http://www.modulemaster.com), which tests and repairs them. They said they found some problems, and repaired the module. They believe it should work fine now.
(3) The idle switch on the throttle has been repaired and adjusted, and seems to work fine now.
(4) I tested the following inputs on the idle control module connector, with the following results:
K - A/C. Tested OK: 0V when A/C off, +12V when A/C on.
31 - Ground. Tested OK: grounded.
ST1 & ST2 - Idle valve control. Tested for continuity to valve's connector: OK.
LS - Throttle switch. Tested OK: grounded at idle and max throttle, open otherwise.
T - Engine coolant temperature sensor. With the engine warm, there was about 250 ohms between this and ground. I'm not sure if that's appropriate or not.
LH - Power steering pressure switch. Should be grounded when steering wheel is turned all the way either direction, but I didn't test it.
15 - Power. Tested OK: +14V when engine running.
50 - Start. Should be +12V when ignition key turned to "start", 0V otherwise. Tested OK.
1 - Hall generator, Digifant, and/or ignition coil, I think. When engine running, it appears to fluctuate rapidly between about +8V and +12V. I don't really know what it's supposed to do, or what it's for.
(5) When the van is running, I get a signal of between 600 Hz and 1300 Hz at the idle valve connector. Frequency seems to vary with different load (A/C, steering, etc.), but not always consistently. But that may just be a limitation in the test equipment (a multimeter with a frequency input), since my understanding is that the idle control module doesn't change the frequency of the signal, but rather the width of the "on" portion of the pulse.
(6) If I remove the idle valve from the van, and apply a straight 12V to it, the piston jumps to its limit.
(7) In the van, with the engine running, under various throttle settings and loads (A/C, etc.), the idle valve piston never moves - it always stays closed. The valve never vibrates or makes any sound. Most literature I've read says the valve should hum and vibrate, but I've seen some comments suggesting that some don't, but work fine.
(8) Module Master sent me a video showing an idle valve being tested. The piston moves as the frequency (or pulse width) of the input changes.
(9) My idle with no load is about 800-900 RPM.
(10) Engine will die at idle if I turn on the A/C with a fan speed above 2 (or sometimes at 2 or 1). It will also usually die if I turn the steering wheel to its limit.
(11) The incompetent shop says they are convinced that my problem is that the A/C blower fans are drawing too much current, and the alternator can't handle it, which is causing the engine to die. They replaced two perfectly good alternators based on a similar theory. Actually measuring the current draw was beyond their capability, so I showed it to them with my meter. The two blowers each draw about 4 amps at speed 1, 6 at 2, 11 at 3, and 14 at 4. That's about the same as the heater blower, which does not cause the problem. I also tried disconnecting one A/C blower, and that had no effect on the problem. So, the A/C blower fans don't seem to me to be the answer.
I figure these are all the possible causes for the problem:
(A) Bad idle valve. But: it reacts when hooked up to a battery, so it's at least not completely dead. Plus, it's new.
(B) Bad idle control module. But: it was just repaired, and supposedly tested OK by Module Master. It does put out some sort of pulsed signal to the idle valve.
(C) Bad connection between module and valve. But: seemed to me to test OK.
(D) Bad input to module. But: all the relevant inputs seemed to test OK to me, except that I don't know what #1 (Hall generator & ignition coil) should do, nor what T (temperature sensor) should read
I guess at this point I suspect (A), and I'm considering buying a known-working used idle valve to try, if I can find an inexpensive one.
Any suggestions for resolving the idle issue would be appreciated.
- Steven Sittser
