4500 RPM Module Trouble Shooting

[todds112]

Trying to diagnose problem with the 4500 RPM Module. Please correct me if any of my assumptions are incorrect.

When I turn on the key I get a flash on the 4500 RPM indicator light. I am told this is a self test of the module. This tells me the light circuit itself is OK. I've never seen it light up other than this flash.

Looking at wiring diagram I see there is an input from the Balast Resistor to the Module. I am assuming the resistor is OK as everything else electrical on the truck works fine.

I also see there is a ground to the module. I am assuming the ground is good as the test light lights (upon key on).

I see there is a small jumper from the module to itself (terminal 4 to 1 of module). Terminal 4 is also where the circuit comes in from the ignition switch.

I took the module apart and visually it looks fine, board not cracked, etc. Cleaned up the connector and put it back together.

What am I missing?

Could the module be giving me a good test light and still be bad? Hate to spend $100 on a module and it be working fine. I am assuming the line from the resistor is the "signal"?

[Jim LaGuardia]

First, why do you think there is a problem as it passes the self test?
If you really feel the need to test it just put your truck in 1st gear and accellerate till the engine is screaming away. As the engine overspeeds you will notice a loss of power, this is the module grounding out the ignition to slow it down and should also illuminate the light.
If you are using a tach from SAV, it is NOT ACCURATE. I have found these tachs to be off by as much as 800 rpm.

[todds112]

I've never seen it light up. I've gone down a few of these mountain roads in low gear and it was screaming like crazy. Never came on. I've run it pretty fast on the highway (60 MPH+) and never seen it even flicker.

I've never noticed what seems like the ignition grounding out. Maybe I'm just a woose and have never wound it up that high. Sure don't want to blow her up.

[Erik712m]

Had mine a little over 70mph after i had my lighted driveline installed for a test before the light came on the engine. noise was so load it was you could hardly think.

[Jim LaGuardia]

The light should come on around 68 MPH for a 6X6, and 72-74 MPH for a 4X4.

[todds112]

The light should come on around 68 MPH for a 6X6, and 72-74 MPH for a 4X4.

I have 34" tires on her, so I'm assuming that means it wouldn't come on until 70 or so?

Maybe I am a woose.

[Jim LaGuardia]

Yes, but I would not want to be in a 712 at that speed

[todds112]

Yes, but I would not want to be in a 712 at that speed

Good point.

[75pinz]

Todd,
I think that one came on once in like second gear or something when I was trying to blast though some drifts. Just FYI. I have had so many Pinz's it's hard to remember. I have never seen one come on in 5th.

[bernhard]

The day I picked up my 712 pinz 4 years ago I had the light come on in fifth. I remember clearly the speedometer going over 100KPH and going to what I would estimate at about 105KPH. The tires were the stock Maloyas. Of course back then I hade no idea what I was doing and now never drive it over the 88 KPH limit.

[David Dunn]

Yes, but I would not want to be in a 712 at that speed

Then be glad you didn't know me back when I had my 712.
67 to 68 was the redline with 33.3" tires.....34" tires would be about 2% faster.
75mph @ 3300rpm with a OD trans ..... frontal mass wouldn't really let it go any faster on a flat freeway.......(it would have been better to fit a 710 transfer case than that trans)

Dave

[Erik712m]

Yes, but I would not want to be in a 712 at that speed

Any thing over sixty in the 6*6 gets the nerves on edge. The four times i have had it over fifty was after the drive line was replaced and three of them were going down hill. The one time the rpm light came on it took about ten miles to get there on flat straight Kansas Highway we have lots of them

[David Dunn]

Erik
Driving my 712 over 60 never bothered me any......but a Haffy at 50 plus is another thing
Dave Dunn

[todds112]

Right now with this wind and snow it's scaring me going 35 MPH With it's great aerodynamics I was heading into the wind and a big gust came up and nearly stalled me!

[Erik712m]

Dave, you must have some big gonads.