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Joe, Technician
Category: Car
Satisfied Customers: 722
Experience:  27 years import and domestic auto repair.
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1999 mercury grand marquis: windshield wipers..whats wrong..fuse,relay

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i have a 1999 mercury grand marquis,the windshield wipers only work when they are on fast.not slow or whats it the fuse,relay,or motor?and how do i fix it on a very low budget at the moment

HelloCustomer The most common wiper failure on you mercury is the wiper control module. This is uisually the problem when you loose intermittent and/or a high or low speed. This part is only available from the dealer, and is approx. $150.00graphicgraphic

Customer: replied 8 years ago.
that would be most likely whats wrong?because other people already told me that.and i dont understand how the fast would still work and none of the other speeds if the module is couldnt be a relay or something cheaper?and if it is that how hard would it be for me to replace?

The module has multiple circuits, or switches built into it that control the high/low and intermittent speeds. If one of these circuits goes bad, you will loose only that one function of the wipers.

As you can see from the diagram I sent you, this system does not use a relay, the control module functions as the relay. It is fed power through one 30 amp fuse, and if the fuse was blown, you would have no wipers at all.

The only other component in the wiper system is the switch, and a failure of this type is not typical of the switch. I have dealt with this problem several times and it is always the control module.

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