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No "wait to s start" light and no grid heater


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Snow is forecast so of course the truck is on the fritz.

 

It's about 40 degrees out.  Turn the key, "wait to start" light doesn't come on and grid heaters obviously not working.  I have a Quadzilla tuner and if I just leave the key on long enough I can see that the IAT is reading 40 degrees so I know the IAT is working.

 

Even if the relays or grid is broke shouldn't I still see the "wait to start" light coming on for 10 seconds?

 

Is there something obvious I'm missing?

 

 

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I have my relays switched so I can turn them off when I don't want them. When turned off the WTS lite does not come on.

Does your lift pump come on for a second or 2 when the key is turned on? Does the truck start? If not these are tell tell sings of a failing or failed ECM. What year truck?

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1999 2500.  Truck is getting fuel but without the grid heater it's running like crap.  After market FASS lift pump.

 

I've replaced the relays before but I think that even when the relays are broken the "wait" light still comes on. 

 

Seems odd that its not going through the motions and that's why I'm wondering if I'm missing something obvious.

 

It's hard to troubleshoot when I can't turn the key and hold the voltmeter at the same time.

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At 40 deg. mine starts just fine without grid heaters. Runs rough for a few seconds and straightens out. Does yours start but stay running rough, or not start at all? I'll check again to be sure but I'm pretty certain my lite won't come on when the relays are disabled. Can you read battery voltage through the Quad. like I can with my Scangage? If so you can see if they are on or not because it will pull down into the 10-11 volt range. You can see it on the dash gauge too. Any codes in it?

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No check engine light - I'll pull codes this morning.  I'm pretty sure that when I blew my grid relay a few years back the "Wait" light still functioned but nothing happened.  I'm pondering what-ifs and wondering why it might think the heaters aren't needed even though the temp sensor knows its 40 degrees.

 

Thanks all for your help, by the way.

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If it were mine I would check codes first. Then you could remove the 12v+ and 12v- trigger wires from the relays and jump them to the battery and see if the relays energize or not. That would tell you if it's a bad relay or a a bad signal to tell the relay to come on. Reason I say jump both pos. and neg. is I've been told that some years switched the pos. relay wire and some years switched the neg. one. I never did confirm that though.

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Problem solved!

 

Excessive corrosion on the positive battery terminal was blocking high power to the relay through the fuseable links.  Apparently, no high power to relay = no little red "wait" light on the dash. 

 

Power was reaching all other systems so truck would start but nothing was going to the high amp posts on the relay.

 

Than you all very much for your time and help.  I really appreciate it.

 

Mike

One trick I did learn while troubleshooting this is that since it's a good idea to disconnect the main batteries before poking around the grid relay it's hard to test the relay with a safe power source.

 

The two small terminals that trigger the relay, however, are exactly the right distance apart to test with a 9v battery.  Just disconnect one of the high amp cables, put your ohm meter between the two high amp connectors and bridge the two small connectors with a 9v.  Relay click, relay tested, zip zam done.

Edited by OverToyed
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That's the news we love to hear. Thanks for updating!

Now here's a little trick I learned coming here. Clean them nasty ole terminals up and coat them with motor oil. They'll never corrode again :thumbup2:

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