|
|
|
Hello All
I'm having a problem with my 1991 945T charging system. My alternator is not charging the battery. When I take a reading with a digital voltmeter, I get whatever the battery reads(this is while taking a reading at the alternator, both at the big red wire and the thin wire). The thin wire gets no reading if the ignition is off, 2.4v ignition on(engine off), and whatever the battery has with the engine running. The big alternator's wire gives a reading of whatever the battery has. I took the alternator to the the place I bought it(about a year ago, they rebuild them themselves), the alternator is good and they went ahead and replaced the regulator anyhow. I have bought from them and think they do a good job. I have done the following: replaced the battery, voltage regulator, both cables, the short ground wire to the alternator is in good shape, checked all the fuses. One thing to mention is that about 3 weeks ago, the idiot lights would glow for a few seconds while driving. Lately, on occation, the car seemed like it wanted to stall when making slow turns. It also has been running a bit rough. Any ideas? The car has 230K miles.
|
|
-
|
|
|
Thanks for the help. The car has been fixed! I had to put it in the back burner for a few days, I just didn't have time/patience. Well, a couple of weeks after it started acting up with the alternator, the car started making a funny noise(as if it was very low on oil). I looked at the engine and the crankshaft pulley was wobbling. I took it to the mechanic, and he said I should not drive it any more until it was fixed. The pulley was broken, I have no idea how. I asked him to fix the pulley and also look at the alternator. He replaced the pulley, and he realized the alternator belt had been slipping on the pulley. Killed two birds with one stone!!
I trully thank you for helping!
|
|
-
|
|
|
Does the alternator lamp light with the engine off and the ignition in the II position? The alternator will not charge with a burned out bulb. I just checked the small red wire on my '94 940 and got 10.8 volts with the key on position II and the engine not running. Remove the small wire and ground it and the alt. lamp should light(key position II). Let us know what you find out. John
--
"It's hell to get old!"
|
|
-
|
|
|
By the alternator light, do you mean the battery idiot light? If so, yes the battery light is comes on in the dashboard. I removed the small wire from the alt, grounded it, the voltage at that post is 1.5v, and 2.7 with the wire back on. The battery light comes on with the small wire grounded. Almost all the lights are off with that wire up in the air. I'm still getting whatever the battery's charge is for voltage.
|
|
-
|
|
|
Yes, alternator light is the battery idiot light. Is the battery light bright when lit? How does the connection at the thin wire look? Is it possible there is a poor connection between the wire and the terminal? Could you check the voltage further back from the connector? According to a wiring diagram this red wire is attached to the instrument cluster at connector c16. You might want to check the voltage coming out of this connector and see if the voltage is closer to 11 volts like my 940 has. It appears that this wire also supplies a charging signal to the manual climate control(heat and air conditioning) and abs systems. Are you having any problems with any of these units? John
--
"It's hell to get old!"
|
|
-
|
|
|
All the idiot lights come on equally, the battery light is nice and bright. I took the thin wire off the alternator twice, it was well seated and clean. Now that you mention it, a couple of days ago, the heater did not want to come on as hot as it normally does. It works OK now. I also replaced the ground wire to the alternator. I have been looking at old posts in this forum, Turbobricks.com, and Swedishbricks.com, and have come up with nothing similar to my case. I will check the voltage on the thin wire at the dash on Thursday and see how that goes. Thansks, John I truly appreciate your help!
|
|
-
|
|
|
I checked the thin wire at the back of the dash, cut the end at the alternator side and put it straight on. I get 0.4 ohms resistance on the thin wire between between the alternator and the back of the dash. I'm still getting under 3v at the back of the dash, the same thing at the alternator. I changed the lightbulb for a different one. Could the alternator's thin wire post be bad? If so, how could I check it? I am desperate, this is my work vehicle, I have to carry two batteries, one to get me where I'm going and one to get me back. I can't drive at night(don't want to use the headlights) or when it rains(required by law to turn on headlights when it rains!)
|
|
-
|
|
|
.4 ohm is a lot of resistance in the wire between the the instrument cluster and the terminal at the alternator. 3 volts is not enough to get the alt. to charge. Check the voltage reading at terminal b10 and let me know what reading you get. For a temporary fix, you could hook a small lightbulb in series with the alt. terminal to any circuit that supplies 12 volts with the ignition on. The alternator will charge then, and give you time to fix the original circuit at your leisure. John
--
"It's hell to get old!"
|
|
-
|
|
|
I tried the lightbulb, no difference. Unless I'm doing it wrong. I bought a light socket with two leads(#1157), I connected one lead to the alt's thin wire and the other to a 12v contact(even tried the battery itself), both positive and negative posts. It made no difference to the alt's voltage whether I grounded the light socket or not.
|
|
-
|
|
...it's Saturday and I expect you want to spend time on this problem. So here's my 2¢ worth—
Chele, I think you're not wiring the bulb like John meant.
Try +12 to==> socket(bulb)socket to==> Alt D+ (thin red terminal on the alternator). That should simulate the normal Key On circuit—but maybe with more current than normal with that 1157 bulb. Try starting. If Alternator works, test light should go out.
That thin red wire to D+ does two things:
1- Makes a ground path for the Batt light (and others*, via diode connections) TO and thru the alternator to ground.
The current flowing from bulbs to alternator is what lets the Alternator produce voltage as it "spins up".
2- Carries Alternator voltage back to the bulb circuit to turn the lights OFF when the Alternator is charging. The D+ terminal (was a ground) rises to Alternator B+ level. With voltage now on both sides of those bulbs, no current flows thru them and they go out.)
I just made these tests on my '93 940 (100A Denso)...
Key OFF, D+ wire DIS-connected:
Alt D+ terminal to ground=47.5 ohms (same on alternator frame or Valve cover)
Key ON (Batt and other 4 lights off). Red wire terminal from bulbs = 11+ volts.
Connect wire to D+, warning lights come on.
>>You must see near +12v on disconnected red wire with KEY ON.<<
* The other bulbs whose current adds to that of the Batt light are:
• Parking Brake
• Brake Warning
• Bulb Failure
• Washer Fluid level
• and maybe Service indicator
--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
|
|
-
|
|
|
I thought I had already posted this, but I don't see my post. My apologies if it's a double post. The alternator had been acting up for a couple of weeks. This week, the engine started making quite a bit of noise, as if it was really low on motor oil. I checked and noticed the crankshaft pulley was wobbling. I took it to the mechanic and he sugested I not drive it until it was fixed. I asked him to also look at the alternator problem. After replacing the crankshaft pulley, he realized the alternator belt had been slipping on the pulley. The problem went away after replacing the damaged pulley.
I truly appreciate the help.
Chele
|
|
|
|
|
