Hello:

I decided to start a new thread on this. I'd indicated an issue with
my 1993 240 DL Wagon and that I had tested the AMM.

A few respondents indicated that the ONLY way to test was to replace
it with a known good or new unit--and on that I must respectfully
disagree. If an AMM does not pass the tests below,  chances are it
must be replaced.

I'll outline the procedure for testing an AMM below--but do keep in
mind this generally relates to those on 240's built between 1988 and
1993.

I base this on the Hayne's Manual, Bentley manual and also years of
experience with Volvos--and an inquiring mind.

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Scope of Test: Test is performed without removing AMM

Tools required:  Hand and fingers to remove plug from AMM, a basic VOM
(Volt Ohmmeter-- digital (DVOM)  or otherwise.

Note: this test is only valid for the following LH injection systems:

LH 2.0. 2.2 and 2.4

We shall be testing the following:

Platinum heated wire

Idle mixture pot (potentiometer)

Burn-off function

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Begin test:

With ignition off, disconnect connector from AMM.

On LH 2.0 systems connect an Ohmmeter between terminals 6 and 7 on the
AMM.

On LH 2.2 and 2.4 connect between terminals 2 and 3.

At ambient temperature (in other words,  not in my garage in January)
the AMM platinum wire resistance should be:

LH 2.0 or 2.2: 3.5 to 4 Ohms
LH 2.4 : 2.5 to 4 Ohms

Step Two:

Idle Mixture Pot...

LH 2.0    Connect DVOM to terminals 6 and 12 on the AMM

LH 2.2    Connect to terminals 2 and 6

Compare ranges, but it should be within 0 to 1,000 Ohms

If not within those specs the  AMM is bad and needs replacement.

Step Three:

Burn-off function

This is basically what keeps the platinum wire on tha AMM clean after
the engine is running.

In this case--and for this test-- the engine must be running. Pull
back the rubber boot on the AMM connector.

Connect a VOM (voltmeter) between terminal 4 on the AMM and ground.

Run engine to 2400 or 2500 RPM, let it get back to an easy idle and
then shut down.

Wait for 3 to 5 seconds and then check voltage. The voltmeter should
show at least some sort of voltage for a second or so.

If not the AMM is likely kissed and should be replaced.

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End of test procedure

I'd be grateful if anyone can offer better testing procedures but have
not found one yet.

Regards,

Doc