Automotive relay help

[DBecker]

What are the color bands on that diode?

Is it a 1N4102 8.7V 1/2 watt zener?  That would make sense for the circuit.

I initially thought that it was the same as the ABS relay used by BMW in that era, but it does appear to have a different purpose.

[dbert]

OK, so I've uncrossed my eyes and followed the diagram around a bit, so a few questions.  I also looked at your notes and they look right as far as I can tell at a quick glance.

What is the part called out as '181' ?

What are the exact symptoms observed with the car?  Are you actually seeing the +12V on pin 85 of relay 75e when cranking?  If you jump pins 30 and 87 does the ABS system then function normally?

181 is the ABS warning light on the dash.  It lights up in case of failure somewhere in the ABS system.

The +12V on pin 85 is present only when the key is turned to the "run" position.  This is not during cranking, but when  all the dash lights and radio come on.  Then when you turn the key to crank the engine (start position), the voltage is NOT present.  When the engine starts and you release the key, it goes back to +12V.

I haven't tried jumping 30 to 87, but it's crossed my mind.  I could be convinced to try it.

Here are the symptoms:

When I fire up the car and start driving, everything seems normal.  No warning lights, and braking is normal.  After several applications of the brake pedal, the hydraulic pressure drops below the minimum level.  At that point the "brake failure warning light" on the dash lights up.  Note this is not the ABS warning light, but the regular brake system warning light.  After about a dozen more brake applications, hydraulic pressure is so low that it suddenly becomes extremely difficult to stop the car.  Dangerously difficult.  Undriveable.

Here's the weird thing.  If I stop the car on the side of the road and turn it off, as soon as I turn the key off, the pump turns on and pressurizes the system again.  Obviously this is improper operation.  The pump should not be running with the car off.  It is supposed to run periodically while driving in order to maintain pressure in the system.  So it runs when the car is off, and doesn't run when the car is on.  This to me can mean only an electrical control issue.  Mechanically the pump and the low pressure switch are doing their jobs.

Now, it is entirely possible that one of the downstream relays is also malfunctioning, but before I go there I need to fix the problem with this relay first I think.  All of the trouble started about a month ago, and my investigation started by pulling this control system relay to test it.

[dbert]

What are the color bands on that diode?

Is it a 1N4102 8.7V 1/2 watt zener?  That would make sense for the circuit.

I initially thought that it was the same as the ABS relay used by BMW in that era, but it does appear to have a different purpose.

You mean the one hiding underneath the coil?  I can hardly see anything under there.

[strawberry]

with zener diode you can speed up relay (eevblog have some video about it) but I doubt that 1ms will do much here

about DO-35 diode. old style color bands. small signal switching diode 1N4448 equivalent to 1N4148
sometimes single band 1N4448 (yellow) and 1N4148 (black)
1N4448 5uA leakage
1N4148 50uA leakage

[DBecker]

What are the color bands on that diode?

Is it a 1N4102 8.7V 1/2 watt zener?  That would make sense for the circuit.

I initially thought that it was the same as the ABS relay used by BMW in that era, but it does appear to have a different purpose.

You mean the one hiding underneath the coil?  I can hardly see anything under there.

Perhaps I'm missing a reason for the confusion.  This appears to be a simple low and reverse voltage lockout relay as was typical for ABS units of the era.

The three diodes are a glass 1N4102 8.7V zener for low voltage drop-out, a glass small signal blocking diode (probably 1N4148) for reverse voltage lockout, and a larger epoxy 1N400x type for the coil kick-back.

Measure the resistance of the coil directly on the leads at circuit board, not adjacent on the traces, to verify that it has actually failed.  My guess is that there is just a cracked solder joint from heat, vibration and age.

[bdunham7]

The +12V on pin 85 is present only when the key is turned to the "run" position.  This is not during cranking, but when  all the dash lights and radio come on.  Then when you turn the key to crank the engine (start position), the voltage is NOT present.  When the engine starts and you release the key, it goes back to +12V.

