so far) shows a direct path to the battery. I have two more schematics to consult. More to follow as I rat this thing out. :evil:
 
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Well, I was wrong and right. I was right about the LSR operation, it does always stay engaged when the ignition is on and it's purpose is to protect the ignition switch. I was wrong about which relay was the LSR. The LSR is the rectangular silver relay mounted behind the turn signal relay, just above the hood release. The relay below the fuses is still a mystery. Based on the wire colors it may actually perform the function Hon suggests. The black circuit is supposed to be the starter solenoid energizer and a black wire energizes this relay and it is a NC relay. The other heavy wires are green/red and green/?? which suggest the feed to fuses 8&9. However, on my coupe this relay does not do anything when starting the car (it stays in the NC position). Given the size of the wires it suggests that is carries a healthy load.

So, back to the problem at hand. My original notes do apply but the LSR is in a different location per above. The relay under the fuses should have voltage on both heavy wires when the ignition is on. If fuses 8&9 have power when the ignition is on then the LSR (and the likely the other relay) are fine.

There is nothing like bogus documentation to make life interesting. :confused:

I will go and check for the in-line fuse next. I believe it is hidden somewhere near the coil.
 
I was able to locate the in-line fuse. It is below the coil on the output of a relay. It feeds into a wire bundle going to the front of the car. My best guess is that it is a fuse for the electric fan that is supposed to come on when the AC is active. None of my schematics show anything about the AC circuit so I suspect BMW never really thought about AC as a standard item so it didn't deserve formal documentation. I'm beginning to think that the load shed circuit involves two relays, the first relay engages to save the ignition switch and the second stage disengages when the starter is active (even though mine doesn't seem to do this). This would make sense but it is clearly not documented :?
 
Well, I've done some more debugging, and at this point am totally baffled. I think that professional help is the next step.

The relay below the fuseblock really has me puzzled - it IS a NC relay. The contacts with the heavy gauge wires are normally connected; applying +12v to the signal contact causes the power contacts to disconnect. However, the signal wire does not actuate with the starter, nor with the ignition switch. Believe it or not, it actuates with the A/C controls. This is really weird because the A/C is one of the accessories powered by the green/yellow wire that comes off this relay.
 
I may just be adding to the confusion, but the electrical diagram that most closely resembles my car (!), the "from 1973 on" one, shows that there are 3 load shedding relays. One primary that's connected to the ignition, and an additional pair that are both for the power windows, sort of ganged, so that one is switched by the door contact, and the other by ignition. It really takes a lot of patience to trace the connections.

And if your model includes the circuit breakers for the windows in the under-dash panel, check to make sure that one hasn't popped, because they're included in the circuit.

Charlie
 
Last 2 relays in previous message

Those 2, which deal with the door window mechnisms on >73 cars, as you say, are mounted in a neat row above the bonnet release handle, on the left side. They are #2 and 3 counting from left to right. I have them on my 74 car but not on my earlier cars.
One apparently allows the driver´s window (perhaps all 4?) to be operated without the ignition being on, but ONLY when the door is open !!!!!
 
Charlie and Phil:

Thanks for the suggestions, but my coupe is a 1970 - its window circuits are much simpler. In fact I have the Prospero's wiring diagram for pre-1973 e9's and even it seems too modern.
 
Wiring and Relays

Jay,

The Prospero diagrams are handy but only the Blue Book diagrams have the exact color codes and relative locations of each item. At least you are fortunate to have the earlier and simpler wiring. I borrowed one of the Blue Book diagrams from Spence and made a copy at Kinkos which I enlarged several times.
 
OK, I got the problem solved - here's what I learned:

The load shedding relay does look like the one described in jhjacob's post of Aug 17th - e.g., its cross-section is sort of a rounded off rectangle. However, it isn't located below the fusebox (that's the A/C relay). The load shedding relay is above and to the left of the fusebox, above the hood release lever and ahead of the windshield wiper washer relay.

Mine was melted from the overvoltage condition - my local shop, EuroTech in Mission Viejo located a used spare, plugged it in, and I'm good (well, a few gauges are still fried, but at least the car is drivable again).

Thanks for all the help!
 
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