Welcome! Please use the navigational links to explore our website.
PartsASAP LogoCompany Logo Auction Link (800) 853-2651

Shop Now

   Allis Chalmers Case Farmall IH Ford 8N,9N,2N Ford
   Ferguson John Deere Massey Ferguson Minn. Moline Oliver

Crawlers, Dozers, Loaders & Backhoes Discussion Forum

CAT 955H Generator problem

Welcome Guest, Log in or Register
Author 
Norcal Dave

07-20-2007 10:47:41




Report to Moderator

I've got a CAT 955H Traxcavator #60A-7963 (mid 1960's). We are having battery issues, in that we have to jumpstart it with 2 cars each time we operate it. I believe we determined its a 24V system, and I am going to test it with a multimeter this weekend, while operating, to see what charge it has. I'll do this by placing the multimeter probes one on each terminal on one of the two batteries, while leaving the battery cables on. With a 24V system, I'm expecting to see a reading of about 25V or so, which will tell me if the generator is producing a charge.

If I don't get a reading, or get a significantly lower reading, on one or both batteries, is there a way to test the generator in place to see if its producing power, or if I have another problem?

One battery is relatively new, and the older was tested by a battery shop as good. So I can basically guess my batteries aren't the problem. I'm guessing that leaves me with one of two problems: A) the generator doesnt work or B) I have a short in the battery cables or somewhere that is sapping the battery strength.

What do you think, and how do I test a generator?

[Log in to Reply]   [No Email]
Bob Plumadore

07-20-2007 16:44:18




Report to Moderator
 Re: CAT 955H Generator problem in reply to Norcal Dave, 07-20-2007 10:47:41  
you check your voltage and charging across both batteries. the positive terminal goes to the starter selnoid, the negative goes to the key switch then to the ground terminal on the starter.
the two batteries have a crosse over cable from the negative of one to the positive of the other.
you can disconect the field wire t the requlator and ground it the generator should put ont.



[Log in to Reply]  [No Email]
AJK

07-20-2007 16:18:56




Report to Moderator
 Re: CAT 955H Generator problem in reply to Norcal Dave, 07-20-2007 10:47:41  
Your 955 is 24v but it must be wired in series, the main cable from the starter motor solenoid should go to the positive pole of one battery, from the negative pole of that battery to the positive pole of the other and from the negative pole to ground through the key switch, the reason that its not charging may well be that the generator has lost its polarity, to polarize the generator again you need to switch on the key, leave the engine stopped use a piece of wire and momentarily connect the BAT terminal and the Gen terminal for a split second on the regulator,(see the picture at the link below) start up and check the ammeter in the dash to see if its showing a charge, there is also a circuit breaker on the dash that may have popped out so push it back its the little red button. Good Luck
AJ

[Log in to Reply]  [No Email]
AJK

07-20-2007 16:32:31




Report to Moderator
 Re: CAT 955H Generator problem in reply to AJK, 07-20-2007 16:18:56  
Made a typo on the two terminals to cross it should read BAT to ARM
AJ



[Log in to Reply]  [No Email]
Norcal Dave

07-20-2007 16:27:57




Report to Moderator
 Re: CAT 955H Generator problem in reply to AJK, 07-20-2007 16:18:56  
So if the generator isnt polarized correctly, when I test with the multimeter wouldnt it show no charge?

I guess Im confused. Shouldnt I test the batteries with the multimeter first (DC 200)with the motor off. Then test again with the motor running to see if they are charging at about 25V. If they are not, then I know I have a problem at the generator or regulator, at which point I can polorize, which when tested at the battery then should show immediate charging?

[Log in to Reply]  [No Email]
Phil (NJ,Az,Sask)

07-22-2007 07:24:39




Report to Moderator
 Re: CAT 955H Generator problem in reply to Norcal Dave, 07-20-2007 16:27:57  
Norcal dave, I am not familiar with your system but the most common method of using 24V is that a switching method is used to provide 2 batteries in series (24V) for starting, and then charging both batteries switched to parallel from a 12 Volt GEN.

If you have 2 or more solenoids/Contactors that may be your system.

