1979-1993 & 94 Conv [Subscribe to Daily Digest] |
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Finally got it running. It was a weird problem. The typical stuff was fine - fuses and relays all tested good in another convertible (tested them myself), ebrake on and switch was working, roof switch tested good, battery good, relays clicked when switch was on, but the pump motor would not run. I connected a battery to the pump directly and it ran great. A test light showed power all the way to the relays, but not to the motor. The connector between the relays and the motor also did not receive power. However, the relays clicked. Grounds around the back-seat relay box were fine, connections below the relays were fine, fuse back there was fine, everything seemed fine and ready to work. Except no power to the pump.
After pouring over the wiring diagram in the Bentley manual, I found that there are two separate power systems going to the 2 pump relays under the back seat. One power supply goes through the roof switch and runs the electro magnets inside the relays. That worked since the relays were clicking and the test light showed they were powered (the wire between the switch and the relays). There was another power source - a large white wire (violet in the Bentley, pin 87 under the relays) that went directly from the car battery through the 2 fuses and straight back to the relays. THAT was not getting power. Power was good through the distribution box and through the fuses and connector, but did not make it to the relays. AND the relays still clicked even when the fuses were removed. So I figured it must be a separate system and there would have to be a short where that wire goes through the firewall or thereabouts.
To test, I connected a thick Y-shaped wire to the connector just downstream of the fuses, ran it through the open passenger-side window, and stuck the two other ends into pin 87 under both pump relays under the rear seat. Then said a quick prayer so-as not to start the car on fire, started the car, and hit the switch. BINGO. The pump worked and the top went up and down as if nothing had ever happened.
So moral of the story - if everything is good but the pump still won't run (but it does run when connected straight to a battery), check the wiring diagram. There are two separate power sources running the relays.
posted by 67.2.108...
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