grid heaters stick on

[fest3er]

Originally posted by sewman

If my heater solenoids ever fail I think I'd try Ford starter solenoids,has anyone tried them yet?

Bob

I was thinking of using them today, but I likely won't use them. Reason? Those solenoids are usually designed for short-term use, not up to the 3. 5 minutes the heaters can stay on.



I've done some more investigation today. Stancor make a relay designed for continuous duty that will handle 200A (586-902 for 12V control or 586-903 for 15V control). These are designed for use in electric winch applications, among others.

They warn against using the 12V unit in an application where the charging system brings the voltage above that, such as in our trucks. However, since the heaters draw the voltage down, I believe the 12V model will be the best.



However, they *do* cost around $60 each from Newark, and I'd need two of them, unless I wanted to trust the service manual - which says the heaters only draw 95A each - and use only one. If 25 of us were to get together, we could get the price down to about $40. Also, the lead time is 42 days!



More pondering is required. Anyone else have any ideas?



Fest3er

 

[illflem]

Fest3er, how about using a starter solenoid. I've seen them used on winches and electric motor powered snow plows, they are basically just relays. You can pick up generic ones pretty cheap, should last a long time.

 

[fest3er]

Originally posted by illflem

Fest3er, how about using a starter solenoid. I've seen them used on winches and electric motor powered snow plows, they are basically just relays. You can pick up generic ones pretty cheap, should last a long time.

I'm getting closer to this option. However, Allied Elec. has some 100A Stancor contactors (120-902) that may well do the trick. And they're only $15. Strange, though, they look *very* similar to the OEM relays.



The reason I'm shying away from starter relays is they aren't necessarily rated for continuous duty. Even though the heaters cycle on and off, they *can* be on for up to 3. 5 minutes. ... Wait, that's the *total* time the heaters are cycled; the duty cycle is still 10-30 seconds on, and perhaps up to 5 seconds off. That's not a bad duty cycle. I *have* gotten the heaters to stay on for a longer period of time by revving the engine up so the intake air stays cold; but this is a rare occurrence.



If the starter relays are *really* cheap (like $2 or less), I'll try a couple, provided mounting them isn't too difficult. I've rarely encountered a Ford with a failed starter relay! And they *should* be designed to operate in the temperature range usualy found under the hood.



But I think I'd still rather spend the $15 and install relays rated for continuous duty. The one thing holding me back from these is the temp range (-20F to 120F); seems to me the under-hood temp can easily exceed these limits. And do I pick the 12VDC control, or the 15VDC control? If the system voltage does not stay higher than 21V or so for very long (as I suspect, given the current draw), that model would be OK. But if the system voltage stays over 12V during operation, I would have to pick the 15V model, which makes it questionable as to whether the relay will *stay* contacted during operation.



Hmmm.



I think I'll run out and get a couple cheap starter relays. They rarely fail, they work in the temps typically found under the hood, and they should stand up to the heater duty cycles. If they're $5 or less, I won't mind replacing them once a year, if needed.



All right. You've convinced me. I'll try the starter relays. And I'll let y'all know how they work. (Now to find a couple with 5/16" studs!)



Fest3er

 

[fest3er]

I've gone and done it. I ordered a couple Stancor model 120-902 relays from Allied Electronics. They should arrive in a couple weeks.



Visually, they are similar to the OEM relay. These relays are slightly larger than the OEM relays, have silver alloy contacts, and are rated for continuous duty. They are 100A relays good for 400A in the first 1/2 second. They cost about $15 each.



They're good for 50,000 close/open cycles at the rated 100A load, at 2 cycles per minute. Assuming that our trucks cycle the heaters up to 4 times per minute, these relays should still be good for around 25,000 cycles. So, assuming 4 cycles per minute, two minutes of heating per start, two starts per day for 6 months of the year, they should last at least five years. They may last even longer, as the life is probably calculated at the max ambient temperature of 150F, whereas the heaters only operate when the ambient temp is 50F or less. Time will tell how long they last.



At $30, they're less than half the cost of the DC part, although some fabrication may be needed to mount them to the OEM bracket. At that price, I won't mind so much replacing them every four years or so.



I'll post again once I have them installed and working.



As a side note, I did buy a couple starter relays, but they would draw about 4A through the coil, which, IMHO, is too much to be pulling through the PCM. Also, the starter relay do not have isolated coils; one side is grounded to the mounting plate, which would aggravate the installation. So I'll have to return them. And they cost about $7 each; for double the price, I'm getting relays that more closely match what the truck wants.



Fest3er

 

[ADSmith]

I tried one of the generic Ford starter solenoids wired to a toggle switch to be able to manually control the supply to the factory relays. Apparently the coil is not rated for continuous duty because it fried within a month. I ended up fixing my problem by bending the grippers inside the connector on the intake temp sensor so that they would make better contact.

 

[Scot]

I have used the Ford style solenoids for winch applications. They do tend to stick rather frequently under constant duty use. The best thing I have found is a constant duty solenoid made by Standard Ignition. Part # SS496 (unless they have changed it in the last few years. ) It mounts on the same mount as the Ford type and will trigger either with ground or power. It should be in stock at any auto parts store carrying Standard Ignition parts.

 

[w-cummins]

Originally posted by fest3er

I've gone and done it. I ordered a couple Stancor model 120-902 relays from Allied Electronics. They should arrive in a couple weeks.



Visually, they are similar to the OEM relay. These relays are slightly larger than the OEM relays, have silver alloy contacts, and are rated for continuous duty. They are 100A relays good for 400A in the first 1/2 second. They cost about $15 each.





I'll post again once I have them installed and working.



As a side note, I did buy a couple starter relays, but they would draw about 4A through the coil, which, IMHO, is too much to be pulling through the PCM. Also, the starter relay do not have isolated coils; one side is grounded to the mounting plate, which would aggravate the installation. So I'll have to return them. And they cost about $7 each; for double the price, I'm getting relays that more closely match what the truck wants.



Fest3er

So did/do these work ?? did you use the 12 volt models or the higher voltage model? BTW the ECM runs them not the PCM

 

[w-cummins]

Originally posted by w-cummins





So did/do these work ?? did you use the 12 volt models or the higher voltage model? BTW the ECM runs them not the PCM

oops... . I just looked ( 12 valve ) you don't have an ECM on your truck so in your case the PCM does control them

 

[fest3er]

Originally posted by w-cummins So did/do these work ?? did you use the 12 volt models or the higher voltage model?

Oops. Seems I forgot this thread.

Yes, I got them installed and operating. They are still working just fine. They have a more satisfying 'clunk' when turning off than did the OEM relays. It's only been a few months, so I can't report on how long they will last.

I used the 15VDC relay. They operate down to 10VDC, IIRC. If my batteries drop *that* low, I won't have enough juice to crank it over, never mind complete a pre-heat cycle.

Visit http://home.adelphia.net/~npmrphy/relay.pdf for a page of installation instructions and part sourcing info.

Fest3er