P80 supplementary air system SAS Delete Diode part 1N4003

volvomadness · Post by **volvomadness** » 07 Dec 2017, 22:34

v70 1998. Since most all radio shacks are closed the 2161102 diodes are not available.

I can go to another electronics store but done know the specs of the diode.

Does anyone have the specs?

Thanks Madness

Post by **erikv11** » 07 Dec 2017, 22:56

The diode everyone uses has the generic part number 1N4003.

Take "1N4003 diode" to any electronics supply store, or mouser.com, or eBay, or Amazon etc. etc. and you will get what you need.

Post by **abscate** » 08 Dec 2017, 01:31

Modified title for search engine, thanks Erik!

The pop quiz question of the week is....

If the ECU just monitors a voltage drop to determine if the SAS pump is running, why do we use a diode across the terminals and not a resistor?

Employees of MVS, their relatives, and University Professors are not eligible to receive prizes.

Post by **jreed** » 08 Dec 2017, 05:17

The voltage drop caused by the resistor will depend linearly on current (Ohm's law), whereas the voltage drop caused by the diode is more or less constant (0.6V).

Post by **abscate** » 09 Dec 2017, 04:10

There's always one to ruin a good party. Some day I'll post the 12 valve challenge here for the quiz masters.

Jr nailed it, of course. It's much easier in electronics to compare voltages than currents, so circuit that detects the OXS voltage drop when the SAS works looks for a voltage drop after start.

The diode provides that drop regardless of the current flow in the circuit. We are lucky the Volvo engineers didn't decide to make the system test for low oxygen content, command SAS pump on, then look for high Content. That's what I would have done.

P

Post by **wizechatmgr** » 09 Dec 2017, 04:21

Zener diode?

Post by **abscate** » 09 Dec 2017, 04:36

No, she's a warrior princess and will never die.

I think it's just a silicon rectifier series if I remember my Horowitz and Hill

Post by **jreed** » 09 Dec 2017, 05:56

One option for those who have not yet installed their diodes, who can't find the 1N4003, is to use another diode in the 1N400x series. The main difference between the diodes is the maximum reverse blocking voltage rating listed below. All of them are rated for 1A forward current and should work fine in the application, though I've only tested the 1N4003.

Diode
1N4001 50V
1N4002 100V
1N4003 200V
1N4004 400V
1N4005 600V
1N4006 800V
1N4007 1000V

Post by **MrAl** » 09 Dec 2017, 06:36

Hi,

The diodes are 1N4001 through 1N4007 as noted.
They will probably all work the same because they are all almost the same except for the voltage that they will block which is higher for the higher numbers.
I doubt you would need the 200v version as the 1N4001 50v version would work fine at 12v reverse, but the price is usually the same of very similar for any of these so might as well get the higher voltage one 1N4003.

Any regular Si diode would probably work as long as the current rating is 1 amp or better. Since that one is said to work though, stick with that.

Schottkey diodes are another story. I would not get that because the forward voltage can be significantly lower.
Zener diodes are very different, dont get that either.
Dont think i would use a high speed diode either as the capacitance is lower and that may make a difference.
Would not use a lower current diode either like 1N4148 because that might blow out if a 1 amp diode really is required.

Post by **abscate** » 09 Aug 2020, 19:12

I’ve got 1000 of these from a cost reduction program on the Boeing 747 MAX SAFETY systems

Free to those who pm me and address with subject line SAS diode