I have a 1978 f250 4x4. My gas, temperature, oil pressure gauges all pegged to the right one day. I than replaced the voltage regulator and it worked great for a week or so and than my gauges all pegged to the right a second time. Thinking that my voltage regulator I just bought was at fault I bought a second one. Installed the second regular and it once again failed a third time. My gauges are pegged to the right again. What is causing my problems?

 

I don't know if a dead short would put a load on the IVR and cause it to fail ... or if just defective IVRs? The fact that they work for a while after being changed leads me to believe they are just defective as I think a dead short would kill them much quicker, like "now".

 

I also thought that. They were both Dennis Carpenter dash voltage regulators

 

If a voltage regulator was sticking & causing a dead short, & max voltage, I would think it would pop the gauge fuse.

The regulators can be tested with a battery charger & meter. Its been a while since I've checked one, but I think the procedure is to hook the ground to the mounting tab, 12V power to one of the terminals, (I forget which terminal) meter set for dc volts from the other terminal to ground. The meter should pulse between about 5 & .5 volts, or bounce the needle if using an analog meter.

I'd be looking for a short on the PC board or the wiring harness that plugs in to the cluster.

Unplug the wires to the temp & oil pressure senders & see if the gauges still peg. Fuel sender too, if you feel like crawling under the truck.

 

Thank you guys for you insight. I haven’t looked really close at my printed circuit yet. When I had the instrument gauges out nothing caught my eye.I did order a new one though. I did notice that my temp gauge didn’t peg till after my truck warned up though. I will be looking at everything a little closer when my oem regulator and printed circuit comes in.

 

After giving your problem more thought, I think the problem is low quality, probably chinese replacement voltage regulators. They go bad due to low quality, not a problem on the truck. Just because they are new doesn't mean they are any good.

Pull the wire off the temp sender on the engine. Connect a test light from the wire to a good ground. Turn the key on, the light should blink. If it doesn't blink, but is on constantly, the regulator is bad. You can also hook a meter to the wire the same way & see if the voltage goes up & down, or stays at a constant voltage. It should pulse.

The best replacement is probably a used working vintage regulator. Or a genuine old stock Ford regulator, search eBay for those. I've opened old regulators up, there are points that you may be able to clean if you wanted to try that route.

If you have to drive the truck before you get this fixed, pull the small gauge fuse from the panel. Otherwise you could cook the gauges, PC or power wire.

 

Thank you scottscott you are the best! Thank you for going above and beyond! I will let you know how it goes. I unfortunately can’t get back to my truck for a week or so 😢

 

Dose anyone make a electronic one to replace it with?
That maybe the ticket over the metal can type.

I would also check to see what your ALT is putting out.
I would think if over charging it would make the IVR work harder?
What ALT & Battery you running?
If a 3G and some fancy no lead plate battery wonder if they could be the cause?
Dave ----

 

Welllllllllllll I pulled my dash apart for the 3rd time and found the printed circuit board looked good. I found that my dashboard ground looked good. My alternator is charging at 14 volts. I don’t seem to be blowing any fuses. I bought a oem factory ford voltage regulator off eBay. I’ve now used my truck for the last week and everything work great so far. Fingers crossed

 

Look at the wire going to the gas tank sender. Most times when the regulator burns out there is a short somewhere between the gas gauge and the sender. You may have to run a new wire from the gauge and the sender.

 

yeah I bought a Dennis carpenter VR for instrument gauges and it’s made in China. It looks really cheap so I’m a little afraid to plug in in after all the work and expensive parts I’ve spent on this project.

 

Good question. I know that many of the different styles are made this way, and we sell a lot of them for the '66 to '77 Broncos. I'm fairly certain that both the mounting and the connections are different from the '78 trucks, but there might be someone out there making them.

The problem with these is the same as with anything. If you're lucky they're only adjusted incorrectly from the factory. We usually need to look at every one and adjust them when necessary. When we first started carrying them, I tested ten of them off the shelf and 8 of them read low. Luckily they were of the adjustable type, so I twisted the little bitty adjuster thingy and brought them all up to between 5v and 6v. My memory said that 5v was the correct rating, so I tried to keep them nearer 5v.
No complaints after we started doing that thankfully.

It's just yet another part that we have to take out of the box and fiddle with when we get them. The tail lamps, running lamps and brake boosters all get the personal touch when they come in.
So far about 95% of the light sockets are wired bass-ackwards so that your bright filament is lit when the lights are on, and the dim one lights up when you hit the turn signals or flashers. Only about 20% of the rear lamps are that way, but it's a rare shipment when we get some fronts that are correct.
A sad state of affairs for sure, but it gives us some more job security as long as we continue to catch them before the customer gets them!

Sorry for the rant-tangent. I get that way more and more these days...
But yes, the technology exists for the electronic version of the IVR. So they're probably out there and I just have not seen one for a '70's truck yet.

paul

 

If you can solder, try a 7805 regulator. 3 pins (in,out, ground) and rock steady 5 volt reference.

 

That’s great info, thanks! Is there a discussion thread anywhere that you show an installation?

 

I found it long ago on the slant six or mopar A-body forums.

I assume you could crack open your old mechanical regulator and splice the IC inside.

I bought one at my local radioshack for a couple bucks but never got around to installing it in my Valiant.

Regardless, I have to wonder if any standard aftermarket Ford regulator that can be bought nowadays doesn’t already contain the solid-state IC, that seems to be trend for all old automobile regulators.

I think most Duraspark modules have gone to IC’s to replace the big energy wasting power resistors as well as the old alternator regulators are probably mostly SS now.

So it might be easier just to buy an aftermarket reg for the truck, not sure.