That would indicate that the operation of the relay is not reversed as suggested earlier, but rather that it operates just like any other relay.  With, of course, the usual disclaimer "unless something weird is going on".  That would leave me baffled as to why they used a transistor pre-relay since the coil current would not be an issue for the ignition switch.  Before pulling the relay, did you confirm its operation directly with a meter or test light?

I'll look again to see if there's anything that would be likely to cause your 'reverse' operation.  As for the pump running with the car off, I'm not entirely sure some of these didn't do that by design, but unless I missed something in the wiring diagram, your example shouldn't.  A long time ago I made a tester for these Bosch-pattern relays so that you could see what all 4 legs were doing (hot, grounded, open) at one time with red/green LEDs.  I'll try and dig it up.  Where are you located b/t/w?

I don't see a problem jumping 30 to 87, nor do I see a problem temporarily swapping in a more normal Bosch relay for 75e.  It does bother me that there appears to be no fuse in the circuit feeding 75e.  How large are the wires going to it?

[DBecker]

The +12V on pin 85 is present only when the key is turned to the "run" position.  This is not during cranking, but when  all the dash lights and radio come on.  Then when you turn the key to crank the engine (start position), the voltage is NOT present.  When the engine starts and you release the key, it goes back to +12V.

That would indicate that the operation of the relay is not reversed as suggested earlier, but rather that it operates just like any other relay.  With, of course, the usual disclaimer "unless something weird is going on".  That would leave me baffled as to why they used a transistor pre-relay since the coil current would not be an issue for the ignition switch.  Before pulling the relay, did you confirm its operation directly with a meter or test light?

I'll look again to see if there's anything that would be likely to cause your 'reverse' operation.  As for the pump running with the car off, I'm not entirely sure some of these didn't do that by design, but unless I missed something in the wiring diagram, your example shouldn't.  A long time ago I made a tester for these Bosch-pattern relays so that you could see what all 4 legs were doing (hot, grounded, open) at one time with red/green LEDs.  I'll try and dig it up.  Where are you located b/t/w?

I don't see a problem jumping 30 to 87, nor do I see a problem temporarily swapping in a more normal Bosch relay for 75e.  It does bother me that there appears to be no fuse in the circuit feeding 75e.  How large are the wires going to it?

The transistor amplifier is needed because of the zener diode used for brown-out protection.  The relay can use a small, 1/2 watt zener and a small signal diode while using a common 12V coil.  They made the module self-contained and packaged like a standard relay for easy replacement.

The low and reverse voltage relay powered and protected the expensive ABS control module and sometime pump motor.  They could operate on full battery voltage, without a series diode.  The ABS module probably has a shunt diode for transient protection, but would immediately burn out if a battery was installed backwards or a jump start went bad.

The BMW equivalent had a fuse wire and reverse diode inside the protection relay case.  It was common for the fuse to burn "for no reason", along with plenty of times when it blew for an obvious/admitted reason.

[dbert]

I'll look again to see if there's anything that would be likely to cause your 'reverse' operation.  As for the pump running with the car off, I'm not entirely sure some of these didn't do that by design, but unless I missed something in the wiring diagram, your example shouldn't.  A long time ago I made a tester for these Bosch-pattern relays so that you could see what all 4 legs were doing (hot, grounded, open) at one time with red/green LEDs.  I'll try and dig it up.  Where are you located b/t/w?

I don't see a problem jumping 30 to 87, nor do I see a problem temporarily swapping in a more normal Bosch relay for 75e.  It does bother me that there appears to be no fuse in the circuit feeding 75e.  How large are the wires going to it?

I'm in Castle Rock, CO just south of Denver.

I'll put a jumper in there to see what happens.  Most of the wire sizes are indicated on the wiring diagram, shown in cross-sectional area.  For instance, the ground wire connected to 86 is shown as 2.5 N, which means a black wire (Nero in Italian) that is 2.5 mm².  When there is no wire size indicated, it means 0.5 mm² by default.

