Chrysler Repair: Power Brake motor running, brake fluid reservoir, chrysler town

Question
I know this is not in your list of expertise, but you list having repair manuals.

I have a 1993 Chrysler Town & Country minivan.  It has Power Anti-Lock brakes, that use an electric motor to build up pressure for application.  When you start the van you can hear the motor for a second or two as it builds the beginning pressure and then you will not hear it again until the brakes are applied and it must replace the used pressure.  The problem is the motor is running almost all the time.  It now shuts off for only a second or two then runs for a second or two, cycling constantly.  There has been no change in the stopping ability of the van.  If it wasn't for the fact of hearing the motor run, you could not tell anything was wrong.  The fluid level is fine, I find no leak.  Applying a gradual pressure with the van turned off will not allow the pedal to go down like that of a bad master cylinder.  I am questioning the integrety of the pressure switch it must have somewhere.  The van does have 190,000 plus miles.  I do not know what the switch would be called, nor where it is located.  I do see one mounted below and to the drivers side of the brake fluid reservoir.  Mounted in what looks to be part of the brake system.

I hope you can help.  Thanks for trying.  

Answer
Hi Cy,
I copied 8 sides and put them in the mail to you this afternoon. Thanks for the positive feedback. I think you can repair this yourself if you choose to.
Roland

Hi Cy,
By chance I have the '93 shop manual for the van which includes the anti-lock brake system. The motor you hear is powered by a relay that is mounted just in front of the driver side strut tower on a bracket. The relay is signaled to close by being grounded by a 'dual function pressure switch' mounted on the underside of the main box, the part of it that is underneath the domed pressure accumulator unit. (The 'dual' aspect of the switch is to keep the pressure within a certain range, and secondly to light the warning light if the pressure drops too far below the minimum for system operation). Access to the that switch is from underneath the van and requires a special socket tool (#6607) to properly grasp the switch for removal and for subsequent replacement and torqueing. The tool fits on the end of a normal extension bar.  The pressure in the system has to be released before replacing the pressure switch.
It may be that the pressure switch is o.k., but the relay is hanging up, which would of course then be a straight forward repair issue. The gray wire at the relay socket is the wire that when grounded by the dual pressure switch causes the pump to operate. So you could see with on ohmmeter if the that wire is in fact being grounded in synchrony with that of the pump operation or not, and if not then replace the relay.
Otherwise it looks like the dual function switch has to be replaced.
I can copy the pages that describe all this and send it by postal mail to you for your consideration. You could check out the switch and the availability of the tool from Chrysler or one of the automotive tool supply dealers. It is a Bendix unit so it should be widely available, but at what cost. There are two pressure sensors on the underside of the box, fore is the dual function switch, the taller one,and the aft is the boost pressure transducer.
So let me know if I can be of further help. I can easily xerox the pages and mail them.
Roland