A bad ECU is an angle that has not been mentioned regarding my problem of 3 different new alternators not charging my new battery. I don't see ECU codes mentioned in my repair manual for this year car. Are there any for an '86?

Separate but connected question - testing my fuses, I find a live circuit for the main fuel pump - but no juice on the in-tank-pump. Does the fuel-pump-relay gizmo activate the in-tank pump ONLY when, for instance, going up hill? When does that pump get activated?

 

there's no diagnostics in LH 2.2, only in LH 2.4

the alternator to battery charging is completely indepedenent of the ECU

if your battery isn't charging, concentrate on the alternator circuites. verify the batt/alt light in the dashboard lights when you turn th ekey on, then goes out when the engine is started (possibly after blipping the throttle). if no ALT light at all, then you need to determine why (is it wiring? is it the bulb itself?). that bulb and wiring is part of the alternator charging circuit, and the alternator won't bootstrap itself without said D+ current from that circuit.

 

the in tank pump is powered when the fuel pumps are on, they go on together when the engine is running, they go off together when the engine stops running.

 

When my son and I first got his 1993 Volvo 240 the Alternator would not charge. I put a new voltage regulator in it and still it would not charge. I then went to the junk yard and got one off of a junked Volvo 240, I used the new voltage regulator and it started charging. So, I can only assume there was an issue with the diodes within the alternator. Side note: With a previous 1991 Volvo 240, I tried using Autozone Alternators and none of them would work at all.

 

Ha - thank you Pierce - as usual you cut to the chase. Yes, I thought my '86 cpu was not connected to the charging circuit so thanks for verifying that. But here's the puzzling thing, I ran 12 V's thru the circuit from D+ post on alt to charge light, to fuse and it's all fine. Where it goes from the other end of the fuse is still not clear . . . the charge light DOES go on at key postition 2 and goes OFF when engine starts running - even when the alt is not charging!
The fuse-circuit to the in tank fuel pump was dead while the rest of the fuses were powered - including the main fuel pump - AND, that fuse - to the in-tank, was not blown . . . This seems suspicious, so that I wonder IF there's a short in the in tank pump that is preventing the alternator(s) from charging? Gonna test the resistance of the in tank pump today. The second rebuilt alt DID charge up to 14.3 but then quit. When I AGAIN did the diode test on that alt, it failed the test - even tho the Auto Zone computer said that alt was ok.
The CPU in my 86 says made in the USA and has '85 magic marked on to it - so maybe it was replaced at some point - as the car was made in Sweden. How would I find the correct serial or part number-range for the correct CPU for this model car?

 

table of ECUs, not 100% complete, but reasonable enough.

basically, any LH 2.2 ECU should be interchangable. newer ones are probably better.
https://www.volvoclub.org.uk/faq/Eng...ReferenceChart

 

ericjs61 Ha! Some verification. How weird that Auto Zone alts DON"t work on Volvos. It's just a circuit - even the ECU isn't involved for my year. I have a friend with a Ford who went thru two remanufactured AZ alts and they didn't work - then a guy at AZ told him the remanufactured ones are constantly being returned - so he got a NEW alt and it worked - but not for me.

 

Rule n1. double check all electrics circuits on a old lady
rule n2 never buy from autozone lol (a JK part will suffice)

 

the other thing to check on alternators is that the ground is good. I use a volt meter, connect one probe to the ground terminal on the alternator, and the other probe to the battery - terminal, if you see any voltage there when the engine is running, you've got a bad ground. you can do the same with the B+, measure from the B+ stud on the alternator to the battery + terminal, you should see 0V... any voltage suggests a flakey B+ wire.

 

I'm with you on not buying Auto Zone stuff at this point. My friend went thru two remanufactured ones and was told secretly by an employee that those came back all the time. So he got a new one and it worked fine. A guy at this AZs said out loud in front of the rest of the employees 'about %80 of these come back' referring to the remanufactured alt. It crossed my mind that, as AZ's alts are remanufactured in Mexico, this could be sabotage on the part of Mexican workers pissed at the US. Maybe it's not AutoZone but Mexico! Anyway, done with AZ!