JMHO



[Log in to Reply]  [No Email]
AJK

07-21-2007 05:44:26




Report to Moderator
 Re: CAT 955H Generator problem in reply to Norcal Dave, 07-20-2007 16:27:57  
The multimeter will not show a charge if the generator needs to be polarized, polarize it, start the engine and look at the purpose built in ammeter on the dash, as you increase the engine speed the needle will indicate the amount it is charging, if the needle does not move stop the engine, to verify that the ammeter is functional hold the start switch to the heat position, the ammeter should show a discharge, if it does not the glow plugs are burned out or someone has bypassed the clock, to check if it charging with your multimeter take a reading of the batteries from the positive pole and ground, if the reading is say 24v start the engine and if it charging the voltage will rise by a considerable amount, if there is no change stop the engine turn off the key, remove both the armature (ARM) and field (FLD) wires from the generator, connect a jump wire to the FLD post on the generator to a good ground, connect the voltmeter + cable to the ARM terminal, connect the - side of the meter to ground, start the engine, if the generator is good the voltmeter will follow the throttle. The more engine speed the more output, in order for it to charge the batteries the output voltage from the generator must be higher than that of the batteries, if say you get a reading of 26v + it would indicate that the generator is ok and the trouble is the wiring or the regulator, check what readings you get and come back.
Good luck
AJ

[Log in to Reply]  [No Email]
Norcal Dave

07-30-2007 09:11:06




Report to Moderator
 Re: CAT 955H Generator problem in reply to AJK, 07-21-2007 05:44:26  
I was finally able to get back up to the CAT and do some preliminary testing although not as much as I would like to have done.

So its a 24V system with (2) 12V batteries in series. The newest (upper) battery shows 11.80Vdc and the lower battery shows 12.38Vdc (measurements taken directly on battery posts with digital multimeter). This is without having been charged and not having been run in 2 weeks. The upper battery is a maintenance free CAT battery, but the lower showed hydrometer readings of 1.225/1.205; 1.240/1.235;1.230/1.240 (again not charged). I cleaned the battery posts and cable terminals extensively and recinched the cables to them, repairing some rub damage as the neg cable passed through the lower battery box.

On preheat the Vdc dropped to 6.99 and 8.99 respectively (the ammeter shows a discharge of 10). On Start the Vdc dropped to 8.64 and 7.97(the ammeter shows a discharge of 5).On start there is not enough juice to start it, and it only clicks.

So I see 3 wires that connect to the generator, although they are all painted over. I don't see a regulator anywhere. I wasn't able to start it (because I didnt have two cars to jumpstart with and its nowhere near power to charge the batteries) so I couldnt raise the bucket to bury my head in there.

Where is the regulator located? I couldnt find any sort of regulator box to try to polarize it. The dash board only has the guages in it (from having looked when the guages were replaced a while back). Where is it?

Even though the batteries had not been charged, and dont have enough juice to start the tractor without being boosted, what should I expect to see them reading Vdc?

Also there is no red reset button on or near the dash.

Any help would be appreciated.

[Log in to Reply]  [No Email]
dallas gronefeld

07-20-2007 13:40:50




Report to Moderator
 Re: CAT 955H Generator problem in reply to Norcal Dave, 07-20-2007 10:47:41  
could be bad field coil in starter. I had 4 955h hilifts.If it is the starter I have two new rebuilt with new sol. never been on tractor. phone # 636-441-6951, iam in the st.louis, missouri area.



[Log in to Reply]  [No Email]
Norcal Dave

07-20-2007 15:12:58




Report to Moderator
 Re: CAT 955H Generator problem in reply to dallas gronefeld, 07-20-2007 13:40:50  
I don't know a bunch about automotive electrical work, but if I'm able to jumpstart the tractor, wouldnt that mean that the starter works just fine? I could be wrong, but logically it tells me that the problem is upstream of the starter at either the battery or the generator.



[Log in to Reply]  [No Email]
Art Hotchkiss

07-20-2007 11:49:48




Report to Moderator
 Re: CAT 955H Generator problem in reply to Norcal Dave, 07-20-2007 10:47:41  
Your regulator may be the issue. You can test the generator however by disconnecting the field wires from the regulator and applying 12v to the field while rotating the generator. If you can find a way to change the voltage to the field (6v battery) you can change the output voltage of the generator armature. As a generator is also a motor, with the generator mounted on a bench (well secured) you can apply voltage to the field and armature and the generator should rotate at it's nameplate rated speed. This assumes you are fortunate enough to have the nameplate information.

[Log in to Reply]  [No Email]
[Options]  [Printer Friendly]  [Posting Help]  [Return to Forum]   [Log in to Reply]

Hop to:


TRACTOR PARTS TRACTOR MANUALS
We sell tractor parts!  We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]

Home  |  Forums


Copyright © 1997-2023 Yesterday's Tractor Co.

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy

TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters

Website Accessibility Policy