underdash starter relay.

[ken]

I'm only getting about 6 months of service out of the underdash started relay on my 1028. I've tried the auto parts china made heater relays and the real GM part. But after about 6 months it burns/sticks and the starter takes off by itself again. I've gotten to the piont of keeping a spare in the glove box. But i'd like to find a more relible relay. Any sudjestions? I've traced the wires both to and from the relay. They look good with no visible breaks in the insulation. And the starter has been both rebuilt and replaced. I just think i'm probally getting low quality parts. Unless i'm missing something?

 

[mangus580]

Ken, just go buy a good 'can' style relay like is used for the glow plugs and swap it in.

 

[m4A1]

Were those relays 12v or 24v?

 

[m4A1]

The relay should be a 12v triggering the 24v. If you use relays rated for 12v you might have arcing in the relay which might be spot welding the contacts.

 

[ken]

Mike i'm thinking of giving that a try. I'm also thinking of putting a inline fuse on the 24V side going to the starter. Mabye it will blow before the relay welds it's self and kills another starter.

 

[mangus580]

Mike i'm thinking of giving that a try. I'm also thinking of putting a inline fuse on the 24V side going to the starter. Mabye it will blow before the relay welds it's self and kills another starter.

If you are using a relay designed for the amount of current going through the wire, you should be fine.

The issue is, the relay used, is more of a HVAC relay. Its not designed for the heavy current you are sending through it in the CUCV starting system.

 

[GreenBull]

I agree that you may simply want to retrofit a 'heavier' duty relay or a relay that has built in contact protection.

Assuming three starts a day and six month life span those relays are only living less than 600 cycles. You have a problem and it's not the relay.

First question is whether the truck starts properly or does it require extended cranking?

Assuming no long cranking required my first recommendation is to make sure that key/ignition switch performance between run to crank and more importantly from crank back to run is right. Any mechanical or ignition switch problem that results in a slow transition in either direction will contribute to relay point arcing. The arc created when relay points open is more destructive so you want to concentrate on the transition from energised to deenergised.

The problem could be as simple as something interfering with the ignition switch rod. A weak spring in the ignition swith or a pile of sand in the rack/lock housing would do similar.

I suggest that if no problem identified with the above and you are good with a DVOM and basic automotive electrical testing that you make sure you have no voltage drops, transients, or other circuit faults on both the control and load sides. Load includes both the starter solenoid +24 and ground circuits. As I said above you want to check the transitions. Do the circuits energise and deenergise properly? Measure the peak current flow in the solenoid circuit. High current flow will cause the relay points to be closer to their melt point while closed resulting in the normal contact opening arc doing more damage. Dynamic voltage testing is prefered for identifying voltage drop and poor connections in high current flow circuits.

Something I've had demonstrated to me repeatedly is that the battery acts like a shock absorber in a vehicles electrical system. I've seen batteries that started a car and held a charge just fine cause some strange things. With two batteries in series they should be matched. Missmatched batteries or one partialy failed battery could potentialy cause more contact point arc than normal and still crank the engine and hold charge just fine.

Good luck!

 

[ken]

Id have to say it starts pretty quickly. There isn't any extended period of cranking to get it running. A hot start is very quick. You can barely hear the starter work before it's running. It's only got 19k showing on the speedo and drives like a new truck. I've tried the original part from GM. I got the part # off the original one and went to the dealer. It even had the right bracket on it to bolt it to the dash. It didn't last any longer than the cheep auto parts store brand. I don't think the starter is the problem. It's been both rebuilt and replaced. Me not being te only one to have this problem i figured the relay might just be under engineered for the task. I like mikes idea of using the glow plug realy for the job.

 

[mangus580]

I agree that you may simply want to retrofit a 'heavier' duty relay or a relay that has built in contact protection.

Assuming three starts a day and six month life span those relays are only living less than 600 cycles. You have a problem and it's not the relay.

Yes... the relay is WAY under-rated for the application.

 

[IRWFO]

Listen to Mike. I know a lot of CUCV owners in person and on the net. We all had the problem and we all fixed it the same way. A nice HD solenoid under the dash. None of us have burned one out yet since. The only thing I see has been the common cause is when we installed the Gear Reduction Starters.

 

[Sarge]

Not meaning to hijack this thread, however, I have noticed something strange going on.
Everybody on Steel Soldiers is aware of new members who sign up and say, well basically, nothing. After 3 months these new members have 4,000 posts all consisting of "Cool" or "Way to go, dude". Or much worse, they often give bad (technically incorrect) advice. Other members frequently trust a member with 4,000 posts without knowing the history of the poster.
So now we have a new member, "GreenBull". Has anyone else noticed this guy?
I count 9 posts from him. His posts are technically correct and exhaustingly comprehensive when addressing an issue. Quite refreshing and amazing!
So, GreenBull, let me be nosy......
Are you an ASE certified Master Mechanic?
Did you ever run a Motor Pool?
Do you have a degree in Vehicle Maintenance?
I bet one (or more) of the above is correct.
My hat is off to you, not only for the assistance you gave me with my dragging CUCV brakes but also for the above relay advice. I am also certain that you are going to be a great Steel Soldiers asset because you are bringing a lot of technical knowledge to us.
Only one small piece of advice, 'Consider your audience'. That is not meant to be derogatory to anybody, however I have met some super smart vehicle mechanics who did not have a clue how electricity works. The huge majority of the public would not know the difference between an electron or a zener diode if either one bit them in the a$$.
GreenBull, welcome aboard and I hope you post often!
Cool and way to go, dude!
-Sarge

 

[HardCorps79]

Does anyone have a recommended part number for a heavier duty starter relay? I was going to pick up the original from NAPA, but after reading this thread, I want to be sure I don't end up having to buy a replacement in another couple months.

 

[doghead]

Does anyone have a recommended part number for a heavier duty starter relay? I was going to pick up the original from NAPA, but after reading this thread, I want to be sure I don't end up having to buy a replacement in another couple months.

I haven't installed it yet(plan to tomorrow but, I chose this: NAPA part #, 7-01860-1 (SME line). It is rated at 200 amps intermittent. It is a small starter solenoid/relay used in lawn-tractor applications. Cost $15.88

Others use a "Ford" style starter relay.

Either should be fine

 

[realm]

Well how do you wire it up then or is it a direct plug and play?

 

[doghead]

I will cut off the original plug, and install a ring terminal on each of the 4 wires. They attach to the new relay on a stud. I will try to take pics when I do this. I'll post it afterwards.

 

[realm]

Please do...
I'm surprised no one has done this yet though. Has everyone just been replacing the relay with the standards and just kept on replacing them everytime they break? I'm surprised there isn't a HD plug and play one.

If don't mind cutting the wires as long as I have a relay part# and instructions.

 

[m4A1]

I have never had any problems with the relay on either one of my cucv, M1008 or M1028.

 

[davo727]

Im going to give one of these a try SS598T starter solenoid for a 97 ford f350 7.3 diesel $7.78 at rockauto. Im thinking if it will start a 445 cubic inch ford it should work for us.

Dave

 

[doghead]

I haven't either, but I want to feel confident, when others drive it, I won't have to worry about the common starter run-on problems.

 

[m4A1]

Here's an idea, do away with the relay altogether and replace it with a push button switch on the 24v wire. You push the button and the starter will engage, release and starter disengages. The 12v wire would be disconnected.