Problem with Delco 50DN and/or Delco Remy Voltage Regulator

wagwar · June 30, 2014, 01:36:34 PM

Ok, I may have broken something. I was trying to install a Sterling Advance Regulator in my bus. I had it wired and configured properly according to the mfg. but it was not working. When it would kick in, the voltage out of the alternator would go up to 35 and then the adv. regulator would kick out. The original regulator was still in line, so it would take over and bring the voltage down to 27 or so. So, no harm done I thought.

So I disconnected the adv. regulator and started the engine to be sure everything was OK, but it is not. Now the alternator immediately goes to 35 volts and will not come back down. Either the old VR is stuck or the alternator is stuck or both?

I've tried disconnecting the batts and the field to the regulator and then reconnecting - no change. I could really use some help.

Thanks!

gus · June 30, 2014, 02:42:59 PM

If I understand correctly you had both VRs connected is series.

Why did you do this? It makes no sense?? Did the inst say to do this?

I also assume the Advance Regulator is solid state. If so you may have destroyed it but it appears there is more of a chance the old one was destroyed than the new one.

Anyway, having two VR is series would seem to completely confuse the alt.

If the alt is going to 35 volts the field is getting the full 24 volts somehow, don't run it long at this voltage. (Needless to say)

I don't see how the alt could be stuck, it completely depends on field voltage, but stranger things happen?

luvrbus · June 30, 2014, 03:29:55 PM

It's a ground problem

wagwar · June 30, 2014, 04:43:26 PM

Thanks!
Yes, the instructions and several conversations with the mfg. told me to leave the old VR connected and add the new adv. regulator to the Field connection on the alternator. That is why I did that. Their reasoning is that should the adv. VR fail, the old regulator will pick up where the adv. left off. Now however, as I said, with the new adv VR disconnected entirely, when I start the engine the alternator immediately goes to 35 vdc and stays there. Needless to say, I shut it down immediately.

LUVRBUS: You said is was a ground. Could you be more specific?

wagwar · June 30, 2014, 04:47:43 PM

addendum to previous post:
Is the Delco 50DN a Positive Field control alternator OR is it a Negative Field control alternator?
The mfg. TS rep did not know which it was (Delco 50DN gear driven, oil cooled, etc.). He said most likely it was a Positive and that is how I configured the adv. regulator. Apparently, some alternators(European) are Negative Field control.

gumpy · June 30, 2014, 06:58:23 PM

when I put a solid state regulator in my bus, I had to run a wire directly from the battery to the regulator. Connecting the normal voltage sense wire from the old
regulator didn't work. I think it was too corroded somewhere for it to sense proper voltage. Adding the wire directly to the battery worked perfectly.

My guess is you either are not getting voltage sense to the regulator, or the regulator is not grounded properly.

Is there a cut in relay in the system?

wagwar · June 30, 2014, 07:29:18 PM

there is a cut-in relay. The alternator must be producing voltage before the Not Gen TT light goes out.

Which regulator are you referring to? the OEM or the adv VR?

The OEM VR and alternator were working OK before I installed the adv. VR.

Thanks.

Jon · July 01, 2014, 03:28:13 AM

Jim,

Maybe you might want to do a little basic isolation of the problem. Start by restoring the bus to original and see if the 50DN and the original VR work as intended.

Then take the original VR out of the system and see if the new one works without the original. My real concern is if the new VR said to leave the original VR in the system in case the new one fails then what confidence does the manufacturer really have in their product. If you are getting 35V output on the 50DN that tells me something is maintaining power to the field when it should be regulated so one of the two (or maybe both VRs now) are messed up.

gumpy · July 01, 2014, 05:30:11 AM

Quote from: wagwar on June 30, 2014, 07:29:18 PM
there is a cut-in relay. The alternator must be producing voltage before the Not Gen TT light goes out.

Which regulator are you referring to? the OEM or the adv VR?

The OEM VR and alternator were working OK before I installed the adv. VR.

Thanks.

Either regulator. They're connected the same way.

Is your air pressure built up? The cut in relay doesn't engage until air pressure is at a certain level.

Wat is you bus and engine/alternator configuration. I looked at your profile but that information is not there. I looked at your blog briefly, but didn't want to wade
through it trying to find the info.

wagwar · July 01, 2014, 09:09:32 AM

1981 MCI MC9, 6v92t, Delco 50DN.
Update: I took the old VR in to be tested. It was cooked. I have purchased a new VR to replace the old one. I have disconnected the new adv. VR and am going to test to see if the alternator has been damaged.

wagwar · July 01, 2014, 09:26:00 AM

I installed the new old VR. Aired up the bus and fired up the engine: no charging from the alternator. I can only conclude that the adv VR cooked my old VR and the alternator itself.
Any other possibility?

Jon · July 01, 2014, 09:45:34 AM

Start with a basic check. Apply voltage from the battery to the field post on the alternator and watch the voltage on the alternator output. Be prepared to pull the jumper from the field post so as to not end up with unregulated run-away voltage. If the alternator is working which will be seen by voltage readings in excess of the initial voltage reading you at least know the alternator is functioning.

The next step is to verify one or both of the VRs are not working. When hooked up and the engine running at high idle you should be seeing 27.7 to around 28.0 volts.

gumpy · July 01, 2014, 09:47:43 AM

Direct drive alternator or belt drive?

So you hooked the regulator up to the original wires?

What voltage do you have at the positive terminal of the regulator?
There's a relay and fuse in the circuit. Could be one of those.

There's a section in the maintenance manual on testing the alternator diodes.

bevans6 · July 01, 2014, 10:02:06 AM

my feeling is that the alternator is OK since it was producing 36 odd volts when it had voltage at the field terminal. If the new regulator doesn't have a good solid ground it won't output a field voltage and the alternator won't produce power. If the regulator doesn't have a solid connection to sense the battery voltage it will put out a constant field voltage and the alternator will produce too much voltage. You can't really measure field voltage with a meter properly, it turns on and off at a high frequency when all is working properly. Different regulators have a different frequency, it can be up to 20 khz from what I have read.

Brian

wagwar · July 01, 2014, 10:14:30 AM

Thanks for all of your help!
Update: The shop that sold me the new old VR gave me erroneous instructions for installation. The new old VR has an IGN terminal which the old VR did not. The shop said I did not need that connection. I came to the same conclusion as Brian, that if the alt. was producing 35 volts it must be OK. So I called the shop and spoke to a technician - IGN does need a connection. So I jumpered between the Batt post and the IGN post and all is working again! I also tested to be sure the Batt post is only hot when the key is on so that I don't slowly drain the start batteries.
I am back to a functioning system.