Hi all,
I've got a gremlin in my 86 240 DL. Let me first tell you that it occured this morning and I haven't really had the time to take a good look at connections or fuses because I had to get to work. Why don't these things ever happen on the weekend?

I went out to start the car this morning and there was barely enough power to turn over the engine. Yesterday it started right up. I pulled out a spare battery and jump started the car to get going. On the way to work I noticed the gas guage and speedo were not registering correctly. I know I had a full tank of gas and it only showed half full. I knew I was going about 70, but my indicated speed was 55-60. The upshift light never came on. Using the turn signals caused the speedo needle to waver. When it was safe enough to do so, I turned off the headlights and got higher readings on the gas and speedo and the upshift light started working. My temp gauge only works intermittently so I didn't watch it. All through this, the alternator idiot light never came on and it had worked in the past.

This doesn't look like an alternator or weak battery problem to me. About a week and a half ago, the ignition cut out on me at highway speed a couple of times and I think that was an indication of a short somewhere and today's situation looks to be the same. Any thoughts or advice as to where I should start to look for trouble would be appreciated.

Thanks,
Bert

looks like the alt brushes. Change them or resolder new ones in.

The faulty readings and the slow start does indicate a voltage problem.

If voltage is low, your gas gauge will read a closer to Empty.

My first thought ('86 car probably close to 200000 miles) is that the brushes in your alternator may be ready for changing. Or a very loose alternator belt.

The belt can be done quickly, The brushes can be done quickly too except you have to get the replacement brushes.

As Don says below, check your voltage coming off the battery when the car is running, see if the alternator is even trying to charge your battery.


--
'75 Jeep CJ5 345Hp ChevyPwr and two motorcycles: it wasn't Volvos safety , it was Longevity that sold me

"This doesn't look like an alternator or weak battery problem to me."

Actually, it does.

You need to make some measurements at the battery using a good DVM:

- A fully charged battery (engine off) should be 12.6 volts, or thereabouts.
- With the engine idling, battery charging, battery cold, around 14.5 volts, or so.
- As above, with battery warm, around 13.5 volts, more or less.

Much depends on the battery's condition, state of charge, temperature, other electrical loads, and so on.

Whether or not your problem is a bad alternator, bad ground, worn brushes, bad connection, bad regulator, or bad engine harness -- or a combination -- your symptoms sound very much like low system voltage.
--
Don Foster (near Cape Cod, MA)