Intermittent Charging 92 volvo 740

briguy1960 · Post by **briguy1960** » 30 Jan 2012, 17:08

Hello all,

I am having some very weird electrical issues with my 740. Sometimes It starts and drives fine. Other times it starts but it is obvious that the (brand new) alternator is not charging. Dim lights, slow blower fan /wiper. and a sub 12 volt reading out of the cigarette lighter. Usually flicking the lights on or off or turning on the fan will cause the charging system to "wake up " and then it works properly. I have taken apart all the high amperage connections and engine chassis grounds and done voltage drop tests but there are no issues there. The alternator in a nippon densi and I replaced the old one but the symptoms did not go away

There are just two wires exiting the alternator one fat one skinny and I am assuming the regulator is internal. I suspect maybe something is not allowing an exciter voltage to get to the alternator to make it charge. I've tried juggling the key switch. Does anyone know if the control (exciter) voltage to the alternator is controlled from the ECU or is it from the key switch?

BTW this Volvo has the Rex Regina system

Any other ideas or questions?

Thanks

B

briguy1960 · Post by **briguy1960** » 30 Jan 2012, 18:46

OK , so to answer my own post, indeed its seems like no voltage is getting down the skinny wire to the alternator.I piggybacked a wire onto that terminal and touching it to the + terminal gets me charging again. So back to my last quesion, does anyone off hand know the current path from the battery to get 12v + to the alternator. Alternately cannot I just find a part of the fuse block that is key switched and hook in there. I do not have a manual anymore for this car. Loaned it to a "friend" who left town. My Stupid I know.

briguy1960 · Post by **briguy1960** » 30 Jan 2012, 21:58

Well, I'm back up and running---after a fashion. Ran a wire from the alternator through the firewall. Easy to do as there is a unused rubber bung just below where the main wiring loom runs in. A quick poke with a 1/8 drill and we are through. Up and across and into the fuse block on fuse 14 (radio) and good to go . It then that I realize that none of the idiot lights (that's what we call them here in Canada ) light up when the key is in the run position with the engine not running. Funny how you miss stuff like that. So I am thinking the ignition switch is probably getting a bit dodgy. Sad to say even though this has bee a decent car the litany of little things, mostly electrical, is causing me to start looking for a replacement. Needs a head gasket (seeping oil and coolant out between number 1 and 2 cylinder). Needs an exhaust system, and an alignment, brakes have not been touched in four years----hmmm . Gotta get through emissions testing in a couple of months, that could be the tipping point. Anyways, hope someone gets something out of this little missive

Post by **billofdurham** » 31 Jan 2012, 12:26

The exciter voltage is through the ignition key BUT it relies on the battery idiot light being on. If that bulb is blown or not working for whatever reason there is no reaction from the alternator.

BTW we call them idiot lights over here as well.

Bill.

briguy1960 · Post by **briguy1960** » 31 Jan 2012, 23:29

Wow that is a very interesting. Hopefully the bulb is super reliable. The only lights on the dash cluster which light anymore are the seat belt reminder light, the service light, which goes out after 30 seconds and the high beams indicator. Wonder if some big connector has fallen off the back?