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Thanks to you all for your advice however, the charging mystery on my 1993 Volvo 940 continues. I have replaced the battery with a new Interstate battery, had the alternator rebuilt (Denso 14v 100A), checked and cleaned all wiring terminals including the ground connect and noted the following:
(1) With the engine off, the voltage across the battery terminals is ~12.7v which is normal.
(2) The car starts easily and, with the engine running, the voltage across the battery terminals reads ~14.4v which indicates that the alternator is charging properly.
(3) After driving the car for about 20-25 minutes, while leaving the engine running, the voltage across the battery terminals reads about 12.3v. This indicates that it is not charging.(No lights or fan were on during the measurement.) Charging appears to be intermittent. The belt from the crankshaft pulley to the alternator is properly tensioned. So, I am baffled???
The only thing that I have observed is that when I start the car, sometimes all the dashboard lights come on(which is normal when the key is switched to the ignition on) and sometimes only two lights come on. In either case, the car easily starts.
Any insight will be appreciated.
Many thanks,
OnlyVolvo
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I think the key here is the intermittent lights before starting the engine.
The alternator circuit is laid out such that there is a wire that goes from the alternator to the instrument cluster, and then either to ground or back to the alt. This is the "excited wire". Often, people have a burned out bulb in the cluster for the battery light, leading to an intermittent or constant no-charging situation.
Since your dash lights come on differently some times than others, I would figure that out. I think it will lead you to the issue.
I can think of two ways to do this:
1) Put the key in the ignition, and see if the lights come on. Hook up a meter to the alternator b+ and ground when the battery light does not illuminate. Start the car and watch the voltage. Do not rev the engine at this time.
2) Get the car into a situation where it is not charging, then turn it off, turn the key back to run (engine off) and see if the battery light is on.
I think that you have an intermittent connection to your cluster. Maybe a bundle of wires gets yanked on or moves while driving. I think that if you pull your cluster, the problem may be pretty obvious - somewhere between a burned trace and corrosion on a connection. You want to be very gentle with the plastic film circuit board connections.
The other thing I've seen baffle someone is that their alternator was missing its ground strap. This matters because on RWD Volvos, the rubber bushings actually can isolate the alternator body from the bracket.
Have you checked for voltage between the ends of your battery cables? This would be from the battery post to the alternator b+ terminal, not on the actual cable ends. I've had corrosion accumulate *inside* of a terminal lug, and cause issues. You should see around 0.1-0.2V end to end on the cables. Resistance should be (far) less than 1 ohm.
Good luck!
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Please see here:
https://www.brickboard.com/FAQ/700-900/ElectricalStarting.htm
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"After driving the car for about 20-25 minutes, while leaving the engine running, the voltage across the battery terminals reads about 12.3v. This indicates that it is not charging.(No lights or fan were on during the measurement.) Charging appears to be intermittent"
--> When its not charging get voltage measurement at the alt itself - between B+ post to its own body. If voltage is present then there could be conduction issue with your alt grounding wire (the blue wire from alt body to inlet manifold). The wire could still be conducting but has developed internal resistance high enough due to age thus not reaching ground (zero volt) level.
Which dashboard light lights up during ignition on? Does the one with batt icon lights up too?
Amarin.
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Since it happens when driving I bet you need new positive & negative cables.There most likely isa crack in the cable///This wouldnt happen w American cars cause they take a big crap & die at 100,000 miles!!
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The only dash lights that illuminate when the ignition is in the ON position are the seat belt and SRS warning lights.
Any comments will be appreciated.
Many thanks!
OnlyVolvo
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"The only dash lights that illuminate when the ignition is in the ON position are the seat belt and SRS warning lights."
