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Lift pump voltage before OPS

New OPS yesterday and no voltage to lift pump with the truck running when I probe the LP power wire down at the pump. I suspect a bad OPS. I have 13.5v at the pump with the engine running, can run the pump by crossing terminals with the relay removed and can also power the pump by unplugging the OPS and crossing the two outermost terminals in the pigtail (center terminal is for the gauge). New OPS ordered to replace the "faulty" one.

Here's another issue, though - I called and talked with Bill Heath today about this to run it by him and he gave me the P/N for a heavier OPS that they use. The P/N of the OPS my dealer gave me is 1924-4500 and the one Bill recommended is 1924-4501. I don't know the difference and neither did the dealer. A good friend that has a parts store brought up that it could be that one is normally closed and one normally opened. If so, then that could explain why it doesn't work on my truck. I guess I'll find out tomorrow after I pick up the replacement OPS.
 
Replacement OPS did the trick.

Now, back to this relay idea modification. I haven't found pictures of this. Does anyone have any I could see, so I can get an idea of where the relays got mounted and to give me an idea of what the end product looks like?

On the diode, what am I asking for when I go to the store?
 
I just use self tapping metal screw and put it wherever it is convenient for the cables to reach on the firewall.
 
I have pictures on here of the install on the 95 Tahoe and the 94 K3500 someplace. I prefer to use a relay socket to wire to. As opposed to attaching the wires directly to the relay. That way if you wish to pull the relay for any reason, you don't have to worry about getting all the wires back on the correct posts. In the dark at -20

I got my relays at the local GMC dealer for $4 or $5 iIRC.
 
I ordered the sockets yesterday morning and just have to find a couple relays. I decided on this due to neatness and the same reason you mentioned. The relays are hard to find with a diode, but I located the 30A I need at Grainger. They're $20 each, which seems a little salty. With little knowledge about diodes, though, it may be my only safe method.
 
Did you check your local truck dealers? At the dealership I went to, they said they only keep the diode style and OEM replacements in stock It was a combination dealership for Semis and GMC. They lost their GMC dealership when GM restructured. One of those running in the black dealers that got cut out.
 
Planning on the double since I can find a relay with a diode included. I would have no idea what to ask for in searching for a diode at the local electronics shop.

The question, now, is am I looking for a SPDT relay or a SPST relay? I've located both types and just don't know which one I need for this.

Local dealership has nothing unless I have an application I can tell them, for which the relay is used.
 
Use SPDT.

The way I understand it is the SPDT can become SPST depending on how you use it.

SPST cannot become SPDT. SPDT is more universal.

I could be wrong, though.
 
i HAD THE SAME QUESTIONS AS YOU. i DIDN'T HAVE A CLUE WHAT i WAS LOOKING FOR. lUCKILY THE COUNTER guy at the local dealership knew what I needed.. I did wire the plug upside down the first time.

Might try a local parts store. I can try to get a number off the relays I used.

Somewhere it is posted which relay to use. Maybe message Buddy and ask him direct.
 
jrsavoie said:
i HAD THE SAME QUESTIONS AS YOU. i DIDN'T HAVE A CLUE WHAT i WAS LOOKING FOR. lUCKILY THE COUNTER guy at the local dealership knew what I needed.. I did wire the plug upside down the first time.

Might try a local parts store. I can try to get a number off the relays I used.

Somewhere it is posted which relay to use. Maybe message Buddy and ask him direct.
Click to expand...

Already thought of that, but he cannot accept PMs, so I don't know how to contact him unless he reads this thread.

If you have a number/brand on your relays, then I can find out what they are.

SPDT - http://www.colehersee.com/home/item/cat/199/RC-400012-DS/

SPDT - http://www.grainger.com/Grainger/ww...relay+diode&N=0&GlobalSearch=true&sst=subset#

It seems to me these are doing the same thing.
 
I will go out and see if I can find another set. Daughter has the truck. The wife was just here with the Tahoe having issues. Turned out to be the fuse was loose in the inline fuse holder that I installed when I did the dual lift pump relay. I was right there and all I was concerned about was figuring out why the Tahoe wasn't running right.
Very weird thing the fuse being lose in the fuse holder. I've never seen that before on anything.

THe relay and socket info needs to be in a sticky with the dual lift pump relay schematic
 
As said in post #32, SPDT is more universal, the difference is that 86A post is not there for SPST.

It is doing the same thing with the way it is wired.

SPDT is easier to get and more universally available.
 
I will start another thread with some pictures of what I'm doing on this in a few days. It will include a link back to this one, in the event someone wants to see where this came from, in the future.
 
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