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I've got a 96 TD and just had a faulty CTIS gauge replaced. Now on inflation the rear needle rapidly "ticks" back and forth in the general range of the pressure.
The front gauge, however, doesn't do this. On inflation it ever so slowly increases to the preesure desired. This is much easier to read.
Before the gauge went bad, both worked like the front needle. Which way is correct?
About a year ago my gauge was giving false readings also. It turned out to be a small brass fitting about the size of a pencil eraser. The 2 lines from the compresser area to CTIS gauge (front-back) each should have this small part inline to eliminate the TICK-effect. In my case, one of these fittings was blocked. So the tech removed it and just put a small piece of tubing inline where the brass fitting had been. Said they'd order it. Never did. I could never find a part # for this fitting in the manual. Anybody know it? Works ok without it, except the faltering is annoying.
I believe that the newer trucks have a little damper located in line to the pressure gauge. Its sole function is to eliminate the rapid needle bouncing on the earlier trucks. If you look at the small plastic line leading from the CTIS solenoids (mine are red and black) you will see a little black plastic piece spliced in. It is about the size of a stack of 4 quarters or so. I'm simply guessing your mechanic failed to replace one of them when installing a new gauge. I would call the dealershp and see if they happen to have one laying around. Hope this helps,
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