I have a problem with my 1981 300TD that I will go through and try to pin down in the morning but I am hoping someone else may have had the same problem and can give me an idea where to start.
When I left work tonight everything worked fine as it did on the way home. After I got home I decided to run to the store and when I turned the key over and everything (lights, radio ect) went dead. It acted just like a bad/corroded battery terminal does but I removed the battery cables and they were clean and I brushed an reinstalled with no results. I did jiggle and follow the battery cables the best I could this time of night but found nothing. It seems it must be a bad connection or possibly a relay/fuse but I couldn't see it tonight. I will do a full check tomorrow but hope maybe someone might have some inside info on where to start.
Thanks for any help!
jeff

1981 300TDt

Just curious...was the positive wires hot ot the touch?

I had this happen, and after about 4 months and 7 jumpstarts, I finally narrowed it down to a really bad lead connector. I replaced that (.89cents) and all is well!

It is a long shot, but sometimes I overlook the simplest things...

__________________
Current: '91 300TE 4MATIC 317k and climbing...
Former:
'81 300TD Wagon 168K "Tank"
'83 240D 216K 4spd manual "Da Bear" (aka best car ever)

"Never sweat the petty things...
and never pet the sweaty things."

Is the battery dead? I once had a cell in my battery go bad and it acted like a bad connection somewhere. The way I figured it out was to charge the battery and test the voltage with no load. If it you have a bad cell in the battery the voltage will wander in the range of +/- 8-12 volts. Before you drive yourself nuts looking for a bad connection check the battery.

__________________
LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold

I agree with IRG. Check your battery before you tear anything else apart. Put a volt meter directly across the battery terminals to see if it has the ~12.7 it should have. If it doesn't, try recharging the battery. If the voltage won't increase to about 12.7 volts you probably have a bad battery.

P E H

Another easy do it yourself batter test is a load test; that's what a shop will do to determine your battery's condition. But you need a good multimeter, and a DC clamp-on is even better.

You charge the battery (if it's under 12V), wait 30 min, note the voltage, and then turn the headlights on only (have someone pull back on turnsignal lever). Use the multimeter to meter the voltage drop with the lights on. Then measure the amperage with the clamp on meter, or if you don't have one, the amperage will be I=120/lowest voltage. You may need to run the lights for 5min or so to get an accurate reading.

First of all, the voltage should not drop significantly, if it does then you obviously need a new battery. Now if you want to calculate the battery's internal resistance, use "ldelta Vl/I =R" where delta V is the absolute value for the change in the voltage (voltage drop) before you turned the lights on, vs. after you had them on for 5min or so. Solve for R, internal resistance.

Remember, if you don't have a clamp on multimeter, use only the turn signal highbeam switch for the lights, not the regular headlight switch, as that will use the running lights too. I considered 120 watts for both highbeams only, as that is a known value; unless you have cheater bulbs.

Any number I believe less than 1/10 ohm is considered acceptable for a battery in excellent condition. Anything more is indicative of problems with your battery's internal plates that cause the chemical reactions not to be up to snuff.

ATLD

Any questions; I know this seems compplicated