Author Topic: No tach, oil light on (Read 4864 times)

Spydr26 · « **on:** March 18, 2005, 07:33:03 pm »

So for the last week or so my oil light would flash and my tach wouldn't work when I started the car, but when I acclerated it would begin working. Today the tach doesn't work at all, and the oil light flashes all the time now. I've checked the oil and I'm full, and it looks like oil is getting to the top of the motor. So my question is the sensor for the tach the same as the oil light? does anyone know where it is? or do I have a more serious problem? Oh and my car is a 94 td golf. Thaks for the help.

QuickTD · « **Reply #1 on:** March 18, 2005, 09:26:33 pm »

Your alternator is shot. The alternator provides the signal for the tach. It also supplies the speed signal for the dynamic oil pressure warning system. This system uses 2 oil pressure sensors. One sensor is used at low engine speeds (below 2000rpm) and will turn on the oil light at pressures below 7psi. The other oil pressure sensor comes into play at 2000rpm and will turn on the light at less than ~20psi. Without the speed sense signal from the alternator the dynamic oil pressure warning will malfunction.

The alternator can probably be rebuilt. Because the problem came on over the course of a few days, it sounds like the brushes just wore out. You might be able to get a regulator/brush assembly from your local auto electric supply.

Spydr26 · « **Reply #2 on:** March 18, 2005, 11:01:32 pm »

If the alternator is shot then why hasn't my battery died?

WishIHadaRabit · « **Reply #3 on:** March 19, 2005, 03:01:23 am »

Same thing happened to me. Its not the alternator its the wiring. My wires where broken just after the plug at the alternator (inside the plastic sleeve).

If you keep driving with the return wire malfunctioning you will burn-out your alternator.

Hammy · « **Reply #4 on:** March 19, 2005, 10:36:22 am »

Quote from: "Spydr26"

If the alternator is shot then why hasn't my battery died?

They are two separate feeds. The tach signal comes from the 'W' terminal. The battery is charged off of the field connection.

I would check and clean connections at the alternator. Also look at the condition of the wire itself, since it is old. Then I would probably bet on the alt being shot.

Patrick · « **Reply #5 on:** March 19, 2005, 11:44:31 am »

A worn or loose alternator belt can give you the same symptoms......