1978 Volvo 245

[gtomblingson]

Hi all, I recently became a old volvo fanatic and decided to initiate myself by purchasing a 1978 245 DL. Long story short, it came with a bad alternator so I'm trying to replace it myself and I've hit a road block. Perhaps someone could pass on some advice.

The old alternator was an actual volvo alternator that utilized an external voltage regulator. I've replaced the old regulator with a new external regulator and rebuilt the wiring harness with 14ga wire and insulated spade clips. The new alternator has the outlet to the external voltage regulator just as expected so there's no problem there. Additionally, the new alternator has the typical bolt for the big red wire.

Here's my problem. If I simply attach the big red wire and the harness for the external regulator, I'm lacking a complete circuit, right? There has to be something missing. Could anyone explain to me how the circuit is typically completed on an alternator. It's just a one way street:

Red wire ---> alternator ----> red/green/brown wire to voltage regulator

if this isn't clear feel free to ask for additional info. I thought I had it all figured out when I took off the old alternator but now I fear that I've missed something. I'll be checking up with the post regularly.

Thanks all and happy motoring.

[Three Fat Tigers]

Besides the three wires to the regulator and the heavy red wire to the battery, there should be a ground wire connecting the body of the alternator to the engine block, usually at one of the bolts for the lower alternator bracket. And there should also be a small red wire that connects the battery/charge failure idiot light to the alternator.

Make sure you see the charge idiot light when you turn on the ignition as power passing through that lamp to the alternator is what creates the initial magnetic field inside the alternator before it starts rotating. Without that it might not charge at all or until the alternator reaches something like 4k rpm.

Also if I'm not mistaken, the external regulator also has a separate ground wire or is otherwise grounded by the mounting point.

[gtomblingson]

Thanks for the response. After some hunting I found the smaller red wire. It was a little too short for the alternator and had the wrong attachment on it so I trimmed it, spliced it to some new wire, added a female spade clip and hooked it all up. There's no ground output on the new alternator so I'm assuming it's grounded internally. Additionally, the external voltage regulator is likely grounded to the car's body.

I managed to get it all together last night and the car started up just fine and all the dash lights came on including the "AMP" idiot light i believe. This morning, I checked voltage across the battery and it read 12.7. After firing up the engine however, it dropped to 12.16. I had my friend rev the engine a bit and it never went up so I'm still concerned. There's no tach so I can't be positive about the rpm we were at. I should try again and rev it higher I suppose.

Any further advice on how I should test it? Or what else could be the problem? I am still concerned about belt tension as I simply fudge it. It's spinning fine with no noises and there's no way I could over-tighten it (I'm a pretty small dude).

By the way, your response was very helpful and I thank you very much for helping me out. I'm in love with this car and would really like to see it on the road again. Unfortunately, I'm a little too freaked out to drive it yet.

[MrBill]

Thanks for the response. After some hunting I found the smaller red wire. It was a little too short for the alternator and had the wrong attachment on it so I trimmed it, spliced it to some new wire, added a female spade clip and hooked it all up. There's no ground output on the new alternator so I'm assuming it's grounded internally. Additionally, the external voltage regulator is likely grounded to the car's body.

No the alternator must be grounded. I haven't owned a 240 that old, but I'm pretty sure all the alternators (2/7/9 series) mount on bushings, preventing a ground from occuring.

On the perimeter of the alternator (back side) there should be some studs to attach a ground wire.

Maybe look into an internally regulated alternator.

On my 82 242, I replaced a failed system (utilizing a ford regulator and a 60amp bosch unit) with an internally regulated alternator.

I now have an 80 amp nippon-denso alternator from newer 700/900 cars. Much smaller and more accessable. You need the tensioner from the newer car also (i got the whole thing at a junkyard for $15)

Hopefully it works out.