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HELP!!! Randomly driving, when dash lights start illuminating, ac turns off, car starts bucking.. flooring it fixes it??

1309 Views 7 Replies 3 Participants Last post by  85_305
Ok. This is what has happened twice now since having the cc set on the highway.

First, the ac blower motor cuts WAY down, to barely trickling out the vents. I think the ac actually disengages too and just blows warm air.

Second, a few mins later the abs light illuminates.

Third, a few mins later the airbag light illuminates.

Fourth, the tach and speedo freezes at the speed they were travelling at.

Fifth, a few mins later the brake light starts blinking and chiming in the dash.

Sixth, a few seconds later the car starts losing power; it bucks in lower rpm's in the lower gears.



1999.5 5spd tdi, lots of mods... fmic, rc, 170k miles on car but 10k miles on FULLY rebuilt motor/clutch, stock turbo/sticks.

Any clues?

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Whenever you have weird electrical gremlins start with the obvious items: check that the battery terminals are clean & tight, then check that the ground under the battery tray is clean & tight. You could try replacing the Relay 109 and see what happens, it's a $10 part from idparts.com. http://www.idparts.com/catalog/product_info.php?products_id=350

Move on to the battery itself and the alternator. How old is the battery? If all of the connections are good, put a voltmeter across the battery terminals with the engine OFF and again with the engine RUNNING. You should have 12VDC with the engine off and somewhere around 14VDC with the engine running. If you have less than 12VDC with the car off, the battery may be bad. If you have less than 14VDC with the engine running, the alternator is probably bad. Any competent mechanic should be able to load test the electrical system.
Battery and belt/pulleys, grounds etc seem ok. Where is this ground under the battery tray? I'll try that one.

Is there a way to diagnose the relay 109? What does relay 109 do?

I'll try running a voltmeter across the battery. Thanks man:thumbup:
There's no way to test the relay that I know off. Relay 109 controls the main power supply to the ECU, so when it gets flakey, all sorts of weird things happen. Since it's so inexpensive, most people just replace it. If you've never changed it in the past, it might be worth the $10.

For the main ground just follow the negative cable to where it attaches to the chassis. You may need to remove the battery and tray to get really good access to clean it up.
Ign switch

Try moving your key in ignition switch, jiggle it back and forth a little.
my 98 tdi had some of the same problems. It was the switch bounching
off contacts.
Well I found out that i can just push the clutch in and rev it to 3k+ to get everything working again. As soon as I see the abs light come on I just rev it to 3k+ and everything works fine. It's really irritating though :irk:
Is there any screeching? It sounds like an alternator/regulator problem. The alternator pulley is a clutched pulley. It could be getting ready to fail.

Do you have a voltmeter to test the system volatge with while off/running?
Nope no screeching/squeeling at all. The belt looks great, and so do the pulleys. As soon as I rev it up though, it's good the rest of that trip. Its weird.
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