'93 240 AMM

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.

: > 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

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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.

H>

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

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