--> The seat belt light has its own power and ground, not depending on the dashboard circuit. But the SRS light has same power supply as for other indicator lights. So there could be issues with:
1. The other bulbs - i.e. blown out/poor contact/corrosion
2. Poor gounding - check board connectors labelled B and C for corrosion. Labels B and C are printed on the flex board.
3. Reflow those solder points on the flex board - touch briefly with soldering iron not more than 1 sec otherwise flex board will melt
But to address your charging issue as first priority, check your batt bulb for any blowout. If bulb is good then check for any voltage at the bulb's contacts on the board. The wiring harness should be long enough to allow for these checks (dashboard still all connected) while you turn ignition to KPII.
Amarin.
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Thanks for your timely reply to my message...
The latest:
(1) When all the warning lights on my dashboard light up with the ignition switched to position II, the (on) position, the alternator works fine and the battery charges properly (13.5-14.4 VDC). (Battery warning bulb is fine.) However, when only the seat belt and SRS
warning lights illuminate, the alternator does not charge the battery.
(2) It is my understanding that the warning lights provide current to the alt via the alt excite wire to activate the alt stator. With only the seat belt and SRS lights, no current is flowing to the alt which is presumably why it does not charge.
(3) The dashboard warning lights all come on but this is only intermittently.
(4) I have removed the instrument cluster and checked for cold solder joints on the flex circuit board. It is not obvious that there are cold solder joints however, I have been advised to reflow all of the solder joints and then reinstall the instrument cluster. Evidently, the root cause for alt lack of charging is related to the warning lights/alt excite current...
I would welcome your comments as I have a new battery, a freshly rebuilt Denso 14v 100A alternator and all cleaned wire terminals. I am hoping that reflowing the flex circuit solder joints will solve the problem.
One mystery still remains.. When the alt is functioning properly and charging the battery, it gets very hot... measured at ~120 deg F. No one has been able to explain this. Any thoughts?
Many thanks,
OnlyVolvo
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"One mystery still remains.. When the alt is functioning properly and charging the battery, it gets very hot... measured at ~120 deg F. No one has been able to explain this. Any thoughts?"
--> How did you come to this conclusion? Unless engine was just started not fully warmed up and yet you find the alt already running hot - that would be unusual. My alt has running temp about 160F after a long drive, even more after being in traffic crawl. As the alt sits in engine bay its open to all the heat in there.
Amarin.
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Dear Amarin,
Hope you're well. After a 25-minute drive - at speeds not exceeding 90 Km/h (and that only briefly) and with an ambient temperature about 22⁰C (71⁰F), an infrared thermometer showed 71⁰C (160⁰F) at the top of the alternator's casing.
I'm quite sure this alternator is in good order.
Thus, an alternator casing temperature of 49⁰C (120⁰F) would only be concerning were it to occur after just a few minutes of operation.
The "run time" of the alternator on the car in question is as yet unknown.
Hope this helps.
Yours faithfully,
Spook
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Dear Spook,
I redo the temp readings (using handheld infrared thermometer) on mine, this time with closer monitoring. Ambient temp 31C (87F) car partially parked in sunlight at midday. Hood open at all times during test. No road drive so that our OP could do similar setup.
Engine off --> alt 35C (95F)
Engine running about 5 mins and upper radiator hose warm --> alt 40C (104F)
Engine running about 10 mins and upper radiator hose hot --> alt 45C (113F)
I didn't wait till the radiator fan runs lest my good neighbour start taking notice : - )
To the OP:
If your alt temp similar to above findings then nothing to worry about.
May these help,
Amarin.
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Dear Amarin,
Hope you're well. I presumed that the engine had just been started and that the car was stationary.
When ambient temperatures are, say, 32⁰C (90⁰F), it won't take long before the alternator casing's temperature reaches 49⁰C (120⁰F).
As an experiment, I'll see how long it takes at, say, an ambient temperature of 21⁰C (70⁰F), for the alternator on my car to reach 49⁰C. This test will be done with the car parked.
As I have to be out-and-about today, I'll take with me an infrared thermometer, and measure the alternator's temperature at various points. I'll report my findings.