 

I put two extra grounds on the alternator casing to make sure it was grounded and rerouted the D+ wire to the junction box on the firewall 240's) (a suggestion from you on something you did to a 240 of yours) . l took off and cleaned all three ground connections; battery to engine block, engine block to firewall and alt casing to block. The only thing I can imagine at this point that prevented 3 alts from working is that the in tank fuel pump is shorted but only acts up when the alt is charging and this neutralizes the regulator to tell it to NOT produce 14 volts. Something is informing the regulator to not produce juice!

 

a shorted in-tank pump would blow the in-tank pump fuse nearly instantly.

a short in an unfused circuit would cause insulation meltdown and smoke, until the wiring itself failed.

I keep asking you to do some basic tests, you keep telling me about all the parts you've replaced. I don't think we're communicating here.

 

Basic tests; ground wires all cleaned and reattached; tested alt casing against ground post on battery; tested the D+ wire - grounded it to make dash charge light go on; tested all fuses for parasitic draw; with engine running, tested voltage on D+ ( which has always MATCHED the voltage on the B+ post of alt. (You say this should be 7-9 volts but not in my case)
The reason I brought up fuse 13 for the in tank fuel pump is NOT that it's blown but that it's NOT blown, YET there is no voltage at all at fuse 13 on either side. This has to be significant.
Is this what you mean by basic tests?

{{{{{{{{{{{{ CORRECTION; I was wrong about no juice to fuse 13 for the in tank fuel pump - the test I did that showed no juice was from touching both ends of the fuse and not from ground to one end of the fuse at a time.}}}}}}}}}}}}

 

By the way what is the voltage at the battery when the engine is running at say 1000 rpm

 

D+ voltage should be something like 5-9V when the ignition is on but teh engine is not running. when the engine is running, it should be same as B+, about 13.8-14.4V

 

With each of the 3 new alternators hooked up the charge was exactly the same at the battery at 1000 rpm, idle, 3000 rpms as it was before I started the car. Once a charge began with the 2nd alt and got up to 14+ volts and I thought I'd fixed the problem. But that alt stopped charging and when I did a diode test on that alt it showed bad diodes that acted up only when the alt was hot from spinning.
One clue maybe is that the alt charge light goes ON at key position 2 and OFF when the engine is on, with alternator spinning and NOT charging. Since the purpose of the dash warning light is supposed to inform you when the alt is not charging, that light should go on if alt not charging. What would inform the regulator in the alt to NOT charge?

 

Yes, I've read that info from you about 7 to 9 volts with ignition on but engine not running. This has NOT been the case for me. The D+post has exactly the same charge as the B+ post and battery + post - key position 2 and while running. Is this a clue?

 

yet the alt light is lighting up, then going out when you start? thats odd.

 

YES! It is odd. (I misdiagnosed the fuse to the in tank fuel pump - that circuit is fine.) But does the light NOT going on when the Alt is NOT charging, mean misinformation somehow going to the regulator? ( I did the test you suggested - grounding the D+ wire to make the light go on as a test that it's working properly and the light did go on). Conversely, if I link the D+ wire to the + post of the battery, the light goes on - does this make good sense?) Is something telling the alt to not charge because the battery doesn't need a charge according to the regulator?

(I took apart and cleaned the throttle position sensor in case THAT was telling the regulator the car was in idle or something)

Getting a 4th (!) new alternator on Thurs - this one not from AutoZone and made of Bosch components - so - hopes high.

 

This may be pure paranoia but as the alt problem seems to have begun when getting the car back from a garage to put a starter in - (I didn't know about the little port under the accelerator pedal to get at the difficult bolt on the starter) I can't help but wonder if a mechanic sabotaged my electrical system . . . ie; alt warning light NOT going on when alt NOT charging . . . or somehow doing something to prevent D+ tickler function working? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?