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big ham · 05-23-2020, 12:39 PM

My 2000 Diplomat dash volt gauge,under load and/or sitting idle, will read 13+ until I turn on the lights. It then will show 12.5 and drop below 12 with constant light usage. This makes it impossible to drive at night or in the rain. No alternator light blinks or shows. Wiper usage has the same effect.
Would this be a definate weak or failing alternator? I have changed the house and chassie batteries without any change to the issue.

mackpeteno · 05-23-2020, 12:44 PM

Quote:

Originally Posted by big ham

My 2000 Diplomat dash volt gauge,under load and/or sitting idle, will read 13+ until I turn on the lights. It then will show 12.5 and drop below 12 with constant light usage. This makes it impossible to drive at night or in the rain. No alternator light blinks or shows. Wiper usage has the same effect.
Would this be a definate weak or failing alternator? I have changed the house and chassie batteries without any change to the issue.

My 99 Country Coach is doing the same thing.Have not been able to solve it yet.

twinboat · 05-23-2020, 12:53 PM

Failing alternator or loose drive belt.

Run it for 15 minutes with the lights and wipers on. Then shut down and feel the alternator pully. Caution it may be hot from slipping belt.

36PFT · 05-23-2020, 01:04 PM

Check the voltage at the chassis batteries. Make sure the batteries are full and terminals are tight. If you get the same reading, then it is probably the alternator.

8.3Oilbuner · 05-23-2020, 03:12 PM

Hi Big Ham; Agree with 36PFT. Monaco used very poor wiring and grounding on the dash gauges. I have a Silver Leaf monitor and it gives more accurate info from the engine ECM. Check the voltage at the battery terminals with the engine idling at least around 800 RPM. Add loads after you get a reading and see if the voltage continues to drop. If so, your alternator could be headed south. On my 01 Windsor I get 14.0 to 14.3V at the battery terminals when idling. I can load up the chassis electrical system, headlights, dash blower speed, wipers and etc. and still get a reading of 14.0V on my Silver Leaf and the battery terminals while the dash voltage gauge continues to drop.

veraken · 05-24-2020, 05:16 AM

I had the same problem, turned out to be a bad alternator. I found the best price at Quality Power. I decided to replace my 160 amp Leece Neville with a 200 amp Delco Remy 28SI. The install was fairly simple except on the DR you don't connect the excite wire since it is self exciting. I had my old LN rebuilt and carry it as a spare.

https://www.qualitypowerauto.com/cat...lternators.htm

In the interim, you can run your generator to keep your battery charged.

Cj D · 05-24-2020, 06:59 AM

Like everyone has said, check the voltage with the lights and wipers on at the batteries. If it is above 12.7v there, then you likely have a ground to the gage set that needs cleaning. If the voltage is below 12.6 at the batteries, you definitely have a bad alt or alt connection.