The equivalent AWG sizes are:

85 - 24 awg
86 - 10 awg
87 - 24 awg
30 - 24 awg

My transistors from Digikey are stuck in a postal service loop and doesn't look I'll get them for a couple more days.  When I do, I'll pop one in and re-flow all the solder joints.  Then I'll measure coil resistance.

[floobydust]

They're the male spade terminals on the back of the ignition switch.
30 - constant hot from battery
15 - accessories, hot when key in run position
50 - connected to the starter, hot when key in start position
P - not used in the 1989 model year
R - supplies the ABS system, hot with key in run position only

Note this relay defaults to always on (for safety) and the control line shuts it OFF when +12V power is applied to 85.
So on a workbench connecting 12V power across 30(+) and 86(-) the relay should always clank and pull in. Then connecting (+) power to 85 should make the coil release. The extra transistor and all the drama is to invert the relay's operation.

I'm confused by this.  Are you talking about the relay I'm having trouble with, 75e?  Are you saying that this thing is supposed to have the contact normally closed, and opens up when it receives voltage from the ignition switch on 85?  That would seem backward to me.  It would mean power is supplied downstream only when the key is off, right?

Yes, I'm confused too. Looking at your 75e relay pictures the transistor (thus the coil) are normally on. Control terminal 85 must be at +12V for the transistor (=relay) to turn off. But the relay is powered from the vehicle battery, which means 85 must be up all the time when the key is off. Keeping 12V at terminal 85 gives a small parasite drain of 4.4mA
The ignition switch R terminal (to 75e control) looks to be hot in key off? The pic shows the black wiper conducting nothing to R when the key is on, which fits my theory.

I thought Ferrari might be a bit sinister and disable the ABS if the anti-theft is activated lol, no brakes for you! Although I have driven muscle cars through brake failures and jammed throttles, quite the hair raiser.
Did you do anything to the ignition switch as far as replacements etc. ?

[...] By the way, thanks for combining the two halves of the diagram.  I'm curious how you did that while also making the whole thing a little less fuzzy.  That helps a lot!

It was too hard to read the wiring diagram split in two. From the original scans I imported those two pages and joined as one page, and increased the black level/contrast. Not an expert but use GIMP sometimes difficult to learn and use, but it's free and powerful.

[dbert]

Nope, terminal R on the ignition switch is hot only when the key is "on", and turns off during engine start.

I will also mention that I've been in touch with other owners of the 89 328, and they all say that their brake pump only runs after they turn the ignition on.  I wish I could coax them to pull their relays and test the function, but they're all aware of my problem and are scared to touch it. 

On the ignition switch drawing, that rectangular switch is the switch that activates a warning buzzer to let you know that you left the key in the ignition when the door is open.  It has no other function.

[floobydust]

This is good, there is a mistake somewhere     The board's diodes are not making sense, it sure looks like one is installed backwards.

D1 (black) diode could not be a zener as that would blow the transistor in reverse-current (no base resistor).
D2 as a zener would require its cathode connected to the base.
D3 (across coil) has the band going to ground...
edit: only makes sense if the fat yellow band is the cathode (not the gray band) and they are not zeners.

[floobydust]

Nope, terminal R on the ignition switch is hot only when the key is "on", and turns off during engine start.

I will also mention that I've been in touch with other owners of the 89 328, and they all say that their brake pump only runs after they turn the ignition on.  I wish I could coax them to pull their relays and test the function, but they're all aware of my problem and are scared to touch it. 

On the ignition switch drawing, that rectangular switch is the switch that activates a warning buzzer to let you know that you left the key in the ignition when the door is open.  It has no other function.

Any chance the Italamec 493 relay is the wrong one for that position 75e? From the pics and the module's design, it's working as it should - backwards. From your notes, 75e pin 85 gets power during engine run (relay off) and interrupted (relay on) during cranking or key off. That's the opposite isn't it? I kind of suspect a factory documentation error or modification TBH.
I would ask other 328 owners for a picture of that place on the relay panel to see if a type 493 is actually there.

