connector on MAF
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From: Hotlanta - NE of the Perimeter
Hmmm...
Guess he didn't read the tips section. In particular this one-
6. When asking a question always state: year/model/auto or manual, and be as specific as you can.
We're here to help...but we gotta know the model years!
Guess he didn't read the tips section. In particular this one-
6. When asking a question always state: year/model/auto or manual, and be as specific as you can.
We're here to help...but we gotta know the model years!
Three Wheelin'
Joined: Jan 2002
Posts: 1,560
Likes: 2
From: Maryland
Chris,
The test plan book shows the interconnect of the MAF to the LH control unit, but does not describe purpose of each pin other than stating that "it is possible to check positive and ground activation on terminals 4 and 2 of a disconnected hot wire plug air sensor plug. Connect volt meter to terminals 4 and 2 and bridge terminals 30 and 87 in relay XXV"
BTW, schematic shows 4 being ground. the other pins are just labled "hot wire control" (lot's of help there!).
If I find anything more descript, I'll let you know.
Greg
The test plan book shows the interconnect of the MAF to the LH control unit, but does not describe purpose of each pin other than stating that "it is possible to check positive and ground activation on terminals 4 and 2 of a disconnected hot wire plug air sensor plug. Connect volt meter to terminals 4 and 2 and bridge terminals 30 and 87 in relay XXV"
BTW, schematic shows 4 being ground. the other pins are just labled "hot wire control" (lot's of help there!).
If I find anything more descript, I'll let you know.
Greg
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Joined: Feb 2002
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From: Cambridge England
Chris,
The connections are:
pin1 burn off +ve volts to activate
pin2 +12v from relay
pin3 ground from/to LH brain
pin4 ground, connected to metalwork of MAF
pin5 output to LH
pin6 idle mixture pot (when used) depends on model year
The same Bosch MAF was used on all 928 models, some use the internal pot, others an external. those with a cat don't use any pot.
Hope this helps ?
John '86 S2 Euro , Cambridge England.
The connections are:
pin1 burn off +ve volts to activate
pin2 +12v from relay
pin3 ground from/to LH brain
pin4 ground, connected to metalwork of MAF
pin5 output to LH
pin6 idle mixture pot (when used) depends on model year
The same Bosch MAF was used on all 928 models, some use the internal pot, others an external. those with a cat don't use any pot.
Hope this helps ?
John '86 S2 Euro , Cambridge England.
Three Wheelin'
Joined: May 2001
Posts: 1,641
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From: Hudson Valley NY
Terminals 3 and 6 = 0 to 1000 ohms (CO Potentiometer)
Terminals 3 and 5 = 3.6 to 4.1 ohms (hot-wire electronic circuit)
Plug connected, key on back probe terminal 3 and 5 = 1 to 5Volts (hot wire signal). With a blow dryer, blowing though the hot wire = voltage rise with terminals 30 and 87 of the LH relay jumped. Never use a wire as the manual illustrates, make a jumper with an inline fuse holder (use a 15amp. Fuse, real world testing)
The most common failure is the hot wire itself; with repeated heating and cooling the heating filament can fail.
TEST. Burn off cycle. The engine must be hot, above 140 degrees. Remove the cover and the filter; rev the engine above 2000 RPM’s. Shut the engine off, after a time delay of 4 sec, the hot wire should be glowing red.
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
Terminals 3 and 5 = 3.6 to 4.1 ohms (hot-wire electronic circuit)
Plug connected, key on back probe terminal 3 and 5 = 1 to 5Volts (hot wire signal). With a blow dryer, blowing though the hot wire = voltage rise with terminals 30 and 87 of the LH relay jumped. Never use a wire as the manual illustrates, make a jumper with an inline fuse holder (use a 15amp. Fuse, real world testing)
The most common failure is the hot wire itself; with repeated heating and cooling the heating filament can fail.
TEST. Burn off cycle. The engine must be hot, above 140 degrees. Remove the cover and the filter; rev the engine above 2000 RPM’s. Shut the engine off, after a time delay of 4 sec, the hot wire should be glowing red.
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
Thread Starter
Racer
Joined: Jun 2002
Posts: 265
Likes: 0
From: ventura ca
this really helps. thanks guys.
is there pictures of the pot anywhere. I think mine has one. It has an externally adjustable allen head screw down a little ways inside a boss on the side. My car also has a cat?
is there pictures of the pot anywhere. I think mine has one. It has an externally adjustable allen head screw down a little ways inside a boss on the side. My car also has a cat?
Rennlist Member
Joined: Feb 2002
Posts: 7,059
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From: Cambridge England
Chris,
The pot isn't connected on your car if it has a cat. It is on the MAF, 'cos they used the same Bosch part on all 928's. The cat works with the O2 sensor in a closed loop and the pot is therefore redundant.
John
The pot isn't connected on your car if it has a cat. It is on the MAF, 'cos they used the same Bosch part on all 928's. The cat works with the O2 sensor in a closed loop and the pot is therefore redundant.
John