Hey guys, I gots me an AirDog II 165. I installed it back in September and have been with this quirk since then. I'm not sure if it is a problem or anything but just wanted to see if others experience this?I got my fuel pressure at 20psi according to my fuel pressure gauge. When I start the truck and the grid heaters kick on, the fuel gauge will go down to 15-16psi. When the grid heaters switch off, the fuel jumps back up to 20 psi. I have watched the fuel in the line move back and forth to the gauge as they switch on and off.Its a mechanical gauge with a cage protector in between the stock fuel filter housing and gauge.WOT never shows fuel pressure to be lower than 15psi on the gauge.

The psi drop with the grid heaters on is normal. But, mine only drops 1-2 psi when mine kicks on. Don't know if you have aproblem with your 4-5 psi drop. Hopefully someone with an AirDog will chime in.

My pressure never changes really... Cold start the fuel pressure will be a bit lower but no change from grid heaters. Once it warms up it back to 19 PSI at idle and 17 psi WOT...

So I wonder if I'm having a problem with the airdog or my fuel pressure gauge then?

I have the ADII 165 and do not experiance a pressure drop with the cycling of the heaters. My question would be where are you getting your power for the pump from? My relay is plugged into the oe harness for the oe lift pump and the 12v power comes off of the alternator. If you are wired into another power source that is affected by the heater cycling you would get a voltage drop to the pump and lower pressure during their cycles. That would be my thought anyway.

I'm tied to the power lead in the PDC box for my AirDog and the ground wire to the body... Nothing tied directly to the battery.

I have had a weird problem with mine (150) for a while also. Sometimes it has 17.5 then a little while later it will be 14.5 then back up to 17

I'm tied to the power lead in the PDC box for my AirDog and the ground wire to the body... Nothing tied directly to the battery.

What trips your relay?

Eureka! I never even gave that a thought! My pump is connected to the passenger side battery for power. They said not to because of corrosion problems, but I maintain that. That makes total sense now as to why it does it then.

Might be the reason. But if i remeber correctly that was one of the power options listed in the instructions. Move it and see what happens.

Oh, I know it was an option they listed. Buy they said it was not necessarily a good idea because of the whole potential corrosion problem. It makes sense.. if the grid heaters switch on, the battery voltage will drop because of the draw. Hence why the volt meter drops. When the volts drop, the airdog pump does not have 12volts like it should. Less voltage, lower pump pressure. When the grids kick off, the alternator brings the battery voltage back up and the pump runs off of the 12 volts it need to run it at the regulated pressure. :lol:Preachin to myself here...

What trips your relay?

ECM... Still hooked to the ECM for trigger on and off but the pump power is in the PDC box not the batteries...

Oh, I know it was an option they listed. Buy they said it was not necessarily a good idea because of the whole potential corrosion problem. It makes sense.. if the grid heaters switch on, the battery voltage will drop because of the draw. Hence why the volt meter drops. When the volts drop, the airdog pump does not have 12volts like it should. Less voltage, lower pump pressure. When the grids kick off, the alternator brings the battery voltage back up and the pump runs off of the 12 volts it need to run it at the regulated pressure. Preachin to myself here...

True the volt drop with pull down all accessiores. You might have the batteries load tested just to verify they are good. Maybe why I don't see like many others is because my electrical system and batteries have always been kept up... Here is my article on my fresh batteries...

I bought 2 brand new batteries from NAPA at about the same time I put the airdog in.

Ok... Now then start looking at doing a voltage drop test...

Just throwing this out there. I connected mine to the alternator and do not experience the voltage drop when they are cycling. Am I isolated from the voltage by being connected there?

Just throwing this out there. I connected mine to the alternator and do not experience the voltage drop when they are cycling. Am I isolated from the voltage by being connected there?

That is where mine is hooked at and my volts drop. I don't know why there is a difference. I remember a big thread on this topic quite some time ago but, I can't find it. Must not be searching for the right words!

Ok... Now then start looking at doing a voltage drop test...

Not sure what you mean with that link you provided...

D'Oh! Feed cable voltage drop testing...

Close, but no ceeeegarrrr!

I goota eat alittle crow here. Though i had never noticed any pressure drop while the grids were cycling, I watched mine closely yesterday and this morning and sure enough there was a change. When they come on I loose about 1/2 to 3/4 of a pound of pressure. Just never noticed before.

MMMmmm... ****** chickens! No racial pun intended!I have not had a chance to administer this test yet... Although, even though I suffer a decrease in pressure, even with it drained down, I still never have it go below 15psi.