Daily Archives: February 10, 2019

1995 Ford PSOM Repair

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[Wednesday: 3.4 miles; Saturday: ~6 miles including Riverwalk in Columbus]

I had mentioned a couple of weeks ago that we acquired a new full-size van from the university surplus over in Tuscaloosa. It had to be jump started when I picked it up. And the odometer was dead which also resulted in poor transmission shifting. You may recall that I swapped in the instrument cluster from my ’93 F-150 so we could take the van to the Jackson, MS hamfest. That worked.

I then found a couple of youtube videos about repairing the odometer which is called the PSOM. It is a circuit board which mounts on the back of the speedometer. The speedometer itself is a little motor thing which moves the pointer, receiving a signal from the PSOM circuit board; no more “speedometer cable” like in the old days.

The youtube videos talked about replacing some power supply bits on the circuit board. One of the videos even had a list of part numbers to order from Mouser Electronics. I did that and I got the parts swapped in. But the thing still didn’t work (this is the PSOM that came with the van).

So I ordered a used one off of Ebay for 59.95 (or some such). It arrived this week. I was able to get some information about how the board is connected and that helped me figure out how to power it up on the bench. That way I could run it in the comfort of my chair instead of trying to poke at it while sitting in the car with my arms wrapped around the steering wheel.

I had the working one and the broken one. I compared between the two with my multi-meter and discovered a connection was missing on the broken one. I soldered in a small jumper wire, and now the van PSOM works again! Yesterday I installed the van’s instrument cluster back in the van and the truck’s cluster back into the truck.

I don’t know what I’m going to do with the spare I bought off of Ebay.

Also, I created my own youtube video to add to the general knowledge, which might help someone fix theirs.

Under 68,000 miles!
The location of the jumper.

Filed under Ham Radio
Feb 10, 2019
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