[dbert]

It's definitely the correct relay for that spot.  Here is the page for it at one of the big parts suppliers - https://ferrparts.com/parts/Ferrari/62567200

Ferrari documentation of the era is known to have numerous errors.  I know of a few places in the wiring diagrams that are not correct.  Ferrari was a tiny niche manufacturer in the 80's and they weren't very meticulous about documentation.  They often made changes "on the fly" due to occasional parts shortages, substituting whatever they had on the shelf at the moment, so it isn't uncommon to see differences in one car vs the next one on the assembly line.  For all we know they may have used this particular relay just because they had a box full of them and the regular relay was out of stock on that particular day of the week, and Luigi said "well this box of relays over here ought to work in this application, let's just use them."  Porsche did the same thing.

But if this relay is supposed to work backwards (normally closed, opens on input), then it makes absolutely no sense.  According to the wiring diagrams and the connections between the relays, it would mean that the pump can run ONLY when the engine is off or during cranking.  That is not how it is supposed to work and opposite to how the other 89 cars are working.

My transistors are being delivered today so I can install one later and reflow the joints and see what we get.  I'm also going to try a jumper in that position.  I'm expecting that with the jumper the pump should run anytime the pressure switch calls for it, regardless of key position.  I'll report back later with my results.

[dbert]

Well, I'm happy to report that the jumpering (jumping?) of 30 to 87 caused the pump to run whenever the pressure switch told it to.  So, I think that confirms that the relay in that 75e position needs to work like a typical relay, not backwards.

And I'm sad to report that my short drive began with a rear tire sidewall blowout.  Sounded like an explosion.  I had to order a new tire and will take a week to get it.  I was going to try a panic stop to see if the ABS kicked in, but I didn't get that far.

I ordered some new relays, with flyback diodes in them.  Two normally open and two normally closed (just in case).  At $2.50 a pop, why not.

[dbert]

Oh, and did you guys notice the solder bridge?  I haven't touched any solder connections yet.  I think that bridge is to a mounting post for the coil assembly that isn't supposed to be part of the circuit.

[floobydust]

Are the original relay contacts N.C. or N.O. ? I did not see the a pic of the contacts.

[jonpaul]

check for corrosion on connectors, cold PCB to relay solder joints, relay coil winding broken at terminals or PCB pins

jon

[dbert]

Are the original relay contacts N.C. or N.O. ? I did not see the a pic of the contacts.

At the moment, the contact is open so I assume it always was.  I have to push it with my finger to close it.  And after installing the new transistor and re-flowing the whole board, there is still no action from energizing the coil.  Resistance across the coil is on the order of 11k ohms.  I can get continuity between 30 and 87 only by pushing the contact closed.

[bdunham7]

Resistance across the coil is on the order of 11k ohms.  I can get continuity between 30 and 87 only by pushing the contact closed.

11K is way too high for that type of design, it is probably open and you are measuring some leakage thru your other components.  A new, standard N.O. relay will probably fix all this (albeit without the low voltage protection function).   I have no idea why your pump would run with the ignition OFF. 

[dbert]

I have no idea why your pump would run with the ignition OFF.

Nor do I, but I'm ready to shrug my shoulders and move on.  I'll let you guys know how the new relay works.  Here's the one I bought:

https://www.digikey.com/en/products/detail/cit-relay-and-switch/A21ASQ12VDC1-6D/12503356

It does have a diode across the coil for circuit protection.

[dbert]

Hi all, I finally got the new relay in and all is working as it should again.

Big thanks to all of you who contributed!  Much appreciated!

[floobydust]

So the transistor stuff is gone? It's strange that something was inverting things.
Also, the relay inside of the old module is a standard form factor, so it was possible to replace.

[dbert]

Yep, the new relay only has a single diode across the coil, no other stuff in the box.  I had to swap the 85/86 female spades in the relay sockets to respect the diode's polarity (cuz they were originally backward from standard), but the pump is coming on when it should, and not when it shouldn't.  All fixed now!

[Jeff eelcr]

Good, the origainal relay looks like a european open-frame relay PCB mount
used by most european car manufactures.
Jeff