1984 123 ACC Question

[250 LWB]

I have an 84 123 chassis with the Type 3 (horizontal pushbutton) ACC system. Something weird has been going on lately, and while I feel I understand these systems fairly well, this particular problem has me stumped:

When I put the system in any mode but "economy" everything works as expected. All vacuum signals and fans speeds are correct and change as conditions dictate. However, if I start out in "economy," I get nothing. It appears that the vacuum signals are correct, but I get no fan operation at all.

If I am in another mode and switch to "economy," the vacuum signals change as required and the fan continues to run for approximately 30-40 seconds, then it shuts off abruptly. Moving back to one of the other modes causes everything to resume normal operation.

I have resoldered the pushbutton controller (this is something I have done on a number of other MBs with similar systems) and found no difference in the operation.

The only other part of the system I can think might be affecting this is the fan controller (amplifier.) I eagerly await any suggestions or ideas that might help me resolve this problem.

Thanks!

Dan Penoff
Tampa, FL

[engatwork]

Welcome aboard.
I had the same problem with my '85 model and resolved it when I replaced the temperature controller module which is located behind/above the glovebox next to the fan controller module.l