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Topic: 5V Cluster regulator/ Fuel Gauge Sender (Read 982 times) previous topic - next topic

5V Cluster regulator/ Fuel Gauge Sender

I thought I heard about people replacing the 5V regulator ( the metal can on the back of the cluster PC board) with a commercial 5V regulator... I thought the reason was is that this regulator misbehaves and causes the fuel and temperature gauge to simultaneously drift around on occasion.  I'm thinking this is a bad idea  :nono: , because...

I have measured two clusters, including the one that I had in the car which was working and it looks like these things put out voltage pulses, not as constant DC.  :hick:

It seems to make sense too, as the fuel sensor (for buttstuffog gauge) is 12-83 ohms or so, which means if it was a constant 5V you are putting nearly 5V/12ohms, or 0.4 Amps into the gas tank just to read the fuel sensor.  That does not sound right to drain so much current just for a fuel tank measurment...

The buttstuffog fuel gauge is very slow moving, so you don't see it bouncing with the voltage pulses, instead it just averages the pulses, thereby saving the battery a wasteful 0.5 Amp draw, as the average current will be much lower.

I only put this out there because I finally had to replace my leaking fuel sensor sender (along with tank, pump while I was at it), and had to put in the sender meant for a digital cluster (as the buttstuffog one isn't available, see http://www.foxtbirdcougarforums.com/showthread.php?t=2283 ), and was thinking about ways to make a conversion circuit to make the buttstuffog gauge read correctly again..


V6->V8HO 88 LS
5.0L V8 87 XR7

Re: 5V Cluster regulator/ Fuel Gauge Sender

Reply #1 –
Everyone I've heard that did the 5v regulator conversion have said it works, but the gages read tool low. I checked into it and a 6v reg (7806) is available but thats going to increase the current in the circuits. Also the reg has to heat sinked fairly well so it is seeing a fair amount of current.

Me, I just said fornicate it and installed a aftermarket cluster with a volt meter.... Problem solved.

Re: 5V Cluster regulator/ Fuel Gauge Sender

Reply #2 –
BondoCougar: When you replaced your sender, did you throw the old one out? If you only replaced it because it was leaking you could just swap the "wiper" from the old unit onto the new one.

You'd need some kind of inverter to convert the digital sender reading into one the buttstuffogue cluster could read. This is because the buttstuffogue cluster uses a low resistance (closer to zero ohms) at full and a high resistance at empty, while the digital cluster uses low resistance for empty and a high resistance for full.
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Re: 5V Cluster regulator/ Fuel Gauge Sender

Reply #3 –
Quote from: TurboCoupe50
but thats going to increase the current in the circuits. Also the reg has to heat sinked fairly well so it is seeing a fair amount of current.


Yes, I'm thinking its not a good thing to have the 0.5A or so running thru the wiper in the tank that was probably designed for the low duty voltage pulses that the stock regulator puts out.  Pretty wasteful on battery current too compared with the stock set up.  A few short pulses of 0.5A is much better than a constant 0.5A draw you will get with those linear regulators. I'll put it on the scope and put it here.  The average voltage could then be calculated and I bet its average is probably >5V which would be why the 5V regulator modification would read low.


Quote from: Thunder Chicken
When you replaced your sender, did you throw the old one out? If you only replaced it because it was leaking you could just swap the "wiper" from the old unit onto the new one.


I saved it, but I thought it might be a bad idea putting the ancient one back in.  It seemed to have some noisy/intermittent spots on it when I had hooked it to an ohm meter.  The thought of having to drop the tank again to possiblty have to replace it again didn't appeal to me.  :hick:  I shoulda done what TurboCoupe50 did with an aftermarket approach.

I thought in the long run I should be able to figure out how to do the inverter, but now I'm surprised to see the system is pulsed. :disappoin


V6->V8HO 88 LS
5.0L V8 87 XR7