Possibly related issues???

[rusty ol ranger]

87 Ranger XLT
2.9/5sp

My gauges have been doing funny stuff. I was freaking out over on the 2.9 forum thinking that my truck was running hot. However, after today i dont think thats the case.

Past week or so the temp gauge and oil pressure would ride about 3/4 way up the normal band, and when you stopped sometimes the temp would climb to the top of normal real quick, then fall again. Ambient temp was 55* or so.

Now, today, its like, 82*. Temp gauge rides just below 1/2, and oil pressure just above half. The temp gauge did climb like usual but only a couple times, but i noticed that the fuel gauge also magically gained 1/4 tank. I sat idleing in the bank drive thru for ~10 minutes and the temp never got above 1/2 way.

Now, whats odd is, the gauges were fine untill i replaced the right turn signal indicator on the dash. Now, after 2 weeks or so that bulb is blown back out (or not working anyways) and the gauges seem to be functioning somewhat properly.

I know the older trucks (like 85 back, atleast Fseries) ran a insturment voltage regulator. Cant find anything bout rangers useing them, but i assume they do. Im wondering if that is fried on my truck? Or in the process of frying?

I have a theory that the gauges spike after stopping because when the RPMs come down the voltage also drops a bit, due to slower alternator spinning, and the regulator overcompensates?

Im pry way out in left field, but its driving me nuts, not so much it does it but not knowing why.

Any input is apperciated.

 

[RonD]

There is a Ground Strap on the back of the drivers side head that connects to the Firewall, this is the Main Ground for all Cab electrics.

This strap is often left off after engine work, make sure it is there, check both heads, and make sure both ends of strap are on clean bare metal, i.e. a good ground

If you can't find it then ADD ONE, ground cable from engine to Firewall

Rangers use a Pulsed 5volt power supply for fuel gauge, the rest are on 12v system, but poor Ground effects all DC voltage

 

[rusty ol ranger]

Ill check that out. I recall seeing it but didnt check its condition. If its broke/rusted/screwed can i just replace it with heavy gauge (like battery cable) wire?

 

[RonD]

Yes, just need a good Cab Ground, doesn't need battery cable size, 14 or 18gauge would be fine, the Big Ground Amps are starter motor and alternator, 70-120amps, which is why the big ground cable to the engine from the battery, cab might get to 20-30amps, most being blower motor, often grounded on firewall


All body and frame parts are painted before assembly and most are bolted together using rubber washers so no reliable grounds unless you add one, which Ford does.
Ground straps are found on rad support(head lights), inner fender(relays), cab(interior electrics), and frame(tail lights, fuel pumps)

 

[rusty ol ranger]

Yes, just need a good Cab Ground, doesn't need battery cable size, 14 or 18gauge would be fine, the Big Ground Amps are starter motor and alternator, 70-120amps, which is why the big ground cable to the engine from the battery, cab might get to 20-30amps, most being blower motor, often grounded on firewall


All body and frame parts are painted before assembly and most are bolted together using rubber washers so no reliable grounds unless you add one, which Ford does.
Ground straps are found on rad support(head lights), inner fender(relays), cab(interior electrics), and frame(tail lights, fuel pumps)

Damn son i need to buy you a beer.

I pulled it in the shop at work today, popped the hood and checked that strap. It looked ok, but i wiggled it a bit (seemed tight) and not rusty, but i wiggled it some, kinda bent the ends a bit and the gauges seemed to be good and steady on the ride home. Ill see what happens over the next few days and keep you tuned in. If it comes back ill replace the SOB.

 

[Still Bill]

"Fix" it anyhow. Voltage fluctuations no good for health of electronics.