AC from Onan

[loren \(skip\) newhouse]

I can use some advise and/or direction. Yesterday, I started the Onan in
mY '75 Avion GMC so I could have some air-conditioning while I worked in
some upgrades in the coach. The outside temperature was in the nineties.
The Onan and the AC worked fine for a while. Then the AC shut off. I
checked other 120vac circuits and found them to be dead. However, the
Onan kept running. I checked breakers in the Panel and found them to be
okay. I shut off the Onan and pulled the drawer to see if the breaker on
the generator had tripped. It was okay. Checked today to see if the heat
might have been the culprit. Alas I still have no current from the
Onan. Any advice will be appreciated.
Skip Newhouse

 

[john wright]

It appears that your bridge rectifier may have failed. Do you have a
service manual for your coach? Not an expensive item just difficult to
get at correctly.
There have been recent posting on this problem and anyone else who has
the number handy please post.

J.R. Wright

>
> I can use some advise and/or direction. Yesterday, I started the Onan in
> mY '75 Avion GMC so I could have some air-conditioning while I worked in
> some upgrades in the coach. The outside temperature was in the nineties.
> The Onan and the AC worked fine for a while. Then the AC shut off. I
> checked other 120vac circuits and found them to be dead. However, the
> Onan kept running. I checked breakers in the Panel and found them to be
> okay. I shut off the Onan and pulled the drawer to see if the breaker on
> the generator had tripped. It was okay. Checked today to see if the heat
> might have been the culprit. Alas I still have no current from the
> Onan. Any advice will be appreciated.
> Skip Newhouse

 

[richard guthart]

Skip,

My Onan quit suddenly a couple of weeks ago. Turned out to be the bridge
rectifier. Here's a repost of Duane Simmons' response to my question, which
enabled me to fix it:

Richard Guthart
The Onan failure that you have describe is a classic "Bridge Rectifier"
(BR) failure. However, they typically fail while turning off the Onan
while the AC is running. A voltage transit is generally the cause of
failure due to the fact that the OEM Bridge rectifiers are operating very
near to the Peak Inverse Voltage (PIV) rating of the OEM Bridge
rectifier. A simple solution is to replace the OEM BR with one of much
higher rating. However, I have not been able to find any aftermarket
BR w/the same pin-outs. A simple modification to the base (holding
device) is capable to accept the four wires as feed thru(directly
attached to the terminals of the BR). A 1/4" hole in the base for each
wire is all that is required.
To remove the BR, side out the Onan as far as you can & remove the BR
mounting screw which is located aft of the Control Board on the rear
Generator Housing (1/4" screw head). Remove the plastic cover on the
side of the generator housing & the BR can be moved to where you can ID
the terminal from the side of the BR. Carefully...Carefully....Carefully
transfer the terminal ID to each wire (ie. + , - , AC , AC).
Transferring the proper ID is very important since the Onan will not
operate with crossed wires & the wires are very hard to trace for ID. Now
individually remove the wires from the base (relive tab on each wire
terminal from the front/BR engagement side & push terminals out the
rear). Now drill 1/4" holes for each wire. Slide the wires thru the
proper hold & attach/slide on the 4 wires to the BR. Slide the BR & wire
terminals back down thru the base to where the Original mounting screw
will secure the BR to it's original position on the housing.
An after market BR w/1,000 volt (PIV) rating is available from many
Electronics stores at less than $10. The PIV is greater than 3 times the
OEM BR & should never fail (well almost never). NTE # 5328 is the after
market BR that I use.

Good Luck
Duane Simmons

> > I can use some advise and/or direction. Yesterday, I started the Onan in
> > mY '75 Avion GMC so I could have some air-conditioning while I worked in
> > some upgrades in the coach. The outside temperature was in the nineties.
> > The Onan and the AC worked fine for a while. Then the AC shut off. I
> > checked other 120vac circuits and found them to be dead. However, the
> > Onan kept running. I checked breakers in the Panel and found them to be
> > okay. I shut off the Onan and pulled the drawer to see if the breaker on
> > the generator had tripped. It was okay. Checked today to see if the heat
> > might have been the culprit. Alas I still have no current from the
> > Onan. Any advice will be appreciated.
> > Skip Newhouse
>

 

[jim green]

I spent $11 on a rectifier from a local electronics shop to cure mine after
hosing it down last year. You have to modify the connection slightly. Not a
problem.
- ----- Original Message -----
From: John Wright
To:
Sent: Saturday, July 17, 1999 7:39 PM
Subject: Re: GMC: AC from Onan

> It appears that your bridge rectifier may have failed. Do you have a
> service manual for your coach? Not an expensive item just difficult to
> get at correctly.
> There have been recent posting on this problem and anyone else who has
> the number handy please post.
>
> J.R. Wright
>

> >
> > I can use some advise and/or direction. Yesterday, I started the Onan in
> > mY '75 Avion GMC so I could have some air-conditioning while I worked in
> > some upgrades in the coach. The outside temperature was in the nineties.
> > The Onan and the AC worked fine for a while. Then the AC shut off. I
> > checked other 120vac circuits and found them to be dead. However, the
> > Onan kept running. I checked breakers in the Panel and found them to be
> > okay. I shut off the Onan and pulled the drawer to see if the breaker on
> > the generator had tripped. It was okay. Checked today to see if the heat
> > might have been the culprit. Alas I still have no current from the
> > Onan. Any advice will be appreciated.
> > Skip Newhouse

 

[loren \(skip\) newhouse]

> It appears that your bridge rectifier may have failed. Do you have a
> service manual for your coach?

Hi John,I do have a service manual. as a matter of fact, I have two. One is
from Onan. The other is from GMC Motorhomes International. It is similar to
the original, but has more info. Not too much about Bridge Rectifiers.

Hi Richard and Gene,

Thanks for the info on how to replace the Bridge Rectifier. The GMCMI manual I
mentioned above tells how to test the rectifier with an Ohmmeter. I suppose I
should do that before I remove and replace the existing rectifier, right?

All help continues to be appreciated. This net is just great.
Skip

>

 

[rob teed]

You need to replace the BRIDGE RECTIFER I bet.
Someone will give you the part number.
Rob Teed 74 Painted Desert

> -----Original Message-----
> From: owner-gmcmotorhome
> [mailtowner-gmcmotorhome]On Behalf Of Loren (Skip)
> Newhouse
> Sent: Saturday, July 17, 1999 5:58 PM
> To: gmcmotorhome
> Subject: GMC: AC from Onan
>
>
> I can use some advise and/or direction. Yesterday, I started the Onan in
> mY '75 Avion GMC so I could have some air-conditioning while I worked in
> some upgrades in the coach. The outside temperature was in the nineties.
> The Onan and the AC worked fine for a while. Then the AC shut off. I
> checked other 120vac circuits and found them to be dead. However, the
> Onan kept running. I checked breakers in the Panel and found them to be
> okay. I shut off the Onan and pulled the drawer to see if the breaker on
> the generator had tripped. It was okay. Checked today to see if the heat
> might have been the culprit. Alas I still have no current from the
> Onan. Any advice will be appreciated.
> Skip Newhouse
>
>
>
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