ICVR Problem or Other?
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ICVR Problem or Other?
HELP FMC400! LOL
This is on my '76 Crew Cab:
I've spent half the afternoon trying to get my fuel and temp gauges working. By all indications I needed a new ICVR. Took the dash apart, installed a new one from DC, and still nothing.
I've got voltage at the ICVR. Test light lights up dim on gauge screws on the back of the cluster, and when I probe the back of the cluster connector. However, I've got no light at either the fuel sender or the temp sender. I've traced the wiring as much as I can without disassembling the entire dash. I found the orange wire bullet connector behind the headlight switch (I have dual tanks on my Crew) and there is no voltage there either. The fuel tank switch DOES work.
As far as I can tell, all connectors are tight, all wires are intact. Both gauges SHOULD work now, but they don't.
I don't like running without a working temp gauge, but I've got cattle to move and two sea containers to deliver in the next few days. I'm probably missing something simple, but I can't figure out what it could be.
This is on my '76 Crew Cab:
I've spent half the afternoon trying to get my fuel and temp gauges working. By all indications I needed a new ICVR. Took the dash apart, installed a new one from DC, and still nothing.
I've got voltage at the ICVR. Test light lights up dim on gauge screws on the back of the cluster, and when I probe the back of the cluster connector. However, I've got no light at either the fuel sender or the temp sender. I've traced the wiring as much as I can without disassembling the entire dash. I found the orange wire bullet connector behind the headlight switch (I have dual tanks on my Crew) and there is no voltage there either. The fuel tank switch DOES work.
As far as I can tell, all connectors are tight, all wires are intact. Both gauges SHOULD work now, but they don't.
I don't like running without a working temp gauge, but I've got cattle to move and two sea containers to deliver in the next few days. I'm probably missing something simple, but I can't figure out what it could be.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Let's look at this in terms of voltages rather than test light brightness. What voltage do you measure on BOTH sides of the studs on the back of the temperature gauge?
If this is a new ICVR from DC, chances are it's a linear regulator instead of PWM, meaning you can read the output with a common multimeter. If it's an original style with the trimming ****, you'd have to watch test light flashes instead. That would make the above instructions invalid.
If this is a new ICVR from DC, chances are it's a linear regulator instead of PWM, meaning you can read the output with a common multimeter. If it's an original style with the trimming ****, you'd have to watch test light flashes instead. That would make the above instructions invalid.
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Thanks for the reply, FMC.
I'll try to get voltages tomorrow. I hadn't read that you could use a multimeter on the new ICVRs until this evening. Had other work to do this afternoon, so I had to leave this for now.
Could you tell me what I'm looking for when I check the voltage? It seems there has to be something in common with these two gauges other than the ICVR or else at least one of them would be working now. *Forgot to say earlier, I installed a new sending unit in the seat tank this afternoon as well. Old one was positively bad.
I'll try to get voltages tomorrow. I hadn't read that you could use a multimeter on the new ICVRs until this evening. Had other work to do this afternoon, so I had to leave this for now.
Could you tell me what I'm looking for when I check the voltage? It seems there has to be something in common with these two gauges other than the ICVR or else at least one of them would be working now. *Forgot to say earlier, I installed a new sending unit in the seat tank this afternoon as well. Old one was positively bad.
Last edited by VocaTexas; Oct 1, 2013 at 09:06 PM. Reason: add content
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
If the ICVR is an electronic retrofit (the one I got from LMC was), then one of the studs should read a solid 5 volts DC. The voltage on the other stud depends on the loading from the sending unit downstream, but will not be more than 5 volts DC. It could fall below 5 volts DC depending on what the sending unit is doing. It will be zero if the gauge is open-circuit. Alternatively, the voltages at the two studs will be equal if the sending unit is disconnected in some way.
If the ICVR is electromechanical, you'll have to look for a once-per-second pulse with a test light on both sides. These are a little harder to troubleshoot. Your description makes it sound like you have an electronic retrofit, though.
Further reading for those interested: https://www.ford-trucks.com/forums/1...-the-icvr.html
If the ICVR is electromechanical, you'll have to look for a once-per-second pulse with a test light on both sides. These are a little harder to troubleshoot. Your description makes it sound like you have an electronic retrofit, though.
Further reading for those interested: https://www.ford-trucks.com/forums/1...-the-icvr.html
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Yeah, the one I got from DC doesn't have the trimmer on it.
I'll try to get those voltages tomorrow if I have time. The next four days are going to be busy, so it might end up having to wait until next Monday.
Thanks for the help.
I'll try to get those voltages tomorrow if I have time. The next four days are going to be busy, so it might end up having to wait until next Monday.
Thanks for the help.
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