Hey fellas, I'm having a small electrical issue that I just can't figure out. When I turn on the turning signals, it causes my temperature gauge to rise steadily, I thought my truck was having an overheating issue, so replaced EVERYTHING except the radiator which I had serviced and pressure checked, I know that it's not overheating, if I don't use the signals, it stays right in the middle as it should, but use the signals and it climbs steadily up to H, once the signals are off, it slowly drops back down to normal. Anyone have any idea what could be causing this issue?...

 

That's a new one on me. Definitely NOT a common problem. Here's the fix, however. You have a short in the harness between the turn signals and the temp. gauge wire that is going to ground. Run the harness and look for worn spots or spots that are rubbing up against anything metal. Keep in mind to check the column and the panel itself. Good luck!

 

Alright, I'll check the harness and see what I can find... So is there any specific place I should check first?... I guess I'm having a problem understanding how they could affect each other, I would think they would be completely seperate all the way thru, just having a hard time understanding how this could happen...lol Not sure if it could be related, but I restored my gauge panel a few months ago, everything works fine, but I noticed about a month ago that the dash gauge lights are no longer working, the lights in the gear shift and heater controls all light up though, could this issue possibly related to the other?...

 

There's an IR drop upstream of your ICVR. Does it also happen with the wipers on?

 

I haven't checked the wipers, but I'll try to remember to do so when I get home tomorrow... A little new here, not sure of the verbiage you got there, "IR", "ICVR"?...lol

 

Sorry for not being very descriptive. The dash gauges are powered by a small device called an Instrument Cluster Voltage Regulator (ICVR). It and the turn signals are powered from the same pole of the ignition switch, meaning they share a common source. If one affects the other negatively, it's an indication that there is unwanted electrical resistance toward the source. When current is pulled through the resistance, it induces an unwanted voltage drop - one robs power from the other. "IR drop" is a term used to describe this drop (IR = current multiplied by resistance - Ohm's law). Such a problem appears regularly in other areas - for example, more common problems with interaction between turn signals and running lights or brake lights.

The wipers are also part of the accessory circuit, so their behavior could give a clue as to where the problem lies.

More info on the ICVR: https://www.ford-trucks.com/forums/1...-the-icvr.html

 

The turn signals ARE separate, but all it takes is two wires running near each other in the harness to rub through on the same piece of metal and bang, they're connected.

There's only TWO dash lights in the cluster. (one on either side of the speedo) It's very possible you have two bad sockets or bulbs. It's REAL common to have a broken plastic cluster that won't hold the sockets against the printed circuit board. Be very careful playing around with 37 year old plastic that was only designed to last 6 years.

 

It's very possible that one of the turn signal indicators is interacting with the gauge because of a printed circuit or cluster connector fault - note, however, that this would be limited to the turn signal indicators, not "dash lights" - which I associate with nighttime illumination. I didn't notice anything in this thread about dash illumination specifically. This thread is about turn signals and the temperature gauge.

I wouldn't go so far as to say the turn signals are separate, because both loads (turn signals, ICVR) are powered by the accessory bus upstream. For example, a near-failure accessory fuse (with extra resistance) would cause the issue described here. Hence the request to try it with the wipers on to eliminate the obvious. The wiper motor is a heavy enough load to easily incriminate or eliminate this possibility before moving on to more complicated work (like taking out the cluster).

 

Well I did get some time this last weekend to check out the wiper theory, and no go, I replaced all the fuses checked the harness from the sending unit back to the cab, all good... When the trucks driving around the gauge works fine, but when you use the signals, it rises slowly but constantly... And for some reason the cluster still won't light up, yet the remainder of the accessory lights turn on, heater, etc...

 

What does "no go" mean specifically? I might not have been clear the first time, but with the turn signals OFF, see if the act of turning the wipers ON affects the position of the needle.

If there is no interaction, then there's something going on with the back of the cluster - likely a weak short on the printed circuit along the lines of what earthquake68 described. You'll have to pull to investigate. The cluster illumination problem is likely related (bad printed circuit, broken cluster mounting holes, etc).

 

As per the no go, I turned on the wipers with the signals off and the needle didn't move... So I was merely saying that it probably wasn't related, and I'd have to agree, it has to be somewhere on the printed circuit for sure... Just in case it's gone bad, does anyone know where to pick up a new printed circuit?..

 

I agree with your thinking. The printed circuit is available aftermarket for most applications, but it's generally very poor-quality material. It will work, but tears easily (especially if the ICVR is removed). You may be able to find an original through an obsolete parts vendor (such as Green Sales) or eBay.

 

Ya, I've already checked Ebay but really not much out there, I'll check with Green Sales, but I'll probably hold off till I can get the cluster back out for inspection... But definitely sounds like the culprit, and I had taken it out a few months back for a restoration, buffed the lens, repainted all the needles, replaced the bulbs, etc., maybe I just didn't get the harness plugged all the way into it?... I know that the lights did work after I completed it, so maybe something just wiggled loose?...

 

The connector having wiggled loose would explain the lights out, but not the interaction between the gauge and the turn signals. That's either a physical short on the cluster, or unwanted resistance upstream. The fact that loading the accessory bus elsewhere (wipers) does not cause the behavior seems to point away from the latter and toward the former.

 

Oh alright, then yes, I guess I'll know more (hopefully...lol) when I get it pulled out this weekend... I'll keep you informed... Thanks again for all the help, two heads are better than one...lol