Has anyone successfully repaired a a transmission pressure switch?

[jedwards]

Just wondering if anyone has ever successfully repaired or re-activated the transmission pressure switch that triggers the Constant Speed solenoid?  Both mine seem to have failed with little warning, which is odd, but at around 200 Euros each and several weeks to get replacements units  to Australia at this time of year, I was hopping there mint be some fix that would allow me to enjoyer the car over the Christmas  break.
if they can be cleaned out and and made functional or even replaced by one of the thousands of oil pressure switches using in other lesser brands, I'd love to know if there is anything that might be made to work.

[ctaylor738]

I believe that you could replace the pressure switches with a five pole (30, 85, 86, 87, 87a) relay driven by the neutral safety switch.  Will provide details if anyone is interested.

[jedwards]

Yes details would be great thanks

[ctaylor738]

It's a bit more involved than I initially thought.  It needs two new relays and a bit of rewiring.  See attached diagram.  Fusing not shown.

The way (I think) it would work is:

- when Neutral Switch is in P or N, Relay 2 is powered, 87a cuts off, so no ground to the CSS.
- when Neutral Switch in other positions, the CSS gets ground from 87a via 30.
- when the key is turned to Start and the Neutral Switch is in P/N the starter circuit (50) is powered.

The relays are less than $10 apiece.

Cheers,

[wwheeler]

Seems odd that both would go out at the same time. One is for reverse and the other drive. Assuming no contamination from trans fluid which would effect both, the drive would normally go out first simply from more use. Have you done any kind of electrical troubleshooting to see if it is something else down the line?

[jedwards]

I agree, losing both did seem odd to me as well, however  I have not done any wiring work lately so don't believe there this is a self induced problem. The fuel pump does seem a little noisy of late ( I have an after market in-line fuel pump fitted) and I had wondered if that could be drawing more current and limiting supply  of the current to the switches.

[wwheeler]

There are many connections from the switches to the actual solenoid that could be at fault. Might want to check if you are getting a ground to the solenoid from the switches if you haven't already. Have you tested the solenoid itself? It is possible I guess if your trans fluid is low, internal trans pressure is too low to activate switches. I am not a transmission expert by any means. You can also run a test wire to the switches and check they are grounding when the trans is in R or D.