|
A failed/failing temp compensation board (voltage stabilization circuitry) that piggybacks on the main instrument cluster circuit board is well known for such problems in 240s of your vintage. Although I see some notes they weren't introduced until 1986, yours may still have it. A quick feel up behind the cluster will soon tell you. Do a search here and on other sites for more on that, including how to simply bypass it. Art Benstein's page on this is excellent with lots of pics
https://cleanflametrap.com/tempFaker.html
You wouldn't be the first to replace half your cooling system when it's just that troublesome little board. Rather than throwing parts at a problem like this, an infrared temp gauge would be useful to monitor block temp during and after warmup to see if gauge movement matches actual block temp change. Also to see how uniform the rad core is in case there are significant blockages. Basic ones aren't that expensive. Even a cheapie in some barbecue parts sections would be useful..
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
|
