crazy oil pressure
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Mountain Pass
Joined: Mar 2002
Posts: 190
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crazy oil pressure
I have a '90 F150 w/ 5.8L XLT Lariat. I have the actual oil pressure gauge, not just an idiot light. Sometimes the pressure shows a bit low and when I turn the A/C on max w/high fan or turn the headlights on the pressure gauge picks back up. I've replaced the sending unit and the Ford dealership said there isn't any sort of voltage regulator for the instrument cluster. Is my gauge just going bad? Has anyone else had this same trouble? I want to keep OEM gauges - I'm not interested in an add-on.
Thanks in advance for your help.
Thanks in advance for your help.
Posting Guru
Joined: Jan 2003
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From: Still under the hood in O
Post Fiend
Joined: Jun 2001
Posts: 5,228
Likes: 5
From: Running Springs CA
crazy oil pressure
You a loose connection that makes the gauge move when there is a voltage change.
You need to change your sending unit in order to make your gauge read correctly. See my posting in the thread "Oil Pressure Gauge" in this forum.
Jim
You need to change your sending unit in order to make your gauge read correctly. See my posting in the thread "Oil Pressure Gauge" in this forum.
Jim
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Mountain Pass
Joined: Mar 2002
Posts: 190
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crazy oil pressure
I tested the gauge by grounding to the battery and the gauge worked perfectly. When I hooked the wire back up and started the truck it showed low again, but when I kicked on the A/C it picked back up. Do I have a short or loose wire somewhere? Where should I be looking?
If I were to convert to the "real gauge":
Which sender should I buy (1986 for 351 w/electronic oil pressure gauge or....?)
Which resistor on the back of the instrument cluster is the one I'm going to jumper, and what am I going to jumper it to?
If I were to convert to the "real gauge":
Which sender should I buy (1986 for 351 w/electronic oil pressure gauge or....?)
Which resistor on the back of the instrument cluster is the one I'm going to jumper, and what am I going to jumper it to?
Fleet Mechanic
Joined: Aug 2001
Posts: 1,526
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From: Round Rock, TX
crazy oil pressure
I got a sender for an '84 just to be sure. It will look like a small canister; it's quite a bit larger than the pressure switch.
There will be a 20 ohm resistor directly behind the oil pressure guage. You will jumper across this resistor--one end of the jumper wire on each side of the ceramic cylinder.
There will be a 20 ohm resistor directly behind the oil pressure guage. You will jumper across this resistor--one end of the jumper wire on each side of the ceramic cylinder.
Fleet Mechanic
Joined: Aug 2001
Posts: 1,526
Likes: 0
From: Round Rock, TX
crazy oil pressure
It's hard to say. But it will read in the "normal" region. And it will vary with engine speed and oil temperature, just like a real oil pressure guage. If you want a totally accurate reading, then just install a $15 aftermarket guage.