Hope this helps.
Yours faithfully,
Spook
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Dear OnlyVolvo,
Hope you're well. "When the alternator is functioning properly and charging the battery, it gets very hot...".
This high temperature reading can mean: (a) the alternator, though new, is defective (internally shorted) and/or (b) a cable - that connects the alternator to the battery or to the ground - is corroded and so offering resistance that should not be present.
The thin red wire - that connects the alternator to the instrument cluster - provides the current needed to initiate charging. Thereafter, that current isn't needed.
Sometimes a re-built part is defective. That was reported recently, as to a starter.
I'd find a "known-good" used alternator, and install it. If a "known-good" alternator also over-heats, then I'd focus on the cables.
Hope this helps.
Yours faithfully,
Spook
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The fault may be in your instrument cluster?
Art Benstein and Spook and other board members are well and way better practiced at 700 and 900 series instrument cluster diagnosis and service. I've not seen a 700-900 series cluster in person for maybe four years now.
Yet what you describe here is a fault in the instrument cluster or connection to it.
The instrument cluster indicator lights should all illuminate when the ignition key is in and turned to the second position, what Art and other, and maybe the auto industry would call key position (KP) II. Maybe from the Volvo Cars AB corp coda or codex.
The instrument cluster lights, when they illuminate, specifically the battery light, allows the D+ voltage to excite the stater or rotor (armature) coils to present a magnetic field so the alternator begins charging immediately in engine start. Else, you'd have to rev the cold engine to 3000 RPM or so to start the alternator process to produce voltage and current.
The 700-900 series instrument clusters can fail sometimes in minor ways to cause larger, yet easily serviced, issues some some ways. The Volvo 700-900 FAQ entries may help you.
Electrical: Instruments
https://www.brickboard.com/FAQ/700-900/ElectricalInstruments.htm
See under subheading Gauges or Warning Lights Stop Working Intermittently, Alternator Fails: Failing Flex Circuit Connections:
[Andrew Woods] I've had an intermittent fuel gauge, warning lights, and a Alternator exciter circuit repair on flex panel.jumpy tach, as well as an alternator that would not work till I revved the engine up past 2k rpm's, all due to faulty connections on the instrument cluster. ...
At essence, the alternator is not getting a D+ VDC charge. Yet may not exclude some alternator failure. Yet you certainly have cluster failure or connection to the cluster failure. (Them little solder welds on the cluster flexi pc board.
Use proper soldering pencil or iron. Not too hot! Like so hot it is better for leading up some stained glass forms! (Or roast a pizza with extra anchovies, cause I love anchovies on pizza St. Louis style.)
Sorry not to make mention in my earlier post. I was not grasping the full causal nature of your issue with the intersecting systems that may effect it.
Volvo Electrical: Instrument Panel Repair
https://www.brickboard.com/FAQ/700-900/ElectricalInstrumentsPanelRepair.htm
Volvo Instrument Cluster Interchangeability
https://www.brickboard.com/FAQ/700-900/ElectricalInstrumentClusterInterchangeability.htm
You do not mention speedo failure, yet here ya go:
https://www.brickboard.com/FAQ/700-900/ElectricalSpeedometerRepair.htm
Some wiring diagrams for you, also, and everyone else:
http://www.v8volvo.se/mekartips/volvo/index.html
Hope that helps yooooooo.
Sure Happy it's Wednesday! (Or Happy Friday Eve?)
Earl Grey Tea MacDuff with some fresh Powdered Ginger for the Anti-Inflammatory
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"Art Benstein and Spook and other board members are well and way better practiced at 700 and 900 series instrument cluster diagnosis and service."
Spook yes, Art Benstein no. I got curious and learned something about the Yakazi speedometer capacitor leakage, but that's the extent of my expertise in this area.
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Art Benstein near Baltimore
“Never underestimate the difficulty of changing false beliefs by facts.” --- Henry Rosovsky
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