'93 240 AMM

  • Thread starter Thread starter Chuck Fiedler
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Chuck Fiedler

Does the computer on a '93 249\0 send a code indicating an AMM
failure? What is it? If not, how do you know that the AMM needs to be
replaced?

Chuck Fiedler
Nothing but Volvo since 1974
 
Chuck Fiedler said:
Does the computer on a '93 249\0 send a code indicating an AMM
failure? What is it? If not, how do you know that the AMM needs to be
replaced?

Chuck Fiedler
Nothing but Volvo since 1974
Click to expand...


Usually the car won't start. You unplug the AMM and it starts up, that tells
you the AMM is bad.

As far as I know, the AMM puts out an analog voltage proportional to the air
flow, so if you can find the pinout, you should be able to apply power, then
monitor the voltage while blowing air through it.
 
:
:
: : > Does the computer on a '93 249\0 send a code indicating an AMM
: > failure? What is it? If not, how do you know that the AMM needs to be
: > replaced?
: >
: > Chuck Fiedler
: > Nothing but Volvo since 1974
:
:
: Usually the car won't start. You unplug the AMM and it starts up, that
tells
: you the AMM is bad.
:
: As far as I know, the AMM puts out an analog voltage proportional to the
air
: flow, so if you can find the pinout, you should be able to apply power,
then
: monitor the voltage while blowing air through it.


Hi James,

You said: "You unplug the AMM and it starts up, that tells
you the AMM is bad."

When our '93 245 failed to start I unplugged the AMM and the engine started
(in "limp mode"), but I didn't scrap the AMM. I plugged it in and out ten
times (on the earlier advice of a friendly Volvo dealership tech........
The magic number seems to be "ten" :-). The engine started and ran
normally, and has done so ever since. When I got home I cleaned the plug
and socket with Contact Cleaner then liberally applied Dielectric Grease to
both.

I recommend that all owners give the AMM this treatment without waiting for
trouble.

Andy I. ('58 445 wagon; '65 122S wagon; '67 121 direct import; '74 145; '74
142; '86 245; '93 245 Classic; '97 855 AWD turbo.)
 
on my 89 240 wagon, I found that the little metal "fingers" in the AMM
connector were making poor contact, so I GENTLY pushed them toward the
centerline of the connector, using a thin probe. I also sprayed with contact
cleaner as previously mentioned. Has been working fine for the last 2 years!

note the emphasis on the word GENTLY!!!
 
Speaking of AMM on a 240, if you wish to destroy it, then don't change
your air filter after 6 months. It cost me TWO AMM because I forgot
to change the air filter after 6 months on two occasions. And at
~$400, it's not fun!

If you do the same mistake than me, you can use contact cleaner and
spay inside the AMM. It will extend the life by a few months. You
might have to spay it every 3-4 weeks. Best advice I can give you,
CHANGE YOUR AIR FILTER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
Someone said:
Speaking of AMM on a 240, if you wish to destroy it, then don't change
your air filter after 6 months. It cost me TWO AMM because I forgot
to change the air filter after 6 months on two occasions. And at
~$400, it's not fun!

If you do the same mistake than me, you can use contact cleaner and
spay inside the AMM. It will extend the life by a few months. You
might have to spay it every 3-4 weeks. Best advice I can give you,
CHANGE YOUR AIR FILTER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Click to expand...


How did the air filter damage the AMM? I usually change mine every 5 years
or 50K miles, have yet to ever lose an AMM.

Now a bad airbox thermostat certainly will, I live in a mild climate so I
just rip out that whole air preheat system.
 
WOW! Every 50K miles????????

Apparently, because I did not change the filter after 6 months (
travel ~ 10K), the AMM died. Happened to me twice!!! Within 18
months.

Since then, it was 6 years ago, I have changed the air filter
religiously every 6 months and AMM is going strong.

It is unlikely that two new AMM could have been defective. Though
possible, it is not likely.

The second AMM is the one I decided to spray contact cleaner right
inside the AMM and managed to get about 3-4 additional months out of
it.

Hope it helps.
 
Someone said:
WOW! Every 50K miles????????

Apparently, because I did not change the filter after 6 months (
travel ~ 10K), the AMM died. Happened to me twice!!! Within 18
months.
Click to expand...


I don't know how that's even possible. At worst a dirty air filter will
restrict flow and cause a loss of power. The 4 cylinder Volvos have massive
filters, at least double the surface area of any other car I've worked on.
Could be the air out here is unusually clean, I dunno, but even at 50K it
didn't look too filthy and I didn't notice any performance change when I
replaced it. Car has over 290K on it, I don't know if the AMM has ever been
replaced, I've never done it.

Do check the wax thermostat and preheat valve in the airbox though, those do
fail, and a stuck open flap most certainly will kill the AMM.
 
After 6 months, my air filter is quite dirty. I drive though a new
development where they are still building houses and in summer, with
the wind, you can see the dust passing you by.
 
In my Bentley manual it has a test for the AMM, put a ohmmeter across two of
the contacts, should be reasonably close to 108ohm. I'd get the boock to
check for sure but it's in the garage and I'd have to go outside and it's 35
degrees....
IIRC, the self-test module will give a code for a FUBAR AMM, yes?
mkl
 
Mike Lenker said:
In my Bentley manual it has a test for the AMM, put a ohmmeter across two
of the contacts, should be reasonably close to 108ohm. I'd get the boock
to check for sure but it's in the garage and I'd have to go outside and
it's 35 degrees....
IIRC, the self-test module will give a code for a FUBAR AMM, yes?
mkl
Click to expand...


That will tell you if the hot wire is intact, but all the real world AMM
failures I've seen have been something else.
 
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