1976 Ford 335 questions/problems

[mhth0727]

I recently picked up a 1976 Ford 335 3 cylinder diesel and have a few things going on that I'm not sure how to resolve.

I have recently replaced the following; starter, alternator, voltage reg, wire harness, dash cluster, tach cable, ignition switch, and engine cut off cable. Battery tests fine under load.

First and foremost the battery is not charging. When I take a reading at the battery it only reads what the battery is currently charged at. Also the battery light on dash is constantly lit at this time. I thought I would have resolved it with replacing all of the charging system but it seems either I'm missing something or connected something wrong. While typing this I need to double check belt tension (will do Monday) but what else can I check? Is there a way to check alternator, volt reg, etc. with multimeter? Not sure if it makes a difference but the trans safety switch is not working (new one with cables on order) so I have the wires jumped currently till switch comes in.

Second issue is my gauge (rpm) is not registering at all. Again the gauge and cable is new. The cable is fully seated and tight at the dash and motor but no needle movement when running. I removed cable from back of dash and its not spinning when detached and motor running. I also removed cable from engine side expecting to see once started movement in the what I believe is the oil pump assy. Going off parts manual I'm guessing it might be something in the oil pump or gear that is in there that the tach cable connects to? Am I right in my thinking? Should I remove this part and tear into it and see if something came loose or broke? Or is there something easier I should check first.

Lastly, oil sending unit...I got a new one since the harness has a spade style connection vs the older round style. How the heck do you get that old one out? It sits so close to the power steering pump. Ive tried using a swivel head with socket and can't get a solid connection to break it free. I tried a set of channel locks as well but again with steering arms, pump, etc. I can't get them on with a good grip to break it loose.

Any advice would be greatly appreciated.

 

[Destroked 450]

335 is an industrial version of the 3600 ag tractor
Sounds like you threw a lot of parts at it, what was the original issues
Where did you get a wiring harness for that model?
Are you sure you got all the wires on the switch and alternator connected correctly
There’s a short cable inside the cap on the engine that the tach cable connects to, that’s the one that usually breaks. You’ll have to remove the oil filter to have enough room to remove and install that cap and to get the short cable back into the oil pump drive
Removing the power steering pump is the easiest way to gain complete access to the oil pressures switch, if you got the longer switch with the blade connector sticking out it may hit the pump canister, the short button switch is there for a reason
You can try removing the switch while you have the oil filter off to repair the tach cable adapter

 

[mhth0727]

335 is an industrial version of the 3600 ag tractor

Ya it took me a while to decode things and figure that out. The guy I bought it from got it in a lot after a neighbor passed away. He said it was a 4000, and when I looked at it I knew it wasn't based on date codes. I was thinking 3600 but the codes didn't align from what I knew. After buying I figured it out to being the 335.

Original issues when I looked at it the dash was not operating at all, hooking a multimeter to battery I could tell it wasn't charging (seller mentioned he had to put battery on charger once), they had no key for ignition so they jumped the solenoid via a screw driver to get it running, and hydraulics would drop under weight but if you adjust the draft it would stay up. Knowing all of this I talked the price down for repairs as well.

I got a top lid seal kit and replaced all the parts for that (that works again with no dropping), had plans to service all other fluids and wanted to address the key and charging issue as well before taking to my property. I don't have the ability once there to properly work on it. So was trying to get it all situated prior to mowing season here in FL.

I ordered a service, parts, and owners manual from Stevens tractors. I used that to get the part number for the harness for the 335 and ordered one up. It came in saying it was for a 2600/3600/4600 and others, Sparex brand. All the wiring matched up with what was currently on tractor. The harness also came with a wiring diagram so I used that to connect it to the new switch (5 pin from harness and switch) and alternator. It starts with the key when bypassing trans safety switch, but it's possible that maybe I have something wired wrong. I need to find a good wire diagram to follow and see if what they sent me was right. Harness had 4 wires for alternator (ground, field, reg, output) almost positive they are hooked to alternator correctly. I can get photos on sunday/monday when I'm back by tractor.

I noticed the cap (the area new cable screws onto) and was thinking it was a part in that. But I wasn't able to figure if what I was looking at in the parts manual was that cable area. I thought about taking that cap off (still need to change oil) and seeing if I can see what the parts look like and match them up in the manual for a number. The only thing I can find with a search in manual is parts in the oil pump but I'm thinking there has to be the cap on top somewhere in there and I can't find it as I'm not 100% sure what they call it. Just realized search your term (tach cable adapter) and it pulls up what I need for that. Thank you so much for that.

The new oil sending unit seems short and should clear but I might just get a new connector for the button switch and change the end of the harness. Hopefully old switch is still good, or make an adapter to go from spade to button and test the old switch first and see if it registers on the dash. I really don't want to remove the power steering pump as I'm not sure what can of worms that might open lol.

 

[used red MN]

Hello mht.., welcome to YT! Looks like DS450 has you covered. The service manual you are getting should have the wiring diagram in it. I will add that a voltage regulator requires a “good” ground to work properly. Not sure how the voltage regulator for your tractor is designed but the proper connection for the ground circuit for the regulator may be what the regulator relies on to work properly. Meaning that proper grounding of the regulator base may not be what it relies on. So in other words do you know where the wire comes out of the harness to ground and is it grounding properly? The ground connection could very likely be at the alternator, the wiring diagram should tell you this.
On you oil gauge with the key on and the wire disconnected from the sender the gauge should read one extreme either zero or full scale. Then with the wire for the sender grounded it should read the opposite. If it doesn’t do this you have a problem with the wiring, connections or the gauge.

 

[mhth0727]

Hello mht.., welcome to YT! Looks like DS450 has you covered. The service manual you are getting should have the wiring diagram in it. I will add that a voltage regulator requires a “good” ground to work properly. Not sure how the voltage regulator for your tractor is designed but the proper connection for the ground circuit for the regulator may be what the regulator relies on to work properly. Meaning that proper grounding of the regulator base may not be what it relies on. So in other words do you know where the wire comes out of the harness to ground and is it grounding properly? The ground connection could very likely be at the alternator, the wiring diagram should tell you this.
On you oil gauge with the key on and the wire disconnected from the sender the gauge should read one extreme either zero or full scale. Then with the wire for the sender grounded it should read the opposite. If it doesn’t do this you have a problem with the wiring, connections or the gauge.

I will look over the service manual this weekend while out of town to figure out the diagram for when I get back.

Trying to remember but I know there wasn't an actual just ground to chassis on the harness. It did have a ground for the alternator and it had a ground for the dash. Then the regulator had a 4 pin plug coming off it that connected to the harness with same style plug. Will check all grounding with a test light as well.

The oil sender reads on the zero side with it not connected. I will see if I can ground it and see if it reads opposite to confirm wiring is good.

Thank you for the info and things to try.

 

[Destroked 450]

Your tractor shouldn’t have a oil pressure guage
It will have a fuel and temperature guage along with a charge light on the left side of the dash and a low oil pressure light on the right, it should also have a air filter restriction light to the left of the oil light
I’ll have to look at the 5600 or 6600 to see about the harness ground but all of my older -000 models have a ground wire that mounts to the bracket the regulator is mounted on

 

[JoeM(GA)]

#24 is the short cable

 

[Destroked 450]

Yes

 

[used red MN]

Yes

DS, that was another member supplying information, not a question from the OP. Now the OP’s have a red banner with OP across the upper left of their avatars. Very nice addition for viewing the forums.

 

[mhth0727]

Thanks for all the replies for help with this. I finally had a chance to look at it again today. All the wiring is connected correctly here is what I found so far.

It didn't appear that the battery ground to the chassis/starter was making a good ground to the chassis. I removed the started and cleaned up the frame area so that the starter/ground now has a solid connection to chassis and chassis is grounded. Looking at the service manual it appears the harness is grounded at the alternator.

With the tractor not running if I ground my multimeter to the alternator frame and touch the positive I get the reading for the battery there. So it appears the alternator is grounded. It never reads higher than what the battery is currently charged to. I can also get a battery reading if I touch the + to output on alternator and - to the neg terminal on alternator.

When I attach multimeter to the field I get no reading of voltage there at all while running. I did a jump test and connected the output + from the alternator to the field bypassing the voltage regulator. The alternator tested good and voltage was climbing as it should with this method.

This leads me to think it's either still a ground issue or maybe even the new voltage regulator. If I hook my multimeter to the + battery terminal and then to the case of the voltage regulator I get a 12.6v reading like at all other points I do this at. So I'm guessing my regulator is grounding but maybe it's not a "good" ground. Wondering if I can ground the voltage regulator to the chassis trying to figure that out without damaging the regulator so if it is just a bad out of the box I can still return it. Watching some videos now to see if/how I can test the regulator with a multimeter to see if it passes or fails.

 

[mhth0727]

Ok so going through the service manual tests for the Charging system this is were I'm at. If anyone can help me decipher this. Still trying to figure out which pin on the regulator is the ground pin so I can see if I can just ground that outside of the harness.

Output and Field Diode Tests
Engine off, r terminal - 0v
Engine on, R terminal 11.2v and O Terminal 12.4. Service manual states this should be within .5v indicating open output diode or diodes. (Not sure entirely what that means if it's alternator or regulator problem). It goes on to state, if R is lower (my case) field diodes is defective. Regulator should increase alternator output up result in overcharging.

Field Voltage Test
Out put tested low 12v but increases when bypasssing regulator.
F terminal with key on reads .5v (service manual indicates it should read 1.5v-3v)
It states low readings indicate low resistance in alternator or high resistance in regulator input circuit or regulator.

Regulator input test
I am unsure which wire is going to which pin off the regulator. The new harness the colors don't match the diagram in service manual so having a tough go at that. But one wire is reading 12.4v (guessing this is the one going to output) and another is 11.3v which guessing is going to the R. With this test it says if the voltage is there and field circuit is not abnormally low, reg is defective. But I'm not sure what to make as the field circuit was low in the above test. Would that point me to alternator then? But what throws me off is when I bypass the regulator the Alternator passes